Digital Exciter

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EX2000 PWM Digital Exciter User’s Manual

EX2000 PWM Digital Exciter

User’s Manual GEH-6375 Issue Date: June 1997

These instructions do not purport to cover all details or variations in equipment, nor to provide for every possible contingency to be met during during installation, operation, operation, and maintenance. If further information is is desired or if particular problems arise that are not covered sufficiently for the purchaser’s purpose, the matter should be referred to GE Motors & Industrial Systems. This document contains proprietary information of General Electric Company, USA and is furnished to its customers solely to assist that customer in the installation, testing, operation, and/or maintenance of the equipment described. This document shall not be reproduced in whole whole or in part nor shall its contents contents be disclosed to any third party without the written approval of GE Motors & Industrial Systems.

� 1997

by General Electric Company, USA All rights reserved.

Printed in the United States of America


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SAFETY SYMBOL LEGEND

WARNING Indicates a procedure, practice, condition, or statement that, if not strictly observed, could result in personal injury or death.

CAUTION Indicates a procedure, practice, condition, or statement that, if not strictly observed, could result in damage to or destruction of equipment.

NOTE Indicates an essential or important procedure, practice, condition, or statement.

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WARNING This equipment contains a potential hazard of electric shock or burn. Only personnel who are adequately trained and thoroughly familiar with the equipment and the instructions should install, operate, or maintain this equipment. Isolation of test equipment from the equipment under test presents potential electrical hazards. If the test equipment cannot be grounded to the equipment under test, the test equipment’s case must be shielded to prevent contact by personnel. To minimize hazard of electrical shock or burn, approved grounding practices and procedures must be strictly followed.

WARNING To prevent personal injury or equipment damage caused by equipment malfunction, only adequately trained personnel should modify any programmable machine.


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TABLE OF CONTENTS Section/Subject

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CHAPTER 1. OVERVIEW 1-1. Description Scope ....................................... 1 1-2. Introduction ................................................. 1 1-3. EX2000 System Overview.......................... 3 1-3.1. Hardware Design...................................... 3 1-3.1.1. Control Core (Regulator Module) ......... 4 1-3.1.2. Power Converter Module ...................... 5 1-3.1.3. Optional Hardware Modules................. 5 1-3.2. Software Design ....................................... 6 1-3.2.1. Software ................................................ 6 1-3.2.2. Ac and Dc Regulators........................ .... 6 1-3.2.3. Scaling................................................... 7 1-3.2.4. Faults.....................................................7 1-3.2.5. Simulator ............................................... 7 1-3.3. Human-Machine Interface........................ 8 CHAPTER 2 HARDWARE SYSTEM DESCRIPTION 2-1. Introduction ................................................. 9 2-2. Packaging .................................................... 9 2-2.1. Environmental .......................................... 9 2-2.2. Enclosure..................................................9 2-3. Ratings......................................................... 9 2-3.1. Input Ratings ............................................ 10 2-3.1.1. PMG Input............................................. 10 2-3.1.2. Auxiliary Bus Input............................... 10 2-3.1.3. Bus Feed From the Generator ............... 10 2-3.1.4. Dc Input Power...................................... 10 2-3.2. Output Current Rating.............................. 10 2-3.3. Voltage Control Range............................. 11 2-3.4. Power Profile Rating ................................ 11 2-4. Power Converter Hardware......................... 12 2-4.1. Ac and Dc Input Drives............................ 12 2-4.2. Dc Link and Dynamic Discharge ............. 13 2-4.3. IGBT and IAXS Devices.......................... 13 2-4.4. Output Contactor MDA............................ 13 2-4.5. Output Shunt SHA....................... ............. 13 2-5. Control Electronics Module ........................ 14 2-5.1. TCCB (DS200TCCB) .............................. 14 2-5.2. PSCD (DS200PSCD) ............................... 14 2-5.3. GDDD (IS200GDDD).................... .......... 15

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2-5.4. PTCT (DS200PTCT).................................. 15 2-5.5. NTB/3TB (531X305NTB) ......................... 15 2-5.6. LTB (531X307LTB) .................................. 15 2-5.7. RTBA (DS200RTBA)................................ 15 2-5.8. ACNA (DS200ACNA)............................... 15 2-6. Inputs and Outputs......................................... 15 2-6.1. Generator Inputs ......................................... 15 2-6.1.1. Potential Transformer Inputs................... 15 2-6.1.2. Current Transformer Inputs..................... 16 2-6.2. 4-20 MA Inputs .......................................... 16 2-6.3. Generator Line Breaker Status ................... 16 2-6.4. Generator Lock-Out Trip............................ 16 2-6.5. Additional I/O............................................. 16 CHAPTER 3 SOFTWARE SYSTEM OVERVIEW 3-1. Introduction ................................................... 25 3-2. Configuration Tools ...................................... 25 3-3. Programmer Module...................................... 25 3-3.1. Using the Programmer................................ 25 3-3.2. Software Design ......................................... 26 3-4. Standard Function.......................................... 26 3-4.1. Automatic Voltage Regulator (AVR) Ramp.............................................. 26 3-4.2. Automatic Voltage Regulator Setpoint ...... 26 3-4.3. Automatic Voltage Regulator..................... 26 3-4.4. Field Regulator (FVR) Ramp ..................... 26 3-4.5. Field Regulator ........................................... 27 3-4.6. Under Excitation Limiter (UEL) ................ 27 3-4.7. Over Excitation Limiter (OEL) ................. 27 3-4.8. Firing Block................................................ 27 CHAPTER 4 SOFTWARE CONFIGURATION AND SCALING 4-1. Introduction ................................................... 37 4-2. Configuration and Scaling Example.............. 37 4-2.1. Example Generator, Exciter and Regulator 37 4-2.1.1. Generator Data......................................... 37 4-2.1.2. Exciter Data............................................. 38 4-2.1.3. Regulator Data......................................... 38

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4-3. Generator Configuration .............................. 38 4-4. Feedback Scaling.......................................... 39 4-4.1. Generator Feedback...................................39 4-4.1.1 Potential Transformer Failure Detector (PFTD) Operation.................................. 40 4-4.1.2. PTFD Scaling ........................................ 40 4-4.1.3. PTFD Detection Level........................... 40 4-4.1.4. P.T.U.V.................. ................................ 40 4-4.2. Bridge Voltage Feedback ......................... 40 4-4.3. Bridge Current Feedback.................... ...... 41 4-4.4. Feedback Offsets ...................................... 41 4-4.5. Instantaneous Overcurrent Trip................ 41 4-5. Regulator Scaling ........................................ 42 4-5.1. Automatic Voltage Regulating System .... 42 4-5.1.1. AVR Operation....................... ............... 42 4-5.1.2. REF1 Operation..................................... 42 4-5.1.3. REF1 Scaling and Configuration .......... 42 4-5.1.4. Autosetpoint Block................................ 43 4-5.1.5. Autosetpoint Block Scaling and Configuration.........................................43 4-5.1.6. Automatic Voltage Regulator (AVR) Block......................................... 44 4-5.1.7. AVR Scaling and Configuration ........... 44 4-5.1.8. AVR Proportional Gain......................... 45 4-5.1.9. Integral Gain.......................................... 45 4-5.2. Under Excitation Limiter (UEL) .............. 45 4-5.2.1. UEL Operation ...................................... 45 4-5.2.2. UEL Scaling andConfiguration ............. 46 4-5.2.3. UEL Curve........................ ..................... 46 4-5.3. Reactive Current Compensator (RCC)..... 48 4-5.4. VAR/Power Factor Control...................... 49 4-5.4.1. VAR//PF Control Operation and Configuration........................................ 49 4-5.5. Field Regulator (FVR) ............................. 50 4-5.5.1. REF2 Operation..................................... 50 4-5.5.2. REF2 Scaling and Configuration .......... 50 4-5.5.3. FVR Operation ...................................... 50 4-5.5.4. FVR Scaling .......................................... 51 4-5.5.5. Transfer Tracking Meter and Balance... 51 4-5.6. Field Current Regulator (FCR) ................ 51 4-5.6.1. Alternate FCR........................................ 52 4-5.6.2. Alternate Field Current Regulator Scaling .................................................. 52 4-5.6.3. Primary FCR.......................................... 53 4-5.6.4. Primary Current Regulator Scaling and Configuration ................................. 53 4-6. Optional Functions Scaling and Configuration.............................................. 54

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4-6.1. Transducer Outputs ....................................54 4-6.2. Ground Detector and Diode Fault Monitor ......................................................55 4-6.2.1. Ground Detector and Diode Fault Scaling and Configuration ...................... 55 4-6.3. Field Thermal Model.................................. 56 4-6.3.1. Thermal Model Operation....................... 56 4-6.3.2. Thermal Model Scaling ........................... 56 CHAPTER 5 STARTUP CHECKS 5-1. Introduction ................................................... 57 5-2. EX2000 Prestart Checks................................ 57 5-2.1. Energization and Simulator Control Checks........................................................ 57 5-3. Pre-Start Power Checks................................. 59 5-4. Initial Roll Off-Line Checks.......................... 61 5-5. On-Line Checks............................................. 62 5-6. Operator Interface.......................................... 63 5-6.1. Units with UC2000 or IOS......................... 63 5-6.2. Units with Discrete Switches and Meters... 63 CHAPTER 6 SIMULATOR SCALING AND OPERATION 6-1. EX2000 PWM Simulator .............................. 65 6-1.1. Simulator Scaling ....................................... 65 6-1.2. Operation .................................................... 67


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CHAPTER 1 OVERVIEW 1-1. DEFINITION AND SCOPE This manual describes the EX2000 Pulse Width Modulated (PWM) Digital Regulator for brushless generator excitation systems. This is a microprocessor controlled power converter that produces controlled dc output for rotating exciter, brushless generator applications. This manual is intended to assist applications and maintenance personnel in understanding the equipment hardware and software. It also provides initial startup information. The manual is organized as follows:

Chapter 1 – Overview Briefly defines the EX2000 PWM regulator with an overview of the hardware and software design. Includes references to other manuals and documents, one-lines and connection diagrams.

Chapter 2 – Hardware System Description Contains specific information on system hardware design and purpose, ratings, I/O definition.

Chapter 3 – Software System Overview Contains specific information on software tools, structure, functions, and one-line representations.

Chapter 4 – Software Configuration and Scaling Gives examples of the scaling for specific parameters in a generic brushless regulator generator application.

Chapter 5 – Startup Checks Contains pre-start, startup, and on-line adjustments required during the commissioning of the PWM regulator for a brushless excitation system.

Chapter 6 – Simulator Scaling and Operation Gives example simulator scaling and operation instructions for a typical brushless regulator generator application.

1-2. INTRODUCTION The EX2000 PWM regulator controls the ac terminal voltage and/or the reactive volt amperes of the generator by controlling the field of the rotating brushless exciter. Figure 1-1 shows a typical oneline system of a PMG fed brushless generator application. Power for the regulator is normally supplied from a Permanent Magnet Generator (PMG) driven directly by the main generator field. This can be a single phase or three phase PMG. An alternative method is to obtain excitation regulator power from a Power Potential Transformer (PPT) supplied from an auxiliary bus. This can also be a single or three phase supply. The PPT is required to ensure an ungrounded input to the regulator. A second power source is also possible from a dc battery source.

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The control system contains both a generator terminal voltage regulator and an exciter field current regulator. These are known as the automatic or ac regulator and the manual or dc regulator respectively. When operating under control of the dc regulator, a constant exciter field current is maintained, regardless of the operating conditions on the generator terminals. When operating under control of the ac regulator, a constant generator terminal voltage is maintained under varying load conditions. If the generator is connected to a large system through a low impedance tie, the generator cannot change the system voltage appreciably. The ac regulator, with very small variations in terminal voltage, then controls the reactive volt amperes (VARs). If the generator is isolated from a system, the ac regulator controls the terminal voltage and the VARs are determined by the load. Most systems operate in a manner that is between these two extremes. That is, both VARs and volts are controlled by the ac regulator. Normal operation is with the ac regulator in control, with an automatic transfer to the dc regulator in the event of loss of potential transformer feedback as detected through Potential Transformer Failure (PTF) or PT Undervoltage Detection (PTFD).


In the EX2000 PWM regulator, PT Failure Detection requires two sets of PT inputs. There is automatic tracking between the ac and dc regulators to ensure a bumpless transfer in either direction. A balance signal is available for display on the operator station or turbine control interface. A transfer between regulators can be initiated by the operator or, if supplied, by the PT failure detection algorithm. In addition to the reference input to the ac regulator summing junction, a number of both standard and optional inputs are possible. See section 1-3.2.2. Besides the regulating functions, the excitation system contains protective limiter functions, startup and shutdown functions, and operator interfaces that are implemented in both hardware and/or software. The software is accessed via an RS-232C communication link by using the SuperTool 2000 (ST2000) program or GE Controls Systems Toolbox for Windows NT or Windows 95. These toolkits are microprocessor based software used to configure and maintain GE’s EX2000 regulators and exciters. It consists of a collection of programs (tools) running under a command shell. The EX2000 PWM regulator includes a Local Area Network (LAN) and RS-232C interfaces for external communication, which includes using the ST2000 toolkit that can be purchased separately.


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Figure 1-1. PMG Brushless Exciter Overview

1-3. EX2000 SYSTEM OVERVIEW 1-3.1. Hardware Design The EX2000 PWM hardware consists of a control core and a power converter section, described in Chapter 2. The controller includes printed wiring boards containing programmable microprocessors with companion circuitry, including electricallyerasable programmable read-only memory (EEPROM) where the regulator’s system blockware pattern is stored.

The power converter consists of input disconnects and filters, a dc link with charge control, IGBT devices, output contactor and shunt, and control circuitry. There are also optional hardware devices available on the EX2000 PWM such as 4-20 ma transducers, Power Potential Transformers, and Field Ground Detector Power supplies.

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1-3.1.1. CONTROL CORE (REGULATOR MODULE). Referring to Figure 2-3 the control core is mounted in two board racks on the outside of the core panel and is accessible while the regulator is operating. Also, behind the hinged outer door, several Input/Output (I/O) boards are mounted. (See Figure 2-4) The control core consists of all these circuit boards interconnected by ribbon cables and harnesses, which keep wiring to a minimum. Detailed hardware information including fuse and test point information, replacement instructions and board layouts are provided in the referenced documents for each of the following circuit boards. Power Supply and Contactor Driver (PSCD) Instruction Book GEI - 100241 The PSCD board creates internal power supplies and redistributes the necessary power supply voltages for the other control core circuit boards. An isolated 70 V dc supply is also produced and used for LTB board inputs. The PSCD board also produces the contactor coil voltage for the MDA output and charge control contactor. Gate Driver and Dynamic Discharge (GDDD) Instruction Book GEI - 100240 The GDDD board controls the gating of the IGBTs for bridge output and Dynamic Discharge control. It also isolates and scales DC output, DC link voltage, shunt feedback and heat sink temperature feedbacks. LAN Terminal Board (LTB) Instruction Book GEI - 100022 The LTB board provides an interface between control devices and external devices such as contactors, relays, indicators, lights, pushbuttons and interlocks. Microprocessor Application Board (TCCB) Instruction Book GEI - 100163 The TCCB contains software transducering algorithms that mathematically manipulate the


inputs from the isolation and scaling printed wiring boards. These inputs are analog feedback signals from the current and voltage transformers, which monitor generator output and line voltage, and from the bridge ac input and dc output voltages and shunt feedbacks. I/O Terminal Board (NTB/3TB) Instruction Book GEI - 100020 The NTB/3TB board includes an RS-232C communication port for connecting to a personal computer (PC). The optional field ground detector inputs are connected to the NTB board. Drive Control and LAN Control Board (LDCC) Instruction Book GEI - 100216 Reprogramming the LDCC board Instruction Book GEI - 100217 The LDCC controls LAN communication and permits operator access and control via the Programmer keypad. It also contains the drive control microprocessor which monitors start/stop sequencing, alarms, trips and outer loop regulators and motor control microprocessors which monitors the field voltage and current regulators, gating and overcurrent protection. Relay Terminal Board (RTBA) Instruction Book GEI - 100167 The RTBA board provides seven output relays with form C contacts available for customer use which can be driven from a remote input or directly from the relays on the LTB board. ARCNET Link (ACNA) The ACNA board provides the connection point for the ARCNET Lan communications


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1-3.1.2. POWER CONVERTER MODULE

Figure 1-2. EX2000 Brushless Unit

The power conversion section consists of an input section, a dc link, and the converter output section. The input section is a three phase diode bridge with input filters. The range of the ac input is from 90 volts rms up to 275 V rms. Frequency inputs range as high as a nominal 360 hz. It can be a single phase or three phase input from a PMG, auxiliary bus or generator terminal fed. An input PPT is not required for the PMG input. A PPT is required for an auxiliary bus or generator terminal feed. An optional voltage doubling feature is available for units requiring higher forcing capability. An optional backup source from nominal 125 or 250 V dc batteries is filtered, diode isolated and combined with the three phase diode bridge output. These sources charge the power capacitors through a charge control resistor, RCH, which forms the dc link portion of the power converter module. The dc link is the unregulated source voltage for the control core power supplies and the output power through the IGBTs. A coarse control of the voltage level of the dc link is provided by the dynamic discharge circuit. This circuit will dissipate excess power from the dc link (possible due to a regeneration effect from the field of the rotating exciter) through

the dynamic discharge resistor, RDD. This circuit is normally powered from the PSCD board but may be powered through the dynamic discharge power source resistor RDS if control power is lost. The converter output section takes the dc link source voltage and pulse width modulates it through the IGBT devices. The output voltage is determined by the following formula: Voutput = Vinput * (time on/(time on + time off)) where Vinput is the dc link voltage, time-on is the conduction time of the IGBT devices and time-off is the non-conduction time of the IGBTs. The chopping frequency of the IGBTs is approximately 1000 hz. See Figure 5-1. This output is fed to the rotating exciter field as a regulated voltage or current. A single pole contact from the MDA contactor isolates the regulator from the field. An output shunt monitors the field current.

1-3.1.3. OPTIONAL HARDWARE MODULES. There are a limited number of structured options available with the EX2000 PWM regulator. Up to

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four 4-20 ma output transducers are available for customer use. They are driven from D/A converters located on the NTB board, and are non-adjustable devices. Scaling is provided in the EX2000 PWM software. A 50/60 hz, 25 kVA Power Potential Transformer (PPT) is available for units that are connected to an auxiliary bus or generator output terminals. This PPT may or may not be supplied inside the regulator enclosure. Power to the primary should be fused per the application notes found in the control elementary supplied with the equipment. This transformer is sized to supply rated excitation requirements continuously and still be capable of operation at ceiling excitation for a short time. An optional Field Ground Detector Power supply may be supplied for some systems. This power supply provides 24 V control power to the Field monitor unit mounted in the generator exciter housing. A 120 V ac feed is required to power this supply.

1-3.2. Software Design The regulator application software consists of modules (building blocks) combined to create the required system functionality. Block definitions and configuration parameters are stored in read-only memory (ROM), while variables are stored in random-access memory (RAM). Microprocessors execute the code. Diagnostic software is transparent to the user. A Programmer module with a digital display and keypad allows an operator to request parameter values and self-checks.


These blocks are tied together in a pattern to implement complex control functions. For example, a control function such as the under-excitation limit (UEL) is included as an ac regulator input by setting software jumpers in EEPROM. The relevant blockware is enabled by pointing the block inputs to RAM locations where the inputs reside (the UEL requires megawatts, kilovolts and megavars). The UEL output is then pointed to an input of the ac regulator summing junction. The software blocks are sequentially implemented by the block interpreter in an order and execution rate defined in the ST2000 tools. The blockware can be interrogated while running by using the ST2000 Tools. The dynamically changing I/O of each block can be observed in operation. This technique is similar to tracing an analog signal by using a voltmeter.

1-3.2.2. AC AND DC REGULATORS. The ac or Automatic regulator and, dc or Manual regulator are software functions again emulating traditional analog controls. The ac regulator reference is from a static counter and is compared to the generator terminal voltage feedback to create an error signal. In addition to the reference signal input to the ac regulator summing junction, the following inputs can be used to modify the regulator action. (The power system stabilizer (PSS) is an optional function.) Reactive Current Compensation (RCC). The generator voltage is allowed to vary in order to improve reactive volt amp (VA) sharing between generators connected in parallel. Generator voltage decreases as overexcited reactive current increases, and increases as underexcited reactive current decreases. Alternatively it can be used to provide line drop compensation.

1-3.2.1. SOFTWARE. The exciter application software emulates traditional analog controls. The software uses an open architecture system, which uses a library of existing software blocks. The blocks individually perform specific functions, such as logical AND gates, proportional integral (P.I.) regulators, function generators, and signal level detectors.

Under-excitation Limit (UEL). Under-excited VARs must be limited to prevent heating of the generator iron core and to ensure dynamic stability of the turbine generator. This is done by an underexcitation limiter that takes over when a specified limit curve is reached and prevents operation below this limit.


V/Hz. The ratio of generator voltage to frequency (V/Hz) must be limited. This prevents overfluxing the generator and/or line-connected transformers caused by overvoltage operation or under-frequency operation, or a combination of the two. Power System Stabilizer (PSS). The introduction of a high gain, high initial response exciters can cause dynamic stability problems in power systems. The advantage of these exciters is to provide improved transient stability, but this is achieved at the cost of reduced dynamic stability and sustained low frequency oscillations. The PSS is fed with a synthesized speed signal based on the integral of accelerating power. This indicates the rotor deviation from synchronous speed. This signal is conditioned and fed into the summing junction of the continuously-acting ac regulator so that under deviations in machine speed or load, excitation is regulated as a composite function of voltage and unit speed. The stabilizer therefore produces a damping torque on the generator rotor and consequently increases dynamic stability. The PSS is an optional function. Over-excitation Limiter (OEL). It is necessary to limit generator excitation current off-line to prevent overfluxing the generator and connected transformers. On-line, it must be limited to prevent field thermal damage. The limiting action is performed by the excitation current regulator. The current regulator takes control of bridge gating if the regulator (automatic or manual) calls for a field current that produces main generator field excitation current in excess of a predetermined pick-up level. The dc or manual regulator is configured as a field current regulator using the shunt feed back as a reference compared to the manual regulator static adjust reference. It will maintain a constant exciter field current based on the setpoint adjuster. The on line and off line field current regulators are low value gate selected with the manual regulator output to select the appropriate firing level for the IGBT bridge.

1-3.2.3. SCALING. It is necessary to scale the software in each exciter for application with a particular generator. The regulators use normalized values of counts to represent one per unit (1 pu).

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Typically 1 pu equals either 5000 or 20000 counts. This means that the feedback value for a particular variable, such as field voltage (VDCLINK = 1 pu) or bridge current (AFFL = 1 pu), must be normalized by using a multiplier to equal the prerequisite value of counts when it is at 1 pu. See Chapter 4 for more details.

1-3.2.4. FAULTS. The EX2000 has a sophisticated self-diagnostic capability. If a problem occurs, a fault code flashes in the Programmer display showing a fault name and number. The fault number also appears on the display on the LDCC in coded form. GEI - 100242 includes information on fault codes, interpretation, and troubleshooting.

1-3.2.5. SIMULATOR. Located within the core software is a sophisticated system simulation program that models the exciter and generator behavior. The simulator is activated via a software jumper in EEPROM.

CAUTION The simulator physically operates the field contactors when a start signal is issued to the exciter. If dc link voltage is present, current may flow in the exciter field. Signals representing the field and the generator feedbacks are simulated in the TCCB and fed to the transducering algorithms, in place of the real feedbacks. Once the exciter is scaled for a particular generator, the simulator uses that scaling. For example, after a successful startup sequence is performed in simulator mode, the operator interface will displays the exciter voltage and current and generator voltage applicable to that particular unit. This tool is useful for training, startup, and calibration checkout. Scaling and operation of the simulator is discussed in Chapter 6.

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1-3.3. Human - Machine Interface Each EX2000 PWM will have a human - machine interface (HMI) device of some form. The standard offering will be via a data link with the turbine controller over the Status S page and re gulator information will be obtained through the turbine controllers HMI. Other interfaces offered may


include, but are not limited to, discrete switches and meters, direct DCS control through a UC2000, or some other device. Refer to the control elementary supplied with the equipment for the devices provided and to that device’s specific instruction book for further information.


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CHAPTER 2 HARDWARE SYSTEM DESCRIPTION

2-1. INTRODUCTION This chapter describes the EX2000 PWM regulator hardware structure, and overall operation. When reading these descriptions, refer to Figure 1-2, the specific unit elementary, and the excitation layout diagrams provided with the equipment.

Reactive Sulfur Reactive Chlorine Hydrogen Sulfide Sulfur Dioxide Chlorine Dioxide Sulfuric Acid Hydrochloric Acid Hydrogen Chloride Ammonia

2-2. PACKAGING GEI-100228 provides information on Receiving, Storing, and Warranty Instructions for DIRECTOMATIC 2000 Equipment. This document should be consulted upon receipt of the EX2000 PWM regulator. Each regulator will endure the following environmental conditions without damage or degradation of performance.

2-2.1. Environmental Temperature requirements for the EX2000 PWM should be maintained within the shipping and storage limits in GEI - 100228 during transport and handling. Once installed, the operational limits of an ambient temperature of 0 to +45 °C, outside of the convection cooled cabinet, should be maintained. It is expected that the hottest board entry temperature will be approximately 60 °C allowing the use of 70 °C parts. 5 to 95% relative humidity with no external temperature or humidity excursions that would produce condensation should also be maintained. The EX2000 PWM control equipment is also designed to withstand 10 PPB of the following contaminants:

2-2.2. Enclosure The standard enclosure offering is a NEMA 1 or IP20 equivalent, 90 inches high by 24 inches wide and 20 inches deep. An optional 36 inch wide enclosure is also available. In some instances, just the regulator panel without enclosure will be provided. This panel measures approximately 63 inches high by 17 inches wide by 18.5 inches deep. Other enclosure types are available. Estimated weight is 1200 pounds with NEMA 1, 24 inch enclosure, 900 pounds without enclosure. Estimated watts losses are a maximum 200 watts for all applications.

2-3. RATINGS In the interest of producing a robust design, all power components, including the IGBT package, were chosen with an operating limit of at least 50 A where practical. This overdesign of components should provide the long life and reliability desired in a generator excitation regulator. Each EX2000 PWM regulator has a specific output limit rating based on the application of the regulator and limited by the shunt chosen for the application. The following ratings information is the maximum output of the standard regulator, using a 25 A shunt. For shunt ratings other than 25 A, the output current

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limitations will be reduced proportionately. Name plate information should be used for accurate ratings.

2-3.1. Input Ratings The ac input is the primary input power to the brushless regulator. The range of input ac is from 90 V rms. up to 275 V rms. The ac input may be single or three phase. The input ac may be from a permanent magnet generator (PMG), customer supplied auxiliary bus, or bus fed from the generator. The ac source input to the EX2000 PWM regulator should have an impedance of 6 % nominal based on an estimated 20 A, 10 kVA source.


2-3.1.3. BUS FEED FROM THE GENERATOR. Bus Fed based systems will require an input transformer to isolate the input to the brushless regulator from the power system. This is also to insure that the power source to the brushless regulator is ungrounded. The transformer will be external to the enclosure that houses the brushless regulator. The secondary voltage can range from 90 V ac rms up to a max. 275 V ac rms. Nominal secondary voltages can be 100 V ac rms up to 250 V ac rms. Rated frequency for the bus feed based systems can be 50 Hz or 60 +/- 10 %. If a bus fed system is applied on a black-start gas turbine, this input may start at 20 % of rated speed, therefore, the voltage and frequency will start at 20 % of rated.

2-3.1.4. DC INPUT POWER. The dc source 2-3.1.1. PMG INPUT. The voltage and frequency for PMG based input will start from 0 and increase to rated as a function of generator speed. Rated input from the PMG system can be as high as 250 V ac rms / 360 Hz. Nominal voltages can be 100 V ac rms up to 250 V ac rms. With overspeed conditions, the maximum is 275 V ac rms / 440 Hz. Since the PMG is ungrounded and is only used to source power to the brushless regulator, no input transformer is required. PMG systems on gas turbines will see extended periods of time at < 50 % speed operation on startup. This is due to the purge cycle needed by the gas turbine. Since the PMG may be the only input power to the regulator, the control will initialize at ≤ 60 V ac rms (i.e. ~50% speed).

input power is generally provided from a battery bus. This source is a back-up to the primary ac input power source. It can be used as the primary input power for starting black-start turbine generators. The nominal battery bus voltages are based on a 110/125/ 220 / 250 V dc. Therefore, the operating range for the dc input is from 80 V dc up to a max. of 290 V dc.

2-3.2. Output Current Rating The bridge is capable of delivering the following absolute maximum output: •

25 A dc continuously over the specified temperature range

•

40 A dc for 20 s once every 30 minutes after continuous operation at 25 A dc over the specified temperature range.

2-3.1.2. AUXILIARY BUS INPUT. Auxiliary bus based systems require an input transformer to isolate the input to the brushless regulator from the customer power system. This is to insure that the power source to the brushless regulator is ungrounded. The transformer can be external to the enclosure that houses the brushless regulator but will generally be located in the panel. The secondary voltage can range from 90 V ac rms up to a max. 275 V ac rms. Nominal secondary voltages can be 100 V ac rms. up to 250 V ac rms. Rated frequency for the auxiliary bus based systems can be 50 Hz or 60 +/- 10%.

The PWM bridge is monitored for excessive temperature by a heatsink sensor. Both alarm and trip signals are available.


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2-3.3. Voltage Control Range

2-3.4. Power Profile Rating

The PWM bridge is capable of two quadrant operation (positive and negative output voltage, positive current). This allows operation near zero voltage. The PWM bridge has two active transistors and will operate in zero vector mode. This will allow the output voltage to be chopped in PWM fashion from +V dc to 0 for positive voltage commands and -V dc to 0 for negative voltage commands. The chopping frequency is approximately 1 khz.

The output power profile is a function of line impedance, line current rating, operating point (I dc and V dc), and capacitor current rating. Peak current is limited by IGBT rating. In general higher current output is available at lower output voltages. Output current (I dc) can be higher than line current rating. The regulator shall be capable of matching the following power profile.

The IGBT bridge does not provide a low impedance path which would provide rectification when gating is disabled. This prevents runaway conditions known to occur on brushless units having rotating diode failure. The four flyback diode structure provides this inherently.

The continuous operating area is bounded by the minimum of the capacitor limit, line limit, 25 A dc, or maximum output curve and the x (V dc) and y (I dc) axis. The y axis shows input line amps (rms), capacitor amps (rms), or output amps (dc) for a given output V dc and I dc. The curve labeled 25 shows rms capacitor current on the y axis for a given V dc and 25 I dc.

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Line and capacitor currents as functions of dc voltage and current 35 at 200 Vdc and 25 Adc line current is 15 Arms

IGBT limit 25Adc

30

cap limit 10 Arms

line limit 12.5 Arms maximum output

25

25 Adc

20 Line (A rms), capacitor (A rms), or output (A dc) current 15 25 10

at 50 Vdc and 25 Adc capacitor current is 10 Arms

5

0 0

50

100

150 200 Output voltage (Volts dc)

250

300

350

Figure 2-1. Typical Power Profile

The curve labeled 25 A dc shows rms line current on the y axis for a given output V dc and 25 I dc. The line limit curve corresponds to given V dc and I dc which would result in rated line current. The cap limit curve corresponds to given V dc and I dc which would result in rated capacitor current. The following graph illustrates the various limits.

sheet is typical for all applications. On a requisition basis, the output shunt (SHA), charge resistor (RCH), and dynamic discharge resistor (RDS) may change. Also, various combinations of the input source power may exist. A single phase PMG with battery backup is assumed.

2-4.1. Ac and Dc Input Devices Negative voltage operation is not shown.

2-4. POWER CONVERTER HARDWARE For the following discussions, elementary drawing 03A and the panel layout drawings (Figures 2-2 thru 2-5) should be used references. The elementary

The ac input device DSWAC is a three phase, 600 V ac, 30A molded case industrial circuit breaker. For single phase applications, the L1 and L3 connections should be used. The dc input device DSWDC is a two phase, 250 V dc, 30 A molded case industrial circuit breaker. These input devices are mounted at the top of the panel, easily accessible for operation as a disconnect during equipment maintenance or inspection.


The ac input source is filtered by snubber RC networks and rectified by a three phase diode bridge (DM1, 2 and 3). The dc output of this bridge charges capacitors C1, C2, C3, and C4, forming the dc link. The dc supply is filtered through inductors (LPDC and LNDC) and battery capacitor C1F. It is then fed directly to the dc link through isolation diode DM4. MOV1 and MOV2 are provided for surge protection. All of these components are located at the top of the panel, behind the ac and dc disconnects.

2-4.2. Dc Link And Dynamic Discharge A charge control resistor (RCH) mounted on the heat sink assembly is provided to limit inrush current during power up and capacitor charging. The second pole of the MDA contactor controls application or removal of the charge control resistor. The dc link provides the source power for internal board power supplies via cable DCPL to the PSCD board. The control power supply is designed to operate over a range of 60 to 600 V dc on the dc link. Auxiliary diodes DM5 allow stored energy in the exciter to be returned to the dc link when the output contactor MDA opens. Excessive voltage buildup in the dc link during regeneration is controlled through the dynamic discharge circuit. This circuit monitors the level of the dc link and will dissipate energy through the dynamic discharge resistor (RDD) mounted at the top of the panel to prevent overvoltage of the power circuit and board rack supply. The C leg of the 3 phase IGBT pack is controlled by the dynamic discharge circuitry on the GDDD board. An alternate source of power for the discharge circuit is provided through the RDS resistor, also to the GDDD board, in the event that control power is lost. Jumper settings on the GDDD board set the control level of the dc link by the dynamic discharge circuit.

2-4.3. IGBT And IAXS Devices The dc link also provides the unregulated power source for the Insulated Gate, Bi-polar Transistor (IGBT) bridge used to provide the exciter field current. The bridge consists of legs A and B of the

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three phase, 50 A, 1200 V IGBT pack. Only leg A upper and leg B lower IGBT’s are active. Leg A lower and leg B upper are permanently inactive. Controlled by the microprocessor based digital regulator, the leg A and B IGBT’s are modulated to pulse the dc link supply and feed the resulting output to the field of the rotating brushless exciter. The output voltage is determined by the following formula: Voutput = Vinput * (time on/(time on + time off)) where Vinput is the dc link voltage, time on is the conduction time of the IGBT devices and time off is the non-conduction time of the IGBTs. The chopping frequency of the IGBTs is approximately 1000 hz. The IAXS board provides the connection of the dc link capacitors to the IGBT bridge, dynamic discharge control and gate control from the GDDD board. The IAXS board is also the connection point for the dc output voltage and sensing feedbacks to the control circuitry.

2-4.4. Output Contactor MDA The output contactor MDA is described in GEK 83756. It is a double pole, single throw, 600 V dc, 50 A contactor, isolating the positive leg of the EX2000 PWM bridge output. The second pole is used to remove the charge control resistor RCH. The power for the contactor coil is provided from the PSCD board. This voltage is only present when the control has been commanded to run. When the DC link voltage is not present, there is no power available to drive this contactor.

2-4.5. Output Shunt SHA The output current is monitored by the control via the 100 mv feedback shunt SHA. The shunt rating is application specific. A range from 1 A to 25 A maximum is possible. The shunt rating must be less than twice the exciter amps full load.

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2-5. CONTROL ELECTRONICS MODULE

2-5.1. TCCB (DS200TCCB)

The control electronics module contains powerful programmable microprocessors with companion circuitry, including EEPROM, to process the application software. It is a module assembly that is located on the front door assembly of the power conversion module. Elementary diagram sheet A04 and Figure 2-7 shows the connections of the various boards in the control module.

The microprocessor application board (TCCB) is essentially a transducer board. The isolated and scaled generator PT and CT signals are fed from the PTCT board to the TCCB board. The TCCB uses voltage controlled oscillators (VCOs) to transform the analog voltage signals into digital signals. Software transducers process the voltage and current signals and then calculate generator data. This information is passed to the LDCC control processors for use by the regulators. The EX2000 PWM simulation software also resides in the TCCB.

This control module assembly contains the main processor board (LDCC), microprocessor application board (TCCB), power supply and contactor driver board (PSCD), and the gate driver board (GDDD). These boards are interconnected through ribbon cables. The following is a brief functional description of the boards within the exciter. Each board has a unique GEI which documents the hardware layouts, test points, fuses and other information for each individual board. These are referenced in Chapter 1. The LAN and Drive Control Board (LDCC), which is the main processor board, provides the IGBT gating circuit control and regulator functions including: •

Automatic voltage regulator

•

Field current regulator

•

Field current limit regulator

•

Volts/hertz limit regulator

•

Reactive current compensation

•

Under-excitation limit regulator

Optional functions include: •

VAR/power factor regulator

•

Power system stabilizer

The LDCC board also contains both isolated and non-isolated circuits for communication inputs to the exciter’s controller. The LED display and keypad programmer is on this board.

2-5.2. PSCD (IS200PSCD) The Power Supply and Contactor Driver board (PSCD) is powered from the dc link via stab-on terminals DCPL1 (+) and DCPL2 (-). The control operates from 80 - 400 V dc as nominal range inputs. Transient operation to 600 V dc is possible during maximum operation of the dynamic discharge. This board produces control power for distribution to the other control module boards. The main supply produces +/- 24 V, +/-15 V, and +5 V for control boards (LDCC and TCCB, etal.) A 17.7 V ac squarewave is distributed through high frequency transformers to the gate driver and LTB inputs power supplies. Auxiliary to the main supply are supplies for generating isolated 70 V dc (sufficient to power 13 LUP inputs ) and an isolated SHVI/SHVM power for future applications. The contactor control power supply from the PSCD board is sized to deliver up to 0.75 A dc. Power is taken directly from the dc link and converted to 105 V dc by a buck converter. The enable of the MDA contactor is via an optically coupled signal which is logically in parallel with the coil of K1. Relay K1 is driven from the LDCC board when the control is commanded to run. Relay K86 is used as the controls permissive to run and emergency stop. Dropping out K86 will immediately stop the EX2000 PWM regulator. Coil voltage is from the 70 V dc power supply on the PSCD board.


2-5.3. GDDD (IS200GDDD) The Gate Driver and Dynamic Discharge board (GDDD) provides the interface isolation between the IGBTs and the main processor firing circuits. Dynamic discharge circuit control is implemented on the GDDD board as well as the gating circuits for the A leg and B leg active IGBTs.

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RTBA board determine if the LTB relays or external connections operate the RTBA relays. The eight LTB (or LUP) inputs are connected to the LDCC board via 8PL for use by the regulator controls.

2-5.7. RTBA (DS200RTBA)

The board also provides the instrumentation of the EX2000 PWM. Output dc voltage, dc link voltage, shunt current mv input, and the heat sink thermistor input are processed on the GDDD board and sent to the LDCC processors for use by the regulators.

The Relay Terminal Board (RTBA) board contains seven form C, DPDT relays that can be software driven via the LTB pilot relays or externally driven. The relay contact outputs are used for external customer interface. Each relay contains an LED that indicates when the relay is energized.

2-5.4. PTCT (DS200PTCT)

2-5.8. ACNA (DS200ACNA)

The Potential Transformer Current Transformer (PTCT) board isolates and scales the voltage and current signals from the PTs and CTs. It also provides auxiliary inputs and outputs for either low voltage (± 10 V dc) or 4-20 ma current signals. Secondaries of the isolation transformers are passed to the TCCB board via the JKK ribbon connector.

The ARCNET Board (ACNA) serves as the connection for the ARCNET data link for the EX2000 PWM regulator. Termination is made using co-axial cable. Each ACNA can terminate two co-axial cables. The Status S data link connection to the turbine controller is made on the ACNA board.

2-5.5. NTB/3TB (531X305NTB) 2-6. INPUTS AND OUTPUTS The NTB/3TB serves as a general purpose terminal connection board. Connections are made as an interface between the control core and other devices. The EX2000 PWM RS-232C serial port is located on this board. When supplied, the field ground detection inputs from the ground detector receiver are connected to the auxiliary VCO inputs on the NTB/3TB board.

The EX2000 PWM regulator has a limited amount of hard inputs and outputs that can be supported. For most applications, these will be conducted over the Status S data link. As a minimum, the following must be supported in the basic brushless regulator for basic/OEM offerings.

2-5.6. LTB (531X307LTB)

2-6.1. Generator Inputs

The LAN Terminal Board (LTB) is an I/O termination board that serves as an interface between the control core and other devices. Ribbon cable RPL allows software variables pointed to the seven low voltage, low current, form C LTB output relays to control higher voltage, higher current, form C RTBA board relays. Jumper settings on the

2-6.1.1. POTENTIAL TRANSFORMER INPUTS. Up to three sets of three phase PT inputs are supported. These inputs are a nominal 120 V secondary with software adjustments available for other nominal secondary voltages. The inputs are less than a 10 VA burden on the PT inputs. The first two PT sets are used to supply generator line voltage feedback information to the automatic (ac) regulator for control of the generator output

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voltage. The first PT set is used for generator control. The second set is used for PT failure detection and can be configured for control should the first set fail. These inputs also supply speed / frequency feedback information for the regulators, limiters, and protection functions, including the optional Power System Stabilizer (PSS). The third set of three phase PT inputs provides line side voltage and is used by the control for an optional voltage matching feature. These connections are made directly to the PTCT board.


2-6.3. Generator Line Breaker Status One form A contact input from the generator output circuit breaker is used by control, limiter, and protection functions. This contact is connected to an LTB input. The contact may be powered using the 70 V dc supply from the PSCD board.

2-6.4. Generator Lock-Out Trip One form A (closed when reset) contact input from a customer trip relay (86G typically) is supported for an external trip of the excitation control system. This contact must be powered from the 70 V dc power supply on the PSCD board.

Optional PT isolation switches for all three sets of inputs may be supplied.

2-6.5. Additional I/O 2-6.1.2. CURRENT TRANSFORMER INPUTS. One set of two phase CT inputs is supported. Phase A and phase C currents are required by the EX2000 PWM regulator. These CTs supply generator line current feedback information for use by regulator, limiters, and metering functions in the brushless regulator control, including the optional Power System Stabilizer (PSS). The inputs require a nominal 5 A secondary CT input. Software adjustments are available down to a nominal 3 A secondary input. The CT burden is less than 1 VA per phase. These connections are made directly to the PTCT board. Optional CT isolation shorting switches for each phase input may be supplied.

In addition to the I/O listed above, the following minimum inputs and outputs are supported. Not all applications will require each of the contact I/O or 4-20 ma inputs or outputs listed. Refer to the job specific elementary for those supplied. Input Regulator On / Off (Closed = Regulator On) This is used to start and stop the brushless regulator. Input Regulator Selector AC/DC (Closed = AC ) This is used to select the controlling regulator, auto (AC) or manual (DC). Input Regulator Raise (Close = Raise) This interfaces to the active regulator’s reference adjuster, ac or dc, and raises the setpoint.

2-6.2. 4 - 20 MA Inputs Optionally, the EX2000 PWM regulator can support two 4 to 20 milli-amp inputs for signals used to modify the overexcitation limiter / protection based on the cooling of the generator. On air cooled generators this input will be proportional to the cooling air temperature for the generator. On hydrogen cooled generators this input will be based on hydrogen pressure of the generator.

Input Regulator Lower (Close = Lower) This interfaces to the active regulator’s reference adjuster, ac or dc, and lowers the setpoint. Input PSS Enable/Off (Closed = Enable) This contact allows the PSS control to operate if minimum load permissives are reached. Input Status of Control Output Contactor This contact is used to monitor the status of the MDA contactor .


Output Exciter Alarm (30EX) This output provides a global exciter trouble alarm for customer annunciation Output Protective Transfer to dc Regulator / Transfer Regulator alarm (60EX) This contact provides an indication of an automatic transfer to manual regulator Output Regulator On This contact provides an indication that the EX2000 PWM regulator is operating. Output Exciter Trip Request (94EX) This contact output is a request from the EX2000 PWM to immediately trip the generator. Usually directed to the 86G device. Output Exciter Field Ground Alarm/Trip (64FA or 64FT) This contact output can be either an alarm or trip contact depending on customer preference.

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The voltage inputs supported are: Input from Exciter Field Ground Detector Alarm (+ 24 V) Input from Exciter Field Ground Detector Malfunction (+24 V) Input from Exciter Field Ground Detector Diode Fault (+24 volts) Up to four 4 to 20 milli-amp outputs are also supported. These outputs are provided through the digital to analog converters on the NTB/3TB board. They are software configurable. Typical uses are regulator output voltage, regulator output current, and regulator balance.

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Note: Not Certified for Construction. Figure 2-2. Mechanical Layout


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Figure 2-3. Front View

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Figure 2-4. Front View (Door Removed)


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Figure 2-5. Bridge Components

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Figure 2-6. Bridge Components (Isometric)


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TO TURBINE CONTROL OPERATOR INTERFACE METER DRIVER OUTPUTS QTY (4)

MAIN PROCESSOR BOARD

LDCC

MICROPROCESSOR APPLICATION BOARD

TCCB

POWER SUPPLY AND CONTACTOR DRIVER BOARD PSCD

GATE DRIVER AND DYNAMIC DISCHARGE BOARD

GDDD

PTCT BOARD ARCNET BOARD AC INPUT

ACNA

POWER CONVERTER MODULE (IGBT) DC INPUT 3 PHASE VOLTAGE SENSING INPUT

2 PHASE CURRENT SENSING INPUT DC OUTPUT TO EXCITER FIELD

LTB

CONTACT INPUTS/OUTPUTS

RTBA

CONTACT OUTPUTS

NTB/3TB

CONTACT INPUTS

WORK STATION

Figure 2-7. Typical Connection Diagram

RS232 PORT

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Notes:


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CHAPTER 3 SOFTWARE SYSTEM OVERVIEW

3-1. INTRODUCTION The EX2000 PWM regulator uses microprocessor based software that includes adjustable parameters. These parameters perform many functions once controlled through adjustable hardware and software combinations. The parameters are modified to customize the regulator to the specific hardware and application. They also enable field and maintenance personnel to fine tune the regulator for optimal performance.

personnel to troubleshoot, fine-tune, and maintain the installed EX2000 PWM regulator. Optional tool based modules provide real display of control variables and communications data. Publication GEH-5860 provides instructional information about DOS ST2000. Publication GEH6333 provides information about the Windowsbased Toolbox. These publications also include the PC requirements for running the tools.

3-3. PROGRAMMER MODULE Either the DOS-based ST2000 Toolkit or Windowsbased Toolbox and the LDCC board Programmer are used for making these software adjustments. These products are available as options from GE Motors & Industrial Systems for use by the customer. The programmer is provided with each unit.

3-2. CONFIGURATION TOOLS DOS based ST2000 and Windows-based GE Control System Toolbox are software toolkits used to configure, maintain, and fine tune the EX2000 PWM regulator. They consist of a collection of programs (tools) running under a command shell on an IBM PC-compatible computer.

The EX2000 PWM regulator includes a Programmer module with a 16 character digital display and an alphanumeric keypad. It functions as an operator interface for software adjustments and diagnostic testing when the ST2000 Toolkit is not available.

NOTE Permanent changes made using the Programmer module must also be made in the configuration tools to keep them up to date with the exciter’s software configuration. Contact GE Motors & Industrial Systems for support in this area.

3-3.1. Using The Programmer The toolkit includes an extensive database of EX2000 definitions, accessed and manipulated using menu driven selections. Additionally, the ST2000 program can graphically display the exciter’s program logic on the computer screen. By viewing the logic flow, the user can better understand and manipulate the exciter’s adjustable values. ST2000 is used at the factory to initially configure and test the systems. At the customer site, the tools enable GE field engineers and other trained

Publication GEI-100242 provides information on how to operate the Programmer module.

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3-3.2. Software Design The exciter application program consists of functional software modules (building blocks) combined to perform to system requirements. Block definitions and configuration parameters are stored in read-only memory (ROM), while variables are stored in random-access memory (RAM). Microcontrollers execute the code. The exciter application software emulates traditional analog controls. The software uses an open architecture system, which uses a library of existing software blocks. The blocks individually perform specific functions, such as logical AND gates, proportional integral (PI) regulators, function generators, and signal level detectors. These blocks are tied together in a pattern to implement complex control systems. For example, a control function such as the under-excitation limit (UEL) is included as an ac regulator input by setting software jumpers in EEPROM. The relevant blockware is enabled by pointing the block inputs to RAM locations where the inputs reside (the UEL requires megawatts, kilovolts and megavars). The UEL output is then pointed to an input of the ac regulator summing junction. The software blocks are sequentially implemented by the block interpreter in an order and execution rate defined in ST2000. The blockware can be interrogated while running by using ST2000. The dynamically changing I/O of each block can be observed in operation. This technique is similar to tracing an analog signal by using a voltmeter.


3-4.1. Automatic Voltage Regulator (AVR) Ramp The AVR ramp block accepts an input from the operator via the Status-S page for auto re gulator raise or lower. The reference then ramps at a predetermined rate, within an upper and lower limit (usually 0.9 to 1.1 pu terminal V). The output can be preset to a value upon startup. Automatic tracking of the AVR track value is performed when operating in manual regulator. Refer to Figure 3-2.

3-4.2. Automatic Voltage Regulator Setpoint The AVR setpoint block sums the output from the reactive current compensation (RCC), AVR ramp, UEL output, and power system stabilizer (PSS) output. This sum is compared to the V/Hz reference in a minimum select block and then passed through a high limiter as the AVR output signal. By selecting a negative or positive gain, line-drop or droop compensation mode may be selected on the RCC. An auto/manual command via the operator generates auto active or manual active status indicators. A PT failure can also select manual. Refer to Figure 3-3.

3-4.3. Automatic Voltage Regulator The AVR block combines the AVR setpoint with the negative generator terminal volts to provide an error signal. This is passed through to the automatic regulator proportional and integral gain sub-blocks, and then passes through the auto regulator limits to the manual voltage regulator. The auto regulator is modeled by the following transfer function:

3-4. STANDARD FUNCTIONS AVR out = AVR error (Kp + KI)/S. See Figure 3-4. Table 3-1 is a description of the inputs and outputs for the more significant blocks used in the EX2000. These inputs and outputs can be monitored through ST2000, if desired. Also, the significant adjustments of those functional blocks are described as Adjustable Constants. These constants represent limits, gains, and setpoints. They are functionally equivalent to potentiometers or other discrete adjustment devices used in previous excitation systems.

3-4.4. Field Regulator (FVR) Ramp The FVR ramp block accepts an input from the operator via the Status S page for manual regulator raise or lower. The reference then ramps at a predetermined rate within an upper and lower limit


(usually 0.7 pu VFNL to 1.2 pu VFFL). The output can be preset to a value upon startup. When in auto regulator mode, the FVR ramp tracks the value of IFE, exciter field current. Refer to Figure 3-5.

3-4.5. Field Regulator The exciter field regulator is configured as a current regulator in the EX2000 PWM. The reference input to the FVR is from either the manual regulator ramp block or the AVR. When fed from the AVR, the field regulator is used as an inner loop. A bridge firing enabled signal is also provided to keep the exciter turned off until bridge firing has been enabled. Refer to Figure 3-6.

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3-4.7. Over Excitation Limiter (OEL) In the EX2000 PWM, the alternate current regulator is initially enabled. If the signal level detect looking at exciter field current or either of the inverse time protection blocks activate, the alternate field current regulator is disabled and the primary current regulator setpoints are active. The output of either the alternate or primary field current regulator is fed to the firing block where a minimum select with the field regulator firing command is performed. A cool down function is also supplied to simulate cooling of the field after an overexcitation condition. Refer to Figure 3-8.

3-4.8. Firing Block 3-4.6. Under Excitation Limiter (UEL) The UEL blocks accept watts and volts as inputs and calculates a VAR reference. Using a table lookup which approximates the underexcited capability of the generator, the VAR reference is then compared to the actual unit VARs to develop a VAR error signal. The error signal is then passed through a proportional and integral regulator sub-block to keep the machine within its underexcited capability. Refer to Figure 3-7.

The firing block accepts the field current reference and the field voltage reference and then selects the least of the two. This signal is passed on to the bridge only if the instantaneous overcurrent or the stop commands are not activated. If either of these are active, the firing signal is a preset retard limit. Refer to Figure 3-9.

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Table 3-1. Standard Software Functions Function

Inputs

Adjustable Constants

Outputs

AVR Ramp

Auto Increase (RF1@IN) Auto Decrease (RF1@DC) Manual Active (RF1@VE) Go to Preset (RF1@3E) Track Enable(RF1@T2) Track Value(RF1@2E)

High limit (RF1THO) Low limit (FR1TLO) Ramp rate (RF1NRT) Preset value (RF1@T3) Track lag (RF1WLG)

Reference out

AVR Setpoint

Frequency (ASP@FQ) React. Cur.(ASP@IQ) REF Out (ASP@RO) UEL Out (ASP@UE) PSS Out (ASP@PV) Auto/Man (ASP@AC) Extra Input (ASP@EX) PT Fail (ASP@PT) Gen Volts (ASP@VM) PSS Armed (ASP@PC) Gen Watts (ASP@WT) PT Fail Reset (ASP@PR)

ASP Limit High (ASPHLM) V/Hz Gain (ASPVHZ) RCC Gain (ASPRCC) PSS High Watt (ASPHIW) PSS Low Watts (ASPLOW)

AVR Ref Auto Active Man Active PSS Active V/Hz Active UEL Active Setpoint In Limit Latched PT Fail

FCR

FCR Setpoint FCR@SP FCR Enable FCR@EN FCR Alternate Setpoint FCA@SP FCR Alternate Enable EFA@EN

FCR Prop Gain (RGKC0) FCR Integral Gain (IRWIC0) Alt FCR Prop Gain (IRGKA0) Alt FCR Integral Gain (IRWIA0)

FCR Output ILOP0

AVR

Generator Volts (AVR@FB) FVR Output (AVR@TV) AVR Ref (AVR@SP) Manual Active (AVR@TC) Bridge Fire Enabled (AVR@ZC)

High Limit (AVRPLM) Low Limit (AVRNLM) Prop. Gain (AVRPGN) Integral Gain (AVRIGN) Tracking Gain (AVRTGN)

AVR Out AVR In Limit AVR Error

FVR Ramp

Manual Increase (SS) Manual Decrease (SS) Auto Active (RF2@2E) Go To Preset (RF2@3E)

High limit (RF2TH0) Low limit (RF2THL) Ramp rate (RF2NRT) Preset value (RF2@T3)

Reference Out

FVR

Field Current (IFE) AVR Out (EFR@TV) FVR Ref (EFR@SP) Auto Active (EFR@EN) Bridge Fire Enabled (MPWRENAB)

FVR Turn Off (FLDZVL) Tracking Gain (FLDTGO) Proportional Gain (FLDPGO) Integral Gain (FLDIGO)

FVR Out


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Table 3-1. Standard Software Functions - Continued Function

Inputs

Adjustable Constants

Outputs

UEL

Watts (RA1@I1) Gen. Volts(@INPUT) VARs (R2@FBO)

VARs Ref. 0 (FGENYO) Watts Ref. 1 (FGENX1) VARs Ref. 1 (FGENY1) Watts Ref. 2 (FGENX2) VARs Ref. 2 (FGENY2) Watts Ref. 3 (FGENX3) VARs Ref. 3 (FGENY3) Watts Ref. 4 (FGENX4) VARs Ref. 4 (FGENY4) Prop. Gain KP (R2KFBO) Integral Gain KI (R2WI_0) High Limit (R2LMPO) Low Limit (R2LMNO)

UEL Output

OEL

Field Current (CURRENT)

High Limit (CRLMHI) 2 Low Limit (I tAFL) FCR Preset (PIT@RS) Inst. Overcur. Lim (PITPU) IIT Limit (PITLM) FCR Pos. Limit (FCRPLM) 2 IIT Cooling Mult. (I tCMT)

OEL Act (FLDMOD) IIT Acc (PITIACCM)

Firing Block

FVR Out FCR Out IOC Active Start/Stop

Retard Limit

Firing Code

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Figure 3-1. Software Overview


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Figure 3-2. Automatic Voltage Regulator (AVR) Ramp

Figure 3-3. Automatic Voltage Regulator (AVR) Setpoint

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Figure 3-4. Automatic Voltage Regulator (AVR)

Figure 3-5. Field Voltage Reg (FVR) Ramp


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Figure 3-6. Field Regulator (FVR)

Figure 3-7. Under-Excitation Limit (UEL)

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Figure 3-8. Over Excitation Limit (OEL)


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Figure 3-9. Firing Block

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Notes:


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CHAPTER 4 SOFTWARE CONFIGURATION AND SCALING

4-1. INTRODUCTION The software to configure various regulators, metering, and protective functions within the EX2000 PWM regulator operates on a count system representing actual feedback values. These feedbacks are generated by current transformers, voltage transformers, and dc shunts. The signals may pass through isolators and amplifiers. These analog signals are transformed to digital signals by means of voltage controlled oscillators. The regulator controls use standard normalized values to represent the variable being monitored or regulated. This enables the use of software that, to a large extent, is not application dependent. For example, the automatic voltage regulator (AVR) controls the generator terminal voltage based on a setpoint chosen by the operator. For any machine, 1 per unit (or rated terminal voltage) is defined within the AVR to be 20000 counts. If the operator chooses to set the terminal voltage at rated then the reference to the AVR is 20000 counts. The voltage feedback counts are compared to this reference to generate an error signal and the appropriate control action takes place to maintain the feedback counts at 20000. The actual generator terminal voltage being regulated is not referenced at this control level. It is therefore necessary to ensure that the feedback counts seen by the regulators are adjusted to provide the standard number of counts when the generator is operating at rated. This is referred to as scaling. An EX2000 system can be constructed several ways to accommodate customer system requirements. For example, the regulator can be fed from the permanent magnet generator or from an auxiliary bus. It can be a brushless regulator or an SCT control winding regulator. The controls are set to match the hardware used. This is known as configuration.

4-2. CONFIGURATION AND SCALING EXAMPLE The following section shows how scaling is performed using example generator data. The example system is configured as a Brushless exciter regulator fed from a PMG with a 125 V dc battery backup. There is also a single set of generator potential transformers (PT)s and no line PTs. The scaling may not apply to all EX2000 applications. Contact GE Motors and Industrial Systems before changing any EE Values. Even though the EX2000 PWM is a brushless regulator and as such, operating data from the generator field is not readily available to the regulator, the generator information listed is critical to the overall operation and performance of the regulator and excitation system. Assumptions made in the AVR and exciter field regulators are based upon the available generator data.

4-2.1. Example Generator, Exciter And Regulator The example generator, exciter, and regulator data in this chapter is as follows:

4-2.1.1. GENERATOR DATA: KVA 100000 Frequency 60 Hz Volts 13800 PF 0.85 Cold Gas Temperature 40 °C Rated Stator Amps 4184 Amps Field No Load 313 Amps Field Air Gap 281 Amps Field Full Load 846 Amps Field Ceiling 1360 Field Open Circuit Time Constant (T’do) 5.615 sec Field Open Circuit Subtransient (T’’do) 0.022 sec

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Field Winding Resistance 0.199 ohms at 25 °C Volts Field Full Load 136 Station battery volts 125 V dc PT Ratio 14400/120 Current Transformer (CT) Ratio 8000/5

applications and should not be changed or need changing on any requisition. If any parameters not discussed in this manual are in question, contact the product service group of GE Motors and Industrial Systems or the local GE service organization for advice.

4-2.1.2. EXCITER DATA: kW Volts Rated Exciter Output Amps Amps Field Air Gap (exciter) Amps Field No Load (exciter) Amps Field S ynch Imp.(exciter) Amps Field Full Load (exciter) Amps Field Ceiling (exciter) Exciter Time Constant (T’do) Field Winding Resistance (exciter)

268 300 893 1.712 3.52 6.236 9.54 15.45 0.35 sec 4.871 ohms at 25 °C

Generator Model Jumper EE.3850 (GMJMPR)

EE.3850.1

EE.3850.2

EE.3850.3

4-2.1.3. REGULATOR DATA: DC shunt Dynamic Discharge Resistor Dynamic Discharge Resistor Rated Amps Charge Control Resistor Voltage Doubling DC Link Expected Volts from PMG Maximum Expected DC Link Volts

The following are general configuration adjustable parameters (EEPROM) used to direct signals and help make the configurable blockware function as a brushless regulator.

10 A = 100 mv 17.0 ohms 6.0 A 2.0 ohms No 137

EE.3850.4

EE.3850.5

EE.3850.6

360 EE.3850.7

4-3. GENERAL CONFIGURATION Throughout this example, the software nomenclature is defined as follows:

EE.3850.8

EE.XXXX (ABCDEF), where "XXXX" represents the software address location and "ABCDEF" represents the software address name.

EE.3850.9

There are many parameters that are set in the EX2000 PWM which are not discussed in this manual. Many of them are used to set up configurable parameters such as the Status S data link, communication, and so on. These are fixed parameters baud rates, displays configuration, keypad configuration for all EX2000 PWM

EE.3850.10

Used to simulate PT failure in simulator mode. Normally set to zero. Selects slip source for Power System Stabilizer (PSS) The example has no PSS Selects extra PT source for calculation of PT failure. Can only be from PTCT board for EX2000 PWM. Set to (0). Generator model type. Can be static (0) or rotating (1). Brushless regulator is rotating. Selects 50 hz (1) or 60 hz (0) system for simulator and normal operation. Example is 60 hz. Selects terminal (0) or separately fed (1)inputs for bridge. EX2000 PWM is separately fed. Selects whether the extra PT is used for calculations if a PT failure is detected. (1) is yes, (0) is no. No PT failure detection available in the example. Selects location of extra PT input. Line side (1) of 52G breaker or generator side (0). Example does not have extra PT input. Select if PT failure detection is always (0) or only with 52G closed (1). No PT fail detection in example system. Set to zero. Use maximum of PT feedbacks for calculations. (1) is yes, (0) is no. No for example.


EE.3850.11 EE.3850.12

EE.3850.13

Adjusts simulator for 60 hz (0) or 50 hz (1) Sets LOE calculation for high gain (rev. G1B) PTCT board for LOE calculations. All new EX2000 PWM use high gain PTCT inputs. Set to (1) Adjusts PTCT board inputs for Rev. A (0) or Rev. B (1) board.

Configuration Jumper EE.589 (ECNFIG) EE.589.0

EE.589.2

EE.589.4

EE.589.6

EE.589.8

EE.589.10

Selects IFG feedback to be from SHPL on GDDD (1), IA2PL from GDDD (2) or none (0). Set to 2 for EX2000 PWM Selects IFE feedback to be from SHPL on GDDD (1), IA2PL from GDDD (2) or none (0). Set to 1 for EX2000 PWM Selects VFG to be from APL/BPL on GDDD board (1), IA1PL on GDDD board (2) or none (0). Set to zero for EX2000 PWM. Selects VFE to be from APL/BPL on GDDD board (1), IA1PL on GDDD board (2) or none (0). Set to one for EX2000 PWM. Selects field regulator feedback to be either VFG (0), VFE (1), IFG (2) or IFE (3). EX2000 is a current regulator for the exciter field. Set to three. Selects source for Var.105 to be either IFG (0) or IFE (1). Set to 1 for EX2000 PWM.

Other general configuration parameters important to the operation of an EX2000 PWM regulator EE.550 EE.556

Identifies product type. For EX2000 hardware select 4. Identifies hardware feedback board. For EX2000 PWM select GDDD board 2.

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4-4. FEEDBACK SCALING As a brushless regulator, there are a limited number of feed back signals from the generator available to the EX2000 PWM. These are potential transformers and current transformers monitoring the stator output, a shunt feed back from the exciter field, and exciter field voltage. Main generator field current and voltage are not commonly available for display or control on a brushless generator. The following sections will detail the common feed back signals and the scaling used in the EX2000 PWM.

4-4.1. Generator Feedback The PT and CT signals to the EX2000 PWM regulator are isolated by the PTCT board. The voltage signals generated by the PTCT are sent to the TCCB transducer board. Here voltage controlled oscillators (VCO) translate the analog signals into digital counts. The PTCT board will accept one set of three phase CT inputs from the main generator stator current transformers. These CT’s must have a nominal 5 amp secondary and phase A and C are required for correct operation of the EX2000 PWM regulators. Phase B CT input is not required and is not used by the controls. EE.3840 CT_ADJ is used to account for off nominal CTs. The scaling for this EE setting is calculated as equal to 20480/(actual 1 pu CT secondary amps) For the example generator data: EE.3840 = 20480/(4184*5/8000) = 7832 The PTCT board also accepts up to three sets of generator voltage transformer inputs. These inputs are three phase inputs with a nominal secondary voltage of 120 V ac. Two of the inputs are for generator voltage before the synchronizing breaker. These two PT inputs should both be on the same side of the generator step up transformer. The third input can be used for a line side of the synchronizing breaker voltage input. The scaling for this EE setting is calculated as equal to 491520/(actual 1 pu PT secondary volts)

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For the example generator data: EE.3841 = 491520/(13800*120/14400) = 4274

4-4.1.1. POTENTIAL TRANSFORMER FAILURE DETECTOR (PFTD) OPERATION. In the example system only one set of PT inputs are specified. The second set of generator side PT’s can be used for an optional Potential Transformer Failure Detection (PTFD) function. The generator PTFD operates by comparing the sum of the absolute counts for V12 and V23 signals (generator PT signals) with the sum of the absolute counts representing the extra PT input signals VX12 and VX23. The 1 pu secondary voltages from these two sources depends on the transformer ratios used. A scale factor PTFDSC EE.3835 is used to null the signal difference that could exist. The resulting magnitude difference is filtered and the absolute value is compared to the failure detection level set by EE.3837 PTFDVL. Under normal conditions the difference between the two sums should be approximately zero. If this absolute difference is greater than the value set by PTFDVL EE.3837 then a PT FAIL FLT.488 is generated and VAR.1166 EXPTFD becomes true. This variable is sent to the excitation autosetpoint block input ASP@PT and, if true, forces a latched transfer to the manual regulator. The PTFD can be disabled off-line by setting EE.3850.9 GMJMPR.9 equal to 1. The PTFD detector can be tested using the simulator by setting GMJMPR.1 equal to 1 to simulate loss of V12 PT signal.


4-4.1.3. PTFD DETECTION LEVEL. The failure detection level is set using PTFDVL EE.3837. It is typically set to approximately 50% of nominal (120 V) PT signal (loss of half the voltage of one phase). For the example system, EE.3837 = 0.5 * 2048 * (115/120) = 981. In the formula, 2048 represents a complete loss of a PT signal and 115 is the actual 1 pu PT secondary volts. A PT failure detection causes automatic transfer to the field (or manual) regulator. This regulator controls field current level and does not look at generator terminal voltage. This is the only fault that initiates automatic transfer to the manual regulator. It is not possible to transfer back to the AVR until this latching fault is cleared. The operator interface should indicate when a PTFD has occurred. A reset signal must be sent to reset the PTFD. A soft reset of the core is necessary to clear the fault display from the LDCC board once the PT feedback problem is fixed.

4-4.1.4. P.T.U.V. If a second set of generator PT’s is not provided then the PTFD scheme described above can not be used. In this case the PTFD function is disabled by setting EE.3837 to 65,535 and protection is provided by pointing ASP@PT at VAR.1182 EXPTUV. In the event of loss of one phase or complete loss of generator voltage signal as measured by the TCCB board, and after a time delay specified in EE.3834 PTFDT1. EXPTUV will become true, forcing the control into manual regulator mode.

4-4.2. Bridge Voltage Feedback Setting EE.3850.9 GMJMPR.7 equal to 1, the extra set of PTs can be used for all calculations downstream from the PT failure detector software.

4-4.1.2. PTFD SCALING. Parameter PTFDSC EE.3835, PT failure scale adjust, is used to null any signal difference existing between V and X PTs. If a second PT for failure detection were supplied, then set EE.3835 = 4096 * (1 pu V PT secondary volts/1 pu X PT secondary volts). In most cases, the second set of PT inputs would be the same secondary as the first and the default value of 4096 would be used

The bridge (regulator) dc output voltage feedback signal is fed via APL-5 and BPL-6 f rom the IAXS board to the GDDD board. A voltage controlled oscillator on the GDDD board converts this analog


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signal to a frequency and digital counts. JP1 on the GDDD board is set per the maximum expected dc link voltage. For units not employing the voltage doubling feature of the EX2000 PWM regulator, this is normally 360 volts. The example system does not use voltage doubling.

EE.1508 VF1OF0 is used to zero the VFB1 bridge voltage feedback offset. With no bridge output, variable 1014 should be read using diagnostic test 31. This count value multiplied by the constant 1141 and divided by the scale factor value in EE.612 VDCMAX then becomes the value in EE.1508.

The dc link voltage feedback signal is fed to the GDDD board via the DCPL -1 and 2 connections on the IAXS board. Again, JP2 on the GDDD board is set to the maximum expected DC link voltage.

For example, with power on the bridge but the bridge not firing, monitor VAR.1014 (assuming VFE is the selected feedback) for any zero offset. Assume the offset found was approximately 80 counts. Set EE.1508 = (80*-1141)/360 = -253. Enter this value and continue to monitor VAR.1014 to verify that the offset is now zero.

EE.612 VDCMAX sets the 1 pu count level (20000) equal to 360 or 604 volts for scaling of both the DC link voltage and DC output voltage. JP3 on the GDDD board sets the operation level of the dynamic discharge firing circuit. The selection of JP3 is also based upon the maximum expected dc link voltage. JP1, 2 and 3 on the GDDD board should all be set to the same settings.

EE.1510 CF1OF0 is used to zero the CFB1 bridge current feedback offset. With no bridge output, variable 1016 should be read using diagnostic test 31. This count value multiplied by the constant 21475 and divided by the scale factor value in EE.1505 CFS1F0 then becomes the value in EE.1510.

4-4.3. Bridge Current Feedback The EX2000 PWM regulator field current feedback signal is from shunt SHA and is fed to the GDDD board via connections SHPL-1 and -2. This input is scaled using EE.1505 CFISF0. This trims the gain of the VCO to achieve 5000 counts at 1 pu bridge current. The scaling for this EE setting is calculated as EE.1505 = 32768*(shunt rating)/(regulator amps field full load). For the sample system, the shunt rating = 10 A for 100 mv. The exciter AFFL rating is 9.54 A. Set EE.1505 = 32768 *(10)/(9.54) = 34348

4-4.4. Feedback Offsets Due to the tolerance limits of the op-amps and VCOs that provide the EX2000 PWM feedbacks, it is possible that positive or negative offsets may occur with zero signal feedback. The actual offsets produced are dependent on the actual hardware and must therefore be zeroed at startup. The bridge output voltage, dc link voltage and shunt feedback are adjustable using the following feedback offsets.

For example, with power on the bridge but the bridge not firing, monitor VAR.1016 (assuming IFE is the selected feedback) for any zero offset. Assume the offset found was approximately -100 counts. Set EE.1510 = (-100*21475)/34348 = -62 Enter this value and continue to monitor VAR.1014 to verify that the offset is now zero. EE.1513 VDCOF0 is used to zero the dc link voltage feedback offset. Since dc link voltage is required for control power, this offset must be made with dc link voltage present. VAR.1018 should be read using diagnostic test 31. The dc link voltage should be read on the IAXS board c onnection points PL and NL. This measured voltage will then be converted to counts. The converted measured counts minus the count value in VAR.1018 then becomes the value in EE.1513.

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For example, with power on the bridge but the bridge not firing, monitor VAR.1018. Assume it is 7825 counts. Then assume the measured value of the dc link is 137 volts. Converting the measured voltage to counts gives 137/360 * 20000 equals 7611. Set EE.1513 = (7611-7825) = -213 counts. Enter this value and continue to monitor VAR.1018 to verify that the offset is now zero.

4-4.5. Instantaneous Overcurrent Trip An instantaneous overcurrent trip occurs if the bridge current, as monitored by SHPL (CFB1), exceeds the threshold set by EE.1518 IOCTRO where 5000 counts = 1 pu Set EE.1518 = 25000 (5 pu) with EE.1517 IOCTDO = 0 for no time delay.

4-5. REGULATOR SCALING There are several regulators and limiters available in the EX2000 PWM. The applicable one-line or system ordering documents will detail whether or not all or any of these are supplied on a given requisition. Generally the AVR, FVR, and OEL regulators are supplied as standard. The UEL, RCC, and V/hz limiters are also generally standard features. PSS and VAR/PF controllers are typically supplied as options.

4-5.1. Automatic Voltage Regulating System The primary purpose of the automatic voltage regulator (AVR) is to control the generator terminal voltage according to a chosen reference. The terminal voltage can then be modified by various limiter and regulator functions.

4-5.1.1. AVR OPERATION. The EX2000 PWM is designed to be started in AVR. The exciter can be started in AVR mode with the generator operating from 20 to 100 Hz. To prevent initial overshoot, the integrator is held at the preset value until 95% voltage is obtained. For a normal bandwidth AVR, this also means forcing the regulator to its maximum output until 95% of terminal voltage is reached. If the speed of the generator is below rated when the regulator is started, the V/Hz limiter will hold down


the terminal voltage and regulator output such that the volts per hertz ratio specified in the AVR controls is maintained.

4-5.1.2. REF1 OPERATION. The selected (unmodified) reference originates in the INC/DEC reference block REF1 (see Figure 3-2). The initial reference used in the EX2000 PWM is a preset value normally set for 1 pu generator voltage. The REF1 output tracks this value when a start is given to the regulator. During this initial operation the RAISE and LOWER controls are ignored. Once the startup operation is complete, the reference can be changed by selecting RAISE or LOWER from the operator station with the regulator in AUTO regulator. When off-line, selecting RAISE or LOWER controls the generator terminal voltage over a range set in REF1 (and the autosetpoint block). This range is normally ±10% of rated terminal voltage. When on-line, selecting RAISE or LOWER increases or decreases the generator terminal reactive voltage and/or the power output of the generator. The more stiff the connection to the power system (lower impedance tie) the less the generator terminal voltage is able to change. An optional volt ampere reactive/power factor (VAR/PF) controller can also control the output of the REF1 block. While under control of the VAR/PF controller, the slew rate of REF1 is slowed to an alternate ramp rate, and the operator RAISE/LOWER inputs are ignored. When the exciter is operating in manual, the autosetpoint reference REF1 tracks a value representing the sum of ASP@VM (normally generator voltage) and the reactive current compensation signal. While REF1 is tracking this value, the INC/DEC commands from the operator station are ignored in the REF1 block. The output of REF1 in VAR.282 REF1OUT0 is passed to the autosetpoint block (EXASP).

4-5.1.3. REF1 SCALING AND CONFIGURATION. REF1 tracks target RF1@T3 EE.3402 without delay during startup. It is normally pointed to a value of 20000 counts for 1 pu generator voltage. For 1 pu generator voltage set EE.3402 = 19.


During startup, a quick store register can be used to preset the terminal voltage to a value other than rated. This register can contain a count value representing the desired preset voltage. RF1@T3 should then be pointed to this address. For example, during startup, if the desired preset voltage is 12.5 kV on a 13.8 kv machine, the reference preset counts required is 12.5/13.8 * 20000 = 18116 counts. Quickstore EE.95, currently an unused register, can be used to store this value. Then, point EE.3402 (RF1@T3) to EE.95 instead of the normal EE.19 location. The range of the AVR is set using EE.3414 RF1TH0 (upper limit) and EE.3412 RF1TL0 (lower limit). Set this to provide a range of ± 10% of rated generator voltage. Set EE.3414 = 18000 and EE.3412 = 22000. To select the ramp rate of the AVR set EE.3400.6 = 0 for a normal INC/DEC scale control setting of 1/10 bits/sec. The time to ramp across the AVR range is set by the normal INC/DEC rate EE.3421 RF1NRT. The range of the AVR = (22000-18000) = 4000. The desired time to cover this range is 60 seconds taking into account the setting of EE.3400.6. Set EE.3421 = (4000/60) *10 = 667.

4-5.1.4. AUTOSETPOINT BLOCK. The selected reference from REF1 enters the autosetpoint block (EXASP) as the main auto reference setpoint. This reference can now be modified in the autosetpoint block by various standard and optional regulators and limiters. In addition to the REF1 input the ASP block receives feedback variables for reactive current, generator terminal voltage, generator frequency, the output of the under excitation limiter, and generator real power if a power system stabilizer (PSS) is used (see Figure 3-3). Automatic regulation is enabled through the operator station or the A/M selector button on the LDCC board programmer keypad. When auto is active, VAR.953 ASPAUTOA will be true. The ASP block also has an input from the PTFD (or

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PTUV). When a PT failure is detected, regulation is switched to the MVR. ASPAUTOA becomes false and remains latched in that state until the PT feedback problem is corrected, the core is soft reset, and the PTFD reset button on the operator station is pushed to permit selection of AUTO operation. Configuration jumper EE.589 selections can disabled the PTFD while off-line. The ASP block contains a summing junction, minimum value gate, and a positive output limiter. The summing junction adds the output of REF1, the UEL regulator output, the PSS regulator output (if present), and an extra input ASP@EX. This extra input can be used to insert a test signal. The RCC compensation signal is subtracted in the summing junction. The output of the summing junction feeds a minimum value gate where it is compared with a V/Hz limit signal proportional to the generator frequency by an amount set in EE.3789 ASPVHZ. The minimum of these two references is used as the reference sent to the regulator. The maximum output is limited to a value set in EE.3790 ASPHLM. If the reference used by the regulator is the V/Hz limit and the exciter is in auto, then VAR.958 ASPVHZA is set true and an indication is given that the exciter is in V/Hz limit. If a positive value is input to the summing junction from the UEL and the exciter is in auto, then VAR.959 ASPUELA is set true and an indication is given that the exciter is in UEL. The output of the AVR setpoint block VAR.158 ASPAVRSP is sent to the AVR block as the regulator reference signal.

4-5.1.5. AUTOSETPOINT BLOCK SCALING AND CONFIGURATION. For the example system the V/Hz limiter will be set to 110%. Set EE.3789, the V/Hz gain, to 282 (256 = unity) For 50 Hz applications, multiply EE.3789 by 6/5. The ASP High Limit is set in EE.3790 ASPHLM. This is generally set for 110% of rated or 22000 counts. For 50 Hz applications, multiply EE.3790 by 6/5.

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4-5.1.6. AUTOMATIC VOLTAGE REGULATOR (AVR) BLOCK. The AVR is a

4-5.1.7. AVR SCALING SCALING AND CONFIGURATION. The AVR response is not set

proportional plus integral regulator that compares the generator terminal voltage feedback (derived from the V12 and V23 generator PT signals) with a reference from the auto auto setpoint block to produce an error signal. signal. This error signal, VAR.156 AVRERROR, is fed to the PI regulator. If the EX2000 PWM is in automatic regulator, the output of the AVR, AVROP VAR.157 is then fed to the inner loop field field regulator. The AVR output output is limited to approximately 2 pu field current so as to not overdrive the exciter. The output of the AVR is passed through the field regulator to cancel the impact of the additional time constant of the rotating exciter. By doing this, this, the calculations calculations and settings settings of the various regulator limiters, (UEL, V/Hz, OEL) can be set using the same rules as a terminal fed or bus fed excitation excitation system. Tuning of regulators regulators in the field is thus minimized.

for optimum speed, but for acceptable performance without risking instability due to local mode oscillations. This setting is considered to be a normal bandwidth regulator. A high bandwidth high bandwidth regulator is used when a high gain fast response AVR is required. The example assumes assumes a normal bandwidth regulator. If a high bandwidth regulator regulator is chosen, then the high bandwidth settings for the UEL regulator should be used also.

The AVR is preconditioned to a value corresponding to AFNL at startup. startup. The initial value of AFNL used could be an estimated value. After the initial startup, when a precise value of firing command counts for AFNL is known, the preconditioning value stored in EE.92 can be adjusted accordingly. When the precondition input AVR@ZC is true, the AVR output follows the preconditioning value AVR@ZV. If AVRJMP.0 = 1 the the integrator continues to follow AVR@ZC until AVRERROR is less than 5% (1000 counts on a 20000 base). If, in addition to AVRJMP.0 = 1, AVRJMP.1 also = 1 then the output of the AVR is forced to maximum as set in EE.3772 AVRPLM until the AVRERROR is less than 1000 counts. counts. If the exciter is in MANUAL (ASPMANUA true), the AVR tracks the output of the field regulator FLOPO VAR.1004. The AVR integrator has anti-windup protection that zeros the error feeding the integral gain if either: a.

The ou output is is in in po positive li limit or or if if th the and the EX2000 PWM regulator is in FCR and the error signal feeding the regulator is positive.

b.

The AVR output is in negative limit or in or in full retard and the and the error signal feeding the regulator is negative.

EE.3759.0 is set to 1 for AVR output to AVRJMP EE.3759.0 is follow AVR@ZC until regulator error is less than 1000 counts. Set at 1 for a high bandwidth exciter also. EE.3759.1 is EE.3759.1 is set to 1 on a normal bandwidth exciter to hold AVROP in ceiling until AVRERROR is less than 1000 counts. Set to zero for a high bandwidth exciter. AVRPLM EE.3772 is the positive limit for AVR 10000, which is output. Normally set to 10000, approximately 2 pu current for the exciter field. AVRNLM EE.3773 is EE.3773 is the negative limit for AVR output. Set to 0 AVRTGN EE.3770 is EE.3770 is the AVR tracking gain. This sets the time delay for the AVR to track the output of the field regulator while in manual regulator. Set EE.3770 = 5 (where 100 = 1 rad/sec) for a 20 second tracking filter. The following is an example of setting the AVR regulator for an EX2000 PWM regulator with normal bandwidth. Prior to startup, the AVR output is preset to the no load exciter field current level. This effectively wipes out overshoot problems when starting in the automatic regulator.


AVR@ZV EE.3764 points EE.3764 points to EE.92 In EE.92, the RUN2RF storage register stores the firing command count value necessary to produce 80% exciter AFNL. In the example, exciter AFNL was 3.52 A dc.

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4-5.1.9. INTEGRAL GAIN. Set Kp/Ki = 1 for a lead time constant constant of 1 sec. For the example example Ki = Kp = 1.67 Set AVRIGN EE.3771 = 1.67 * 100 (where 100 = 1 rad/sec) = 167

Set RUN2RF EE.92 to EE.92 to a FIRCMD = 0.8 * AFNL* 5000/AFFL = 0.8*3.52*5000/9.54 = 1476

4-5.2. Under Excitation Excitation Limiter Limiter (UEL) 4-5.1.8. AVR PROPORTIONAL PROPORTIONAL GAIN. The proportional gain of the PI regulator is set as follows: 1.

Determ Determine ine the transi transient ent gain gain requ require iremen ments ts of the system.

2. Calc Calcul ulat atee the the prop propor orti tion onal al gai gain n whic which h is directly proportional proportional to the transient gain. For the normal bandwidth regulator, set the transient gain to 4*T’do (the open circuit field time constant) with 20 as a default minimum for new gas and steam applications. A high bandwidth regulator should be set for a transient gain of 100. From the transfer function of a brushless EX2000 PWM regulator, the relationship between proportional and transient gains is: Transient gain = (Kp*20000 * K ex*AFFLex) / (VFAGgen*5000) where Kex is the gain of the exciter. The gain of the exciter exciter is calculated as the (voltage out/current in) or ((VFFLgen at 100 C VFNLgen at 100 C) / (AFFLex - AFNLex)). For the example system, K ex is calculated to be (21680.13)/(9.54-3.52) = 22.51. VFAGgen is the air gap voltage which is determined by reading IFAG from the machine estimated air gap line at 1 pu pu armature voltage. voltage. The example generator has IFAG of 281 A dc. The rated field resistance Rf@rated temp is defined as 100 C. The Rf@100C was not given and is therefore extrapolated from Rf@125C to give Rf@100C = .256 ohms. VFAG = .256 * 281 = 72 V dc. Solving for Kp gives Kp = (transient gain * VFAGgen*5000) / (20000 * K ex*AFFLex) = (20*72*5000) / (20000*22.51*9.54) = 1.67. Set AVRPGN EE.3769 = EE.3769 = 1.67 * 256 (where 256 = unity) = 429

The two basic problems with operating a generator in the underexcited region of the capability curve are stator end iron heating and generator steady state stability limit. Stray flux in the end end turn region of a high speed steam or gas turbine driven generator can cause large losses in the core end iron during underexcited operation. The steady state power stability limit indicates the maximum real power that can be delivered at constant field voltage. The effect of the high initial response AVR is to substantially increase the steady state stability limit. The generator must must be constrained to operate in the underexcited region in an area where the unit would be stable if a transfer were made to the field regulator. The thermal limit is usually more restrictive than the power stability limit. The default scaling scaling of the UEL curve described is based on the generator capability curve. The intent is is to protect the generator from end iron heating effects by setting the UEL approximately 10% above the underexcited reactive capability curve. The 10% is chosen to give give sufficient safety margin. The stability limit is a function of the network to which the generator generator is connected. The customer is is responsible for system stability protection settings. If the customer supplies UEL curve points, enter those values instead of the values from the method described.

4-5.2.1. UEL OPERATION. This section describes the UEL operation which is performed by a combination of standard blocks (see Figure 3-7). The capability of a generator when plotted on a reactive power versus real power plot changes as terminal voltage changes. This means that a number number of curves are required to provide protection over the normal 10% terminal voltage range permitted by the AVR. If the real and reactive power signals signals are

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normalized by dividing by the square of the terminal voltage then the capability of the generator becomes a single curve. The generator watts signal is first normalized by dividing by the square of the filtered voltage signal. The resulting normalized power is then filtered and absoluted. This value is is fed to the function generator block where the normalized pu UEL curve has been entered. The output of the function function generator block is the UEL curve point corresponding to that value of generator real power output. This value then then becomes the UEL limit allowed. This UEL limit as read from the curve is normalized VARs and must be multiplied by the square of the filtered voltage signal to produce a VAR reference for the proportional proportional plus integral integral regulator. The PI regulator is enabled by an AND gate if 52G is closed and the AVR is in control. It compares measured generator VARs feedback quantity with a reference limit derived from the UEL curve to generate an error signal which feeds the regulator. The output of the PI regulator block is fed to a limiter set to allow allow only positive outputs. This value is then fed to the excitation autosetpoint block ASP@UE input. It is added to the existing existing AVR setpoint to produce an increase in the excitation level sufficient to prevent the excitation decreasing below the level corresponding to the UEL limit curve chosen.

4-5.2.2. UEL SCALING AND CONFIGURATION. Configuring and scaling the UEL function involves setting the PI regulator for proper gain and time constants. It also includes includes setting the UEL curve based on the generator capability curve. The UEL limiter uses uses process regulator #1. This is a proportional plus integral regulator. A PI regulator has the form: Kp + Ki/s where Kp = proportional proportional gain and Ki = integral gain (rads/sec). Only two sets of adjustments for the UEL regulator are necessary. One for exciters using a normal bandwidth AVR and one for those customers requiring a higher bandwidth, such as a fast


response/high gain AVR. The default setting setting is normal bandwidth. normal bandwidth. The recommended settings are as follows: Normal EE.5899 = 200 (Ki = 2 rads/sec) EE.5900 = 819 (Kp = 3.2) High EE.5899 = 200 (Ki = 2 rads/sec) EE.5900 = 410 (Kp = 1.6)

NOTE Two EEPROM values are set because the command and feedback gains are independently adjustable. Steady state stability of the UEL can be verified by operating the generator at various power levels then slowly lowering the excitation to drive the generator into the limit curve. Dynamic closed loop loop response can then be verified by stepping the AVR setpoint using the excitation autosetpoint block extra input ASP@EX. A step of 1 or 2% is sufficient. If it is not permissible to drive the generator into its true limit curve then the curve could be reset at a safer level and the testing performed using this curve.

4-5.2.3. UEL CURVE. The UEL limit curve is obtained by using a general purpose background function generator block. This is a five point piecewise linear function function generator. The function is flat to the left of Y0, the first point, and to the right of Y4, the last point. point. The X coordinates must must be monotonically increasing X0

Generator Data:

100000 k VA 3600 RPM 0.85 PF 40 °C cold gas 13800 V

1 pu power at unity power factor = 100 MW = 5000 counts. This value was was defined during primary scaling of the generator voltage and current feedbacks. The EX2000 calculates watts and VARs from measured generator voltages and currents. If the customer has not specified UEL settings, the following recommended settings can be used: Recommended X coordinates are at 0.3, 0.6, 0.9, and 1.2 pu MW. X = 0 is the X coordinate for Y0 point and needs to to be entered. This gives the following values: X1 = 0.3 pu = 0.3*5000 counts = +1500 = EE.2864 (from the example curve this is equivalent to 30.0 MW) X2 = 0.6 pu = 0.6*5000 counts = +3000 = EE.2866 (from the example curve this is equivalent to 60.0 MW) X3 = 0.9 pu = 0.9*5000 counts = +4500 = EE.2868 (from the example curve this is equivalent to 90.0 MW) X4 = 1.2 pu = 1.2*5000 counts = +6000 = EE.2870 (from the example curve this is equivalent to 120.0 MW)

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Next, the Y coordinates must be chosen. This method selects Y values 10% above the rated capability curve to to provide ample ample safety margin. If more than one curve is given for different gas temperatures, use the the rated curve. In the example example given this is 40 °C cold gas. From the chosen customer reactive capability curve, read the VARs at 0 power. This is -35 MVARs. Add 10% 10% of rated kVA (not 10% of the reading) to define the Y0 point. Y0 = -35 + (10% * 100) = -25 MVARs. MVARs. This value must now be changed to counts to store in EE.2872. EE.2872 = (-25/100)*5000 (-25/100)*5000 counts = -1250 counts = Y0 Y1, Y2 and Y3 are obtained as follows: Y1 = -40 MVARs + 10 = -30 = -1500 counts = EE.2865 Y2 = -35 MVARs + 10 = -25 = -1250 counts = EE.2867 Y3 = -17 MVARs + 10 = -07 = -350 counts = EE.2869 The final value Y4 is chosen differently. A straight line is drawn from the Y3 point through the 1 pu at unity power factor point to intersect the X = 1.2 pu power line. This gives Y4 = -2*Y3 -2*Y3 = -2 * -350 = +700 counts = EE.2871. EE.2871. All this is based based on the assumption that the 0.9 pu power point on the capability curve yields a negative value and the final segment passes through rated k VA at unity power factor. The final point point Y4 is chosen this way because this gives better coordination with loss of excitation protection.

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Figure 4.1 UEL Curve

4-5.3. Reactive Current Compensator (RCC) The RCC signal is used to compensate for insufficient reactance between generators or when there is too much reactance. The RCC simulates a reactance on the generator output. If reactive current increases, the amount subtracted from the autosetpoint also increases. This lowers the excitation voltage and therefore the amount of VARs produced by the generator. It provides a drooping characteristic to insure that the load reactive power is equally divided between paralleled machines. Generally this compensation is required if machines are paralleled directly on the same bus. If generators are paralleled on the high side of their generator step-up transformer, then sufficient reactance should exist between the generators so that additional compensation is not required. The factory default setting is zero compensation. Determine the amount of compensation necessary

during initial startup. The compensation is set to the minimum required to ensure VAR sharing. Values of 3% to 6% reactance are usually sufficient. (Alternatively, EE.3791 ASPRCC can be set to a negative value to provide line drop compensation LDC). RCC is set by EE.3791 ASPRCC, reactive current gain. The range of this setting is ± 12.5% compensation. The setting for the +12.5% compensation is 32768 counts, or 2621.44 counts per percent compensation. If an RCC of 4% reactance is desired, set EE.3791 = 4*2621.44 = 10486. If LDC is required, EE.3791 is set to a negative value. For a 4% line reactance, or line drop compensation, set EE.3791 = -10486.


4-5.4. VAR/Power Factor Control A VAR/Power Factor controller can be provided as an optional regulator in the regulator core. Either VAR control where a constant generator VAR output is maintained or power factor control where a constant generator power factor is maintained can be selected. The two control actions are, of course, mutually exclusive. The PF/VAR controller can be configured to latch to the existing PF or generator VAR output when the associated control action is initiated. The operator station is used to enable the PF/VAR controller. The operator must adjust the generator to the VAR output or PF that it is desired to maintain. The appropriate operator station button is then pushed to latch the output at the desired value. To release the control action, the same button is pushed a second time.

4-5.4.1. VAR//PF CONTROL OPERATION AND CONFIGURATION. The PF/VAR control block uses the generator VARs and Watts as its feedback variables. These inputs are selected by EE.3718 PF@VAR, normally pointed to VAR.1153, generator VARs and EE.3719 PF@WAT, normally pointed to VAR.1152, generator watts. The watt and var signals pass through low pass filters both of which are set by EE.3723 PFLPFW. A setting of 5 rad/sec is typically used (where 100=1 r/s). The filtered VAR signal is fed to a latch and the negative input of the controller summing junction. The latch gets set when VAR control is selected. The input variable that controls VAR control selection is set by EE.3717 PF@ENV. When this variable is true, VAR control is selected. The latch holds the value of VARs that was measured as the latch was set. This latched variable is fed to a switch. The switch is configured by EE.3720 PFARK. If PFARK is set to 0, then the switch will pass the latched value of VARs to be regulated. If PFARK is set at a non zero value then the generator output VARs corresponding to this count value will be maintained. This feature is typically not used.

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The preset or latched VAR setting is fed to a second switch that will pass either the VAR or PF reference to a summing junction depending on which control action has been selected. If the VAR setting was chosen, the VAR reference will be fed to the summing junction where the actual VAR feedback will be subtracted to create an error signal. This error signal passes through a deadband set by EE.3722 PFDEBD (5000 counts = 1 pu). The deadband setting should be chosen so that excessive regulation does not occur while the required setting is accurately maintained. From the dead band function a raise or lower signal is given to the exciter as required to maintain the value selected. The raise signal is PFVRAISE VAR.718 and the lower is PFVLOWER VAR.719. The power factor controller functions in a similar fashion. The VAR signal is multiplied by 32768 and then divided by the watt signal. The resultant is the normalized tan of the angle between watts and vars where 32768 equals a tangent of unity (45 degrees). The resultant is filtered and then feeds a latch that will be set if the PF control function is selected. The output of the latch feeds a switch configured by EE.3721 PFVWTK. If PFVWTK is set to zero the latched value is passed. If PFVWTK is set to a nonzero value, then the angle represented by the setting of EE.3721 will be regulated. A non-zero value is typically not used. The output of this switch is multiplied with the actual generator watts and divided by 32768. The resultant is the generator VARs necessary to maintain the desired PF angle at the new generator real power level. This becomes the reference to the controllers summing junction, where an error signal is developed which causes the exciter to raise or lower the generator VAR output to hold the desired power factor. The same deadband setting applies to either the PF or VAR controller.

NOTE The algorithm does not calculate the cosine of the angle between the generator watts and vars so does not explicitly develop a signal representing the PF of the generator.

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4-5.5. Field Regulator (FVR) The FVR (manual) regulates the exciter field without reference to the generator terminal voltage. It is possible to configure the field regulator to regulate one of four variables. Either main generator field quantities IFG and VFG or exciter field quantities IFE and VFE are selectable. For the EX2000 PWM, the field regulator is configured as a current regulator with IFE as the feedback variable . Normal regulator operation is in automatic voltage regulator with transfer to the manual regulator only occurring as a result of losing the generator terminal voltage feedback signal(s) due to PT failure detection. The PTFD detector is disabled off-line in certain configurations. In this case, the field current regulator (OEL) serves to limit the regulator output to prevent overfluxing the generator. The operator has the capability to switch the exciter to manual regulation by an operator station command (see Figure 3-5). In automatic regulator, the field regulator receives an input from the auto voltage regulator and acts as an inner loop regulator in an attempt to cancel the effects of the time constant of the rotating equipment. This allows for greater speed of response when operating in automatic r egulator. The AVR output is limited to 2 pu exciter field current so as not to overdrive the regulator output.


The manual (backup) regulator tracks the field current necessary to maintain the existing generator terminal voltage. This tracking is delayed to avoid following transient fluctuations or erroneous AVR behavior. The ramp range is typically set for 70% of AFNLex to 120% AFFLex in 120 secs. The output of the REF2 block is passed through a software switch to the EX2000 core block and then to the MCP block as the field regulator adjust command MFLDADJ VAR.165.

4-5.5.2. REF2 SCALING AND CONFIGURATION. The present for the manual voltage regulator RUN1REF EE.91 is set to a count value for *0% of AFNLex . Set EE.91 = (0.8*AFNLex*5000/AFFLex) = 1476. The REF2 ramp high limit is set to 120% of AFFLex. Set RF2THO EE.3444 = 1.2*5000 = 6000. The REF2 ramp low limit is set to 70% AFNLex. Set RF2LO EE.3442 = .07*(3.52/9.54)*5000 = 1291 Typically the ramp time to cover this range is set for 120 secs. Set RF2SLM EE.3446 = 0 for 1/10 bit/sec rate and RF2NRT EE.3451 = ((6000 1291)/120)*10 = 392. Tracking delay, set RF2WLG EE.3447 = 50

4-5.5.3. FVR OPERATION. The field regulator 4-5.5.1. REF2 OPERATION. The increase/decrease reference block normally supplies the field regulator reference to the core block EXCOR. This reference block is identical in structure to the REF1 block used by the AVR. During exciter startup, the output of REF2 tracks, without delay, the value pointed to RF2@T3. This is EE.91 RUN1RF register. RUN1RF is set to the count value representing 80 percent of AFNLex. Normal increase/decrease control is disabled at this time. If the exciter is in AUTO regulator and is not detected to be in limit then the output of REF2 tracks the variable pointed to by RF2@T2 which is normally IFE.

adjust command MFLDADJ VAR.165, which normally originates as the REF2 output or a reference signal from the AVR, becomes the reference for the field regulator. This reference feeds a summing junction. A feedback signal representing IFE is subtracted from this reference to give an error signal (FLOPERR VAR.1003) for the PI regulator. The output of the field regulator (FLOPO VAR.1004) goes to a minimum value gate where it is compared with the field current regulator output (ILOPO VAR.1002). The minimum of the two becomes the net firing command (FIRCMD VAR.1000).


4-5.5.4. FVR SCALING. The field regulator is set to cancel the effects of the time constant of the rotating equipment by setting Kp/ Ki = T’d0 of the exciter. With the loop gain set to unity, the transfer functions of the inner loop reduce to be Ki = (2*pi*f*VFFLex @75 C)/(Bridge Gain*5000). The bridge gain is the actual DC link voltage divided by 11775, maximum firing command counts. The field regulator bandwidth for the EX2000 PWM regulator is chosen to be 10 Hz. In the example system, VFFL ex is 9.54 * 5.810 = 55.4. The bridge gain is calculated as 137 volts/11775 or .0116. Ki is calculated to be (2*pi*10*55.4)/(.0116*5000) = 60 Set FLDIG0 EE.1551 = 60*65.536 = 3932 counts. Since Kp/Ki was set to equal the time constant of the exciter, in the example system, Kp = Ki *0.35 or 21. From this, EE.1550 FLDPG0= 21 * 256 = 5376 counts. FLDTGO EE.1547 sets the tracking filter for 2 secs. Set EE.1547 = 1/2 * 65.536 =33 (where 65.536 = 1 rad/sec)

4-5.5.5. TRANSFER TRACKING METER AND BALANCE. There is automatic tracking between the manual and automatic regulators in either direction with independent tracking delays. A balance meter is normally provided on the operator station to show the amount of unbalance that exists between the regulators. While in the auto regulator, the unbalance is shown as the magnitude of exciter field voltage unbalance that exists. If a transfer is made at this time to the manual regulator, the exciter field voltage jumps by this amount. While in the manual regulator, the balance is shown as the generator terminal voltage unbalance that exists.

4-5.6. Field Current Regulator (FCR) The Field Current Regulator (FCR) is programmed within the MCP Block. This regulator is also a proportional plus integral (PI) regulator. The FCR has a feature that allows for two sets of proportional and integral gains to be entered. The FCR can then be switched between these two sets of gains through

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a command (EFA@EN) to the Core Block. These two sets of gains are referred to as the primary field current regulator and the alternate field current regulator. The primary current regulator is enabled when FCR@EN EE.3706 is true. The alternate current regulator is enabled when both EFA@EN EE.3705 and FCR@EN are true. The EX2000 PWM uses both of these current regulators as an Overexcitation Limiter (OEL) to limit exciter field current (and therefore main generator field current). The alternate FCR gains and primary FCR gains are set exactly the same as the field regulator gains since the field regulator in the EX2000 PWM is configured as a current regulator. The alternate current regulator is always enabled unless an extended forcing condition is detected, and is used as an instantaneous current limit. It has two setpoints, one for on-line and one for off-line operation. The primary current regulator is used as an inverse time limiter. Forcing is allowed for up to 10 seconds. If forcing is maintained for 10 seconds, the alternate current regulator is disabled with control switching to the primary regulator. The primary regulator will then drop the current to its on-line setpoint until the inverse time block activates and then control is limited to 1 pu exciter field current. In the off-line situation, instantaneous exciter field current is limited to 125% (or less) of AFNLex to prevent overfluxing the generator and connected transformers. On-line, the instantaneous current is limited to prevent heating (I 2t) damage to the main field winding. However, it must allow proper field forcing for fault support before beginning its current limit function. When either the primary or alternate current limiter takes control of IGBT bridge gate firing, an OEL Active annunciation is displayed on or sent to the operator interface. The control of bridge firing is determined by a function referred to as a minimum value gate. The field regulator cannot resume control of bridge firing until the firing reference generated by AVR or FVR becomes lower than the firing signal limit out of the current regulator. See Figure 3-8.

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4-5.6.1. ALTERNATE FCR. Off-line, the alternate FCR limits the exciter field current to protect against overfluxing the machine and any connected transformers. It is a backup V/Hz limit with the actual V/Hz limiter in the excitation autosetpoint block serving as a primary limiter. Online, the alternate current regulator serves to limit the exciter field current to a level that protects the rotating diodes in the brushless exciter. The alternate field current regulator is enabled whenever EFA@EN true. Until the generator output breaker is closed, it will limit field current to the value in EE.82, the off-line instantaneous setpoint. Once the 52G breaker closes, the alternate current regulator limit is switched to the value in EE.80. As stated before, since the field regulator (FVR) is configured as a current regulator in the EX2000 PWM, the proportional and integral gains for the alternate current regulator are identical to those in the FVR.

4-5.6.2. ALTERNATE FIELD CURRENT REGULATOR SCALING. EE.1541 IRGKA0 is the alternate FCR proportional gain. From the calculations for the FVR in the example system, Kp for the current regulator is 21. EE.1541 will then be the same as EE.1550 = 256*Kp = 5376. EE.1543 IRWIA0 is the alternate FCR integral gain. From the calculations for the FVR in the example system, Ki for the current regulator is 60. EE.1543 will then be the same as EE.1551 = 65.536*Ki = 3932. EE.1545 ILOPA0 is the alternate FCR preset value. In the EX2000 PWM, this is chosen to be 120% of the firing command for exciter field AFNL. For the example system, this would be (1.2*VFNLex@25 C*11775)/actual DC link voltage. EE.1545 = (1.2*3.52*4.871*11775)/137 = 1768 counts. The off-line setpoint for the alternate current regulator is stored in EE.82. This value is 125% of AFNLex which for the example system would be 1.25*3.52/5000 = 2306 counts.


The on-line setpoint for instantaneous current limit must allow for forcing of the regulator during system transients. Generally, calculations are made that specify a ceiling from the exciter to support 2 pu capability from the generator. The rotating exciter diodes can be a limiting factor in what this on-line forcing capability is. In the EX2000 PWM, this current level is conservatively chosen to be the maximum of either 140% AFFL ex or twice AFSIex unless a higher value is specified by the original equipment manufacturer. In the example system, 1.4 * AFFLex = 13.356. Two times AFSIex = 2 * 6.236 = 12.472. There is also a specified ceiling limit of 14.45 amps. EE..80 will then be 15.45 * 5000 /9.54 = 8097 counts. Before changing this instantaneous limit to a higher value, GE generator engineering should be consulted. An off-line protection block, PRITC, is provided as an instantaneous trip if the pickup setpoint is exceeded when the EX2000 PWM regulator senses the unit is off-line. It is set to a value above the offline alternate field current regulator setting. If this level is reached, the regulator will immediately stop IGBT gating. The PRITC block is set up for linear error with pure integration (1 sec integration time). The pick up value is set to 1.25 AFNLex with the limit being activated as soon as the pickup level is exceeded. Set PITJMP = 2. This sets the PRITC block for excessive I*t function . Set PITPU = 125% of AFNLex For the example system 1.25*(3.52/9.54)*5000 = 2306 counts the PRITC begins to accumulate when PITPU is exceeded. PITTRP is set such that the unit will stop gating at a value of 160% of AFNLex. For the example system, this would be 645 counts. The trip setting is counts above the pick up level for a trip.


4-5.6.3. PRIMARY FCR. The primary field current regulator is used to limit main generator field current to a value so as not to exceed the thermal capability of the field copper. This limit must be imposed on the EX2000 PWM output current into the exciter field in order to limit the calculated main generator field current. The setpoints of the primary FCR are generally set to 125% of AFFLex until the inverse time protection is enabled and then output current is limited to 1 pu AFFLex. Forcing on-line is allowed until the reference level stored in a signal level detector (SLD1) is exceeded for 10 seconds or by a protection inverse time block being in limit (PIT1LIM = true). The SLD level is set for 140% of AFFL. The protection inverse time block, PRIT1, is set to begin timing at 1.06 pu exciter current and will activate the second level of field current at 1.25 pu after 60 seconds. The field regulator setpoint must be lowered below the level of the field current regulators in order to release control from the FCR or FCA.

4-5.6.4. PRIMARY CURRENT REGULATOR SCALING AND CONFIGURATION. EE.1540. IRGKC0 is the primary FCR proportional gain. From the calculations for the FVR in the example system, Kp for the current regulator is 21. EE.1540 will then be the same as EE.1550 = 256*Kp = 5376. EE.1542 IRWIC0 is the primary FCR integral gain. From the calculations for the FVR in the example system, Ki for the current regulator is 60. EE.1542 will then be the same as EE.1551 = 65.536*Ki = 3932. EE.1548 ILOPP0 is the primary FCR preset value. In the EX2000 PWM, this is chosen to call for full gating of the IGBT bridge. In the example system, this would be 11775 counts. The high level setpoint for the primary current regulator is stored in EE.83. This value is 125% of AFFLex which for the example system would be 1.25*5000 = 6250 counts. After the PRIT1 block times out, the current will then be reduced to the lower level setpoint for the primary current regulator which is stored in EE.81.

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This value is 100% of AFFLex which is equal to 5000 counts. For SLD1, the level that the input (IFE) is to be compared with is set in EE.152 SL1LEV. This value is set to 140% of AFFLex or 7000 counts. SLD1 pickup time delay EE.154 = 1000 (for 10 second pickup) The PRIT1 is an inverse time protection block. The scaling is set on a per unit basis of AFFL. As all machines are scaled to produce 5000 counts at AFFL then the values should not change on an individual job basis. The PRIT1 block is scaled for I*t function with a sixty second leaky integrator. Set EE.3749.0 PITJMP = 0 This sets the PRIT block for excessive I*t function (protect for field heating). Set EE.3749.1 = 0 This sets the PRIT block with a 60 second integrator. Set EE.3751 PITPU = 5100 which is 102% of AFFLex. The protection block will begin to integrate when PIT@IN exceeds 102% AFFL. Set PITDEL EE.3755, integrator leak gain to 16122 counts. This setting allows the PRIT1 block to begin accumulating but never reaches a point where it will generate a trip. Essentially sets the accumulation level to 1.06% of AFFL ex. A trip level can be set in PITTRP EE.3752. If a trip is used, a setting of 783 will cause a trip signal output in 120 secs at 112% AFFLex and 42.3 secs at 125% of AFFLex. A transfer level can be set in PITTRF EE.3753 If a transfer is used, a setting of 666 will cause a transfer action at 85% of the trip level. PITDEL is set to 0 in EE.3755 so that pure integration is used. A constant error signal will produce a linear ramp of (PIT@IN -PITPU) counts/sec.

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4-6. OPTIONAL FUNCTIONS SCALING AND CONFIGURATION Several optional functions are available with the EX2000 PWM regulator on brushless exciters. These include exciter field temperature calculation, field ground detection, and 4 - 20 ma output transducers. The requisition specific elementary should be consulted to determine which, if any, of these options have been supplied.

The MX address is the maximum input value (EE101 = DAC1, EE103 = DAC2, EE105 = MET1, and EE107 = MET2) •

DAC1 and DAC2 can be offset by the values stored in DAC1OF and DAC2OF

For example, to bring up this function: 1. In the Parameter Mode, call up EE100-DAC1 and EE101-DAC1MX (select EE.100).

4-6.1. Transducer Outputs

2. Enter the signal to be monitored into EE.100.

The DAC1, DAC2, MET1, and MET2 analog outputs are available for test purposes and are typically used as the input reference for up to four isolated 4-20 ma output transducers. The four outputs operate identically and are programmed similarly to the variables in Test 11. DAC1 and DAC2 have 12 bit resolution and are updated 720 times per second. MET1 and MET2 have eight bit resolution and are updated 360 times per second.

Putting that RAM address in EE.100 produces that signal at the NTB/3TB board’s DA1 testpoint and DAC1 terminal (3TB-53).

Each output has two addresses (see Table 4-1).

Typically, the DAC and MET outputs are assigned with exciter volts (VFE), exciter amps (IFE), transfer volts, and occasionally exciter field temperature. Consult the elementary for the specific requisition to see which transducers are supplied, if any. Typically, DAC1 is exciter field temp, DAC2 is transfer balance, MET1 is IFE and MET2 is filtered VFE.

•

The @ I address selects the variable to be output (EE100 = DAC1, EE102 = DAC2, EE104 = MET1, and EE106 = MET2)

DAC2, MET1, and MET2 function like DAC1. When a signal’s RAM address is loaded into the DAC and MET addresses, the signal is output on the NTB/3TB testpoints and terminal points listed in Table 4-1.

Table 4-1. Diagnostic Mode Analog Output Points Loaded into Address

NTB TP

Terminal Board Point

EE.100-DAC@1 & EE101-DAC1MX EE.108-DAC1OF

DA1

DA1, 3TB-53

EE102-DAC@2 & EE103-DAC2MX EE.109 DAC2OF

DA2

DA2,3TB-55

EE104-MET@1 & EE105-MET1MX

MET1

MET1, 3TB-54

EE106-MET@2 & EE107-MET2MX

MET2

MET2, 3TB-56


4-6.2. Ground Detector And Diode Fault Monitor The EX2000 PWM is capable of interfacing with a brushless regulator field ground detector module. There are several different styles of ground detectors available, some with multiple inputs to the EX2000 PWM, some with only one input. The most common of these detectors is configured as follows. This detector requires a 24 volt supply, typically passed through the EX2000 PWM cabinet. The detector returns three signals to the EX2000. These are a Ground Detector Malfunction alarm, a Ground Fault alarm, and a Diode Fault alarm. These three inputs are taken into the EX2000 PWM controls on the NTB board at inputs V4VCO, FDBVCO, and REFVCO. These inputs are configurable voltage controlled oscillators which convert the analog input to dc counts for use in the regulator. The Detector Malfunction alarm signal is a nominal 2 V dc when there is no fault present. This signal is scaled in the FBVCO and compared to a fixed reference in a signal level detect. A high signal (nominally 20 V dc) indicates a detector malfunction. The Ground Fault alarm is a nominal 10 to 24 V dc unless a ground fault is detected. Then the input will go to a nominal 2 V dc. This signal is scaled in the V4VCO, compared to a fixed reference and passed through a time delay such that the condition must persist for up to 10 seconds. It is ANDED with the inverse of the detector malfunction alarm. This prevents a false ground detection if the detector has indicated that it is not healthy. To prevent inadvertent alarms when the unit is not operating, the ground fault detector is not activated until the EX2000 PWM has been running for 15 secs. It is always disabled while in simulator mode to prevent false alarms or inadvertant operation of the customer lockout. The Diode Fault alarm sends a one hertz, 0 to 24 volt squarewave to the EX2000 PWM. This signal is scaled in the REFVCO. It is then sent to two signal level detectors. One checks for a continuously low voltage which indicates a diode fault. The other checks for a continuously high voltage which indicates a diode monitor fault.

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Each of the inputs and resulting signal level detect outputs are incorporated in the global alarm string 30EX and also passed over the status S page.

4-6.2.1. GROUND DETECTOR AND DIODE FAULT SCALING AND CONFIGURATION. The Ground Detector Malfunction input is scaled in the FBVCO. The feed back VCO scale factor EE.1386 FVSCL0 is set to a value of 10000. This scales VAR.183 to a nominal 20000 counts with an input of 20 V dc. EE.180 SL5LEV is the level that the input variable from the FBVCO is compared to. This is set to a value of 18000. The mode of the level detect is set to a 0 in EE.178.11 SL5MODE. The level detect will then pick up when the input is greater than or equal to the sensing level. The level detect time delay is set to 0.5 seconds with a setting of 50 in EE.182 SL5PUT. The Ground Detection input is scaled in the V4VCO. The V4VCO scale factor EE.488 V4SCL0 is set to a value of 10609. This scales VAR.185 to a nominal 20000 counts with an input of 24 V dc. This variable is compared to EE.74 in the CMPR1 block. EE.74 is a general purpose register and is set to a value of 2000 counts. If the output of V4VCO is greater than 2000 counts, then there is no ground. The delay of 10 seconds is set in the ONDLY3 block at EE.5670 ONDLY3. This is set to a value of 1000 for a 10 second delay. The Diode Fault input is scaled in the REFVCO. The feed back VCO scale factor EE.1281 RVSCL0 is set to a value of 10000. This scales VAR.182 to a nominal 20000 counts with an input of 20 V dc. For a diode monitor fault detection, EE.187 SL6LEV is the level that the input variable from the RFVCO is compared to. This is set to a value of 18000. The mode of the level detect is set to a 0 in EE.185.11 SL6MODE. The level detect will then pick up when the input is greater than or equal to the sensing level. The level detect time delay is set to 2 seconds with a setting of 200 in EE.189 SL6PUT. For a diode fault detection, EE.194 SL7LEV is the level that the input variable from the REFVCO is compared to. This is set to a value of 2000. The mode of the level detect is set to a 4 in EE.192.11 SL7MODE. The level detect will then pick up when

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the input is less than the sensing level. The level detect time delay is set to 2 seconds with a setting of 200 in EE.196 SL7PUT.

4-6.3. Field Thermal Model The EX2000 PWM monitors the temperature of the exciter field windings by calculating the field winding resistance from the measured values of exciter field voltage and exciter field current. In simulator mode, the model uses the simulated values of field voltage and current.


The field current IFE (VAR.1016), after passing through a filter, feeds a limiter that only passes field current values greater than 500 counts. The signal then becomes the denominator of the divide function. The result of the divide function is the field resistance in counts. Restricting the denominator to values above 500 counts eliminates the possibility of division by zero.

From the calculated field resistance, the temperature of the windings is calculated using the resistance formula for copper. This temperature is stored in VAR.1011, where it is displayed in degrees centigrade. It can be read directly or sent over the LAN to the operator station.

The resulting resistance count value is normalized to Kelvin degrees by multiplying by a scale factor set EE.1594 ERTSFO. The Kelvin degrees are then converted back to centigrade by subtracting 235. The temperature, now in degrees centigrade, is filtered and passed though a limiter that restricts the output temperature range to 0 to 300 °. The temperature is output as VAR.1011 EFG, scaled at 1 count equals 1 °C. Due to the time constants, field temperature is not accurately modeled during startup and shutdown of the exciter.

4-6.3.1. THERMAL MODEL OPERATION.

4-6.3.2. THERMAL MODEL SCALING. The

The voltage feedback, VFE (VAR.1014), passes through a limiter that restricts it to positive values. This prevents negative values of resistance from being calculated. The resulting voltage signal is fed through a filter that matches the field voltage to the associated field current. This is accomplished by producing a lag that approximates the lag experienced by the field current due to the field time constant. The amount of lag is set using EE.1596 EFLTCO.

example system uses VFE and IFE as the feedback variables. The model parameters to be set are ERTSF0 and EFTLC0.

A switch is used to select either field voltage or a value of zero. Field voltage is the output if bridge firing is detected (VAR.882 MPWRENAB is true). This signal becomes the numerator in a divide function.

EE.1594 = 32*360*5000*(234.5+25)/(9.54*20000*4.871) = 16082 counts.

EE.1594 ERTSCO - Exciter thermal model resistance to degrees scale factor is set = (32 * Max V dc link * 5000 * (234.5+t1)) / (AFFLex*20000*(Rf@t1) From the sample data: DC link volts = 360 V dc; AFFL ex = 9.54 A dc ; Rf@25C = 4.871 ohms.

The exciter lag field time constant is set by EE.1596. From the sample data, the open circuit exciter field time constant is 0.35 seconds. It will be set to (4096 * 0.458752)/ (T’do exciter).


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CHAPTER 5 STARTUP CHECKS

5-1. INTRODUCTION This chapter contains basic checks to perform after installation and during initial startup. Consult and study all furnished drawings and instructions before starting installation. These include outline drawings, connection diagrams, and elementary diagrams. For installation details, refer to applicable sections of GEH-6011 and GEI-100228 Receiving, Storing, and Warranty Instructions. These checks are not intended as complete commissioning instructions for the EX2000 PWM regulator, but serve as a guide for the sequence of tests and a description of functions and devices requiring field tests.

WARNING Before application of any power source to this equipment, be sure that no tools or other objects left over from unpacking or installation are present in the cabinets, including the bridge assembly.

5-2. EX2000 PRESTART CHECKS Each EX2000 PWM is thoroughly tested before shipment. This testing process should ensure that the regulator will perform properly upon receipt and loading of requisition specific software. A complete inspection of the EX2000 PWM regulator and associated equipment should be performed prior to energization of any portion of the regulator controls. Items to look for are shipping damage to wiring or circuit boards, installation damage or foreign objects from the

installation process, contamination due to improper storage, and loosening of connections and components. Proper grounding and separation of wiring levels should also be maintained. Ensure that the ground connection is sized properly and is connected to a suitable ground point.

5-2.1. Energization And Simulator Control Checks The following steps are intended as guide for installation and initial startup of the EX2000 PWM regulators. Site specific procedures should incorporate these steps to ensure completeness. 1. Verify hardware, proms, and board revisions using the ST2000 or Control System Toolbox and job specific software supplied with the equipment. Hardware to check includes the shunt supplied, dynamic discharge resistor, charge control resistor, and options supplied. If changes to proms or circuit boards are required, a Full Calc in ST2000 or Control System Toolbox may be needed. Contact GE Motors & Industrial Systems before changing any values generated by the Full Calc if unsure of the correct settings. 2. Verify jumpers and switch settings as specified in ST2000 or Control System Toolbox and the requisition elementary. If changes are made, update the application tool databases to keep an accurate documentation of the regulator. 3. Perform a complete wire check of all external connections to the EX2000 PWM. Inspections for unintentional shorts, induced voltages, correct wiring ampacities, and the like should be

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made. This will include PT and CT inputs, alarm contacts, trip contacts, and connections to the operator’s interface device. Ground detector connections and other optional equipment should also be checked. 4. With input disconnects open, check incoming ac and dc power for proper levels and polarities. On units with a PMG input, it may not be practical to check the PMG inputs until initial roll of the equipment. At a minimum, a complete wire check of the inputs should be performed. 5. Energize the dc power supply feed to energize exciter regulator controls. The EX2000 PWM will go through an initialization process. During this initialization process, hardware and firmware diagnostic checks are performed. Any faults generated during the initialization should be corrected before proceeding. If an IOS or UC2000 is supplied on the system, communication faults will not be cleared until the IOS or UC2000 is operational. The LDCC display will default to its normal, deenergized state. It should appear similar to the following. A S 97%

I

0%

The PSCD board has several LED indications of power supply levels and test points for checking the output of the regulator supplies. Check these testpoints for appropriate voltage levels. Refer to the ST2000 help messages or the individual board GEI instructions for test points and voltages. The DC link voltage should also be checked. Variable VAR.1091 should read the corresponding voltage in engineering units and should agree with the level measured. On the IAXS board, connections PL and NL are the positive and negative link voltages respectively. 6. Turn off the dc supply and repeat the PSCD supply voltage checks for the ac feed to the EX2000 PWM regulator. The PSCD board voltages will be the same as for the dc feed. The DC link voltage will generally be different than the DC link with only the dc supply voltage.

Phase rotation of the ac input is not important in the EX2000 PWM regulator. But phasing should be checked to ensure accuracy in as built drawings. If a single phase ac input is used, it must be connected to L1 and L3 leads of the ac input device. If voltage doubling is required, the connections on CTBA-3 and CTBA-4 should be made. Refer to the control elementaries for proper connections. After independent proper operation with both the ac and dc source voltages are observed, both power sources should be energized at the same time. Elimination of either source should have no noticeable affect on the EX2000 PWM regulator. Only the dc link voltage may be affected. This check should be performed during power checks and on-line operation as well. 7. Using ST2000 or Control System Toolbox, download the appropriate core file to the EX2000 PWM regulator. After the download is complete, the regulator will again perform a diagnostic check. 8. In order to thoroughly test the operation of the EX2000 PWM regulator, operation in the simulator mode is recommended. Place the control core in the simulator mode (EE.570.0=1). See Chapter 6 for operation and scaling information of the simulator. It is also recommended that as much testing be performed in simulator mode as possible. This should help shorten the pre-startup and initial roll checks greatly since control functions, alarms, trips, etc. will have been tested and verified correct.

NOTE In the simulator mode, the EX2000 can generate a request for lockout. This can trip the lockout relay unless the function is disabled.


9. It may be necessary to place temporary jumpers on inputs to simulate breaker closures or start permissives that may not be operable at this time. One such input is to reset the lockout relay (86) or place a temporary jumper to simulate lockout relay. Refer to hardware elementaries for specific jumpers required. If temporary jumpers are used, it is important to remember to check the operation of these inputs from the actual devices at some point during the pre-start process. 10.If the operator’s station device is available, a start from this device may be given and proper operation of the controls should be tested and observed. Raise and lower signals, alarms, limits, displays and transducer outputs are available in the simulator mode. 11.Close or jumper circuit breaker auxiliary contact (52G) input to simulate on-line operation. Change EE.84 value to simulate higher turbine load. UEL settings can be checked by increasing EE.84 lowering the regulator output, and comparing to the capability curve.

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a. Off-line OEL While in manual regulator, raise the excitation level until the field current exceeds the off-line OEL pickup level. The system goes into off-line OEL. Lower the reference to see that the OEL condition resets. Step the reference into OEL and observe the response. Return the summation block test input to zero. b. On-line OEL While in manual regulator and with about 90% MW load, increase the VARs until field current is above 112% of AFFL. The PRIT1 block begins to accumulate and after a time delay activates the OEL limiter. Lower the setpoint and then step the reference so that the system goes back into on-line OEL. Observe the response and be aware that if a very large step is used, the signal level detector pickup level is also exceeded. After 10 seconds, the exciter field current will be limited to 125% of AFFLex and when PRIT1 times out it will limit to 100% of AFFL ex. After completion of the tests, be sure to disconnect the test oscillator.

NOTE Return EE.84 value to (152*frequency/60) before opening the 52G contact or the simulator will overspeed and cause a trip. 12. Verification of the operation of the on-line and off-line OEL Limiters can be accomplished through the use of the built in simulator and ST2000. A convenient way to do this is to utilize the two input summation (2 Input Sum) block that is programmed between the REF2 block output and the CORE block EFR@SP input. EFR@SP is the setpoint for the field regulator. The summation block was added to the pattern for test purposes only. Input 1 of this block is the normal field regulator reference supplied by REF2 output. Input 2 can be pointed to the output of the background test oscillator. In this manner the regulator can be easily stepped.

5-3. PRE-START POWER CHECKS 1. After proper simulator operation, remove the control core from simulator mode. As described in section 4-4.4 Feedback Offsets, the inputs from the current and voltage feedbacks should be adjusted.. These offsets are found in location EE.1508 through EE.1513. In simulator mode, these values are not in use and therefore do not affect the simulator operation. 2. Check PT and CT inputs by applying an input signal with a 3-phase source at rated PT secondary volts and CT secondary current. The operator station device should display rated terminal volts. Internal control variables for PT and CT feedbacks should be verified for proper scaling. If supplied, a PT failure can be checked by opening the primary switch and observing a transfer to the backup PTs or a transfer to the manual regulator.

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3. It is recommended that the brushless exciter field be used for initial power tests. There should be no detrimental effects to using the exciter field as a load since the unit is not rotating and can not produce generator field voltage. If the exciter field is not available, a suitable replacement load must be used. This dummy load has to be inductive. If a simple resistive load is used the control will trip on instanteous over current before the regulator can limit the current. Since the EX2000 PWM regulator is a current regulator, it should be sized to carry at least AFFLex in order to keep as many EE settings at the requisition levels as possible. Choosing a smaller current load will require adjustment of several operating parameters. 4. Place the controls in manual regulator. Connect an oscilloscope and voltmeter to the output load leads. Incorrect shunt wiring can cause the EX2000 PWM regulator to turn full on in manual mode. Verify shunt connections with a millivolt source, observing proper polarities, before starting.

5. Upon starting the regulator, exciter field current should develop to approximately 80% AFNL. Immediately stop the controls if any unusual or abnormal operation occurs. Operation in the automatic regulator is not recommended since the regulator will be open loop and be very difficult to control. 6. Measure field voltage and current and compare to the operator station display values. Use ST2000 or Control System Toolbox to check the VCO output counts for proper values. While the scaling can be adjusted to give the desired counts for the indicated voltages or currents, it is generally an indication of improper scaling or jumper settings when these values are not in agreement. 7. Check field output waveshapes using an oscilloscope. Observe for stable operation at low and full output voltages. The display should be a square wave similar to Figure 5-1. As output is raised, the on-time will increase as the off-time will decrease. The upper and lower peaks of the square wave will be equal to the dc link voltage.

Again, test jumpers or operation of the 86G device will be required to run the EX2000 PWM regulator into the exciter field or replacement load.

DC LINK LEVEL

O VOLTS LEVEL LOW OUTPUT

HIGH OUTPUT

Figure 5-1. Typical Output Wave Forms


8. Use the method outlined in the OEL simulator testing section 5-2, step 12 to verify off-line and on-line OEL limit and regulator stability. A jumper for the 52G input will be required to simulate on-line operation. It will not be necessary to simulate MW’s on the EX2000 PWM regulator. Raising the output current to the OEL settings should result in OEL limiter operation as described. For checks without the actual exciter field, it is possible to simulate higher current levels by changing the value in EE.1505. This value should be restored to the original setting after testing. If found to be unstable, contact GE Motors & Industrial Systems for any changes in settings. 9. Restore values and reconnect for normal operation. Check temporary inputs, jumpers and EE values and restore to the desired operational settings. The unit is now ready for off-line, initial roll system checks.

5-4. INITIAL ROLL OFF-LINE CHECKS 1. Run the unit up to synchronous speed. At this time the PMG input may be available for the first time. Before applying the PMG input, measure and observe correct PMG inputs. Refer to applicable PMG instruction manuals for more information. 2. With the EX2000 PWM regulator in manual control, start the exciter. The unit should come up to approximately 80% amps field no load. This should result in a build up of generator terminal voltage no greater than rated terminal volts when operating at rated generator frequency. 3. Refer to applicable instruction manuals for initial startup checks for the rotating portions of the brushless exciter and main generator. This should include ground detector operational checks as well.

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4. Check phasing of the PT inputs. CT inputs will not be available at this time. Measure for correct secondary values at rated generator terminal volts. Negative generator frequency counts are indicative of improper phase rotation of the PT inputs. Check for the values of exciter field volts and exciter field current at no load used to scale the exciter. Measure the actual field volts and field shunt millivolts. The measured values, counts and operator station display values should be in agreement. 5. Step tests of the exciter field regulator should be performed to ensure stable operation. Step test the field voltage regulator using the input summing block as described in the OEL simulator testing. 6. Transfer to automatic regulator. The transfer should be smooth and without any noticeable fluctuations in generator or regulator operation. The AVR can be stepped by pointing the extra reference in the Excitation Autosetpoint Block (EE.3781 ASP@EX) to the output of the test oscillator. Generally a 2% step (400 counts) is sufficient. Verify stability of the AVR. 7. Give the regulator a stop command. With the unit in automatic regulator, restart the exciter and watch for proper operation. The EX2000 should bring the generator to rated terminal volts (or the setting of the EE.3402 pointer). 8. The V/HZ regulator function can be checked by slowing the generator and, while in automatic regulator, watching the ac terminal volts drop accordingly. A 1.10 pu ratio should not be exceeded. The EX2000 PWM regulator is now ready for online operation. Return the unit to rated terminal volts. Initial synchronization checks for other equipment may be required at this time.

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5-5. ON-LINE CHECKS 1. It is recommended that the unit be synchronized in manual regulator the first time. The CT inputs to the EX2000 PWM regulator can adversely affect the automatic regulator operation if they are not correct. Once the unit has been synchronized, increase the unit load for a small amount of generator line current. Check the MW and MVAR displays for positive values. If they are negative, the CT leads connections may be reversed. This condition should be corrected before proceeding. If there are no CT disconnects, the unit must be off-line to reverse/change CT connections.

WARNING

Reversing CT leads with the unit under load can cause substantial damage to generator components. The unit must be off-line, 52G open, before correcting CT lead polarity. 2. After correct displays of MW and MVars has been ascertained, place the regulator in automatic. For units without PT failure detection, remove the main PT input by opening the disconnect switch (if supplied) or pulling the PTCT board input connection plug. This generates a PT undervoltage alarm. The operator station display should indicate that the regulator has transferred to manual, and can not be placed into automatic. A 30EX global alarm should be generated. Restoring the PT input and operating the PT BAD reset will allow a return to automatic. Activating the automatic regulator selection should again place the exciter in automatic regulator. The 30EX alarm should be clear. Two PT inputs are required for PT failure detection. Opening the main PT will generate a PT failure alarm but the unit will not transfer to manual. It will continue regulation on the secondary set of PTs. Restoring the main PT input will clear the PT bad alarm.

Removing only the secondary PT input will generate a PTX alarm but will not transfer the unit from automatic to manual. Restoring the PT input will clear the alarm. Removing both the primary and backup PT inputs will generate the PT undervoltage alarm and the restoration process described above should be followed. 3. Check UEL operation. The simulator checks should be sufficient to guarantee proper operation of the UEL at the desired setpoints as long as the line current and line voltage count values are correct. Many customers may require verification of the actual UEL limit line. If this is needed, the UEL stability should be checked first. Stability of the UEL can be checked by raising the UEL setpoints to a value of just slightly underexcited. The values of EE.2872, EE.2865, EE.2867, and EE.2869 should be set to negative 250 counts. Lower the excitation slowly until the UEL regulator takes over at the revised settings. The EX2000 PWM regulator can then be stepped into the UEL regulator using the extra input to the auto setpoint block as described in section 5-4, step 8. This will verify that the UEL operation is stable. Contact GE Motors & Industrial Systems if any instability in the UEL regulator is encountered. If at any time undesired operation is observed, a transfer to manual regulator should correct the condition. After verification of UEL stability, the original UEL setpoints should be restored. If the customer desires testing of the actual UEL limits, the excitation can be slowly lowered into the limit. 4. The on-line OEL testing performed in section 53, step 7 should be sufficient. To perform the same test on the actual machine requires operation at very high field current levels. GE Motors & Industrial Systems does not recommend that the equipment be actually driven into OEL. If it is required, contact GE Motors & Industrial Systems.


After completion of all EX2000 tests, restore all storage registers used for testing to normal values, back up the software, and disable all write enables. As the unit is loaded, check for reactive sharing between paralleled units. Reactive current compensation can be introduced through the AVR setpoint block by changing the gain of the RCC. See EE.3791 help for changing the RCC gain.

5-6. OPERATOR INTERFACE The EX2000 PWM regulator is a versatile regulator, capable of communicating with several different Human-Machine Interfaces. Direct communication with the GE turbine control is the standard, primary operator’s station and interface to the EX2000 PWM. The communication configuration is defined and standardized within both the turbine controller and the EX2000 PWM. Changes to the Status S page and communication settings should be made only under advisement from GE Motors and Industrial Systems.

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Check out of the Status S communications should be carried out in conjunction with the turbine control startup procedures. Usually it is sufficient to verify control of operator functions as described on the interface control panel or screen.

5-6.1. Units With UC2000 or IOS All UC2000s and IOSs are factory-tested and operable when shipped to the installation site. Final checks should be made after installation and before starting the UC2000/OC2000 combination or the IOS. Consult the appropriate equipment GEH for guidelines for inspections to perform prior to startup. GEH-6335 GEH-6334 GEH-6122

Operator Console 2000 Operation and Maintenance Unit Controller 2000 Operation and Maintenance Intelligent Operators Station Operation and Maintenance

5-6.2. Units With Discrete Switches And Meters Testing of contact inputs and outputs fr om discrete meters and switches should include a thorough wiring check for continuity and no direct shorts before powering the devices from the EX2000 PWM. Normal startup checkouts will ensure correct connections and operation of the devices.

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Notes:


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CHAPTER 6 SIMULATOR SCALING AND OPERATION

6-1. EX2000 PWM SIMULATOR A simulator is built into the EX2000 PWM that can model a generator and brushless excitation system off-line or on-line (connected to an infinite bus). Simulator operation is selected by setting EE.570.0 = 1. When selected, the feedbacks presented to the control regulators are switched, by software, from the real feedback inputs to feedbacks derived by mathematical models mimicking the generator and field circuit behavior. The EX2000 PWM controls react in a manner close to the way they would react in normal operation. The simulator can serve as a valuable startup, maintenance, and training tool.

The exciter regulator can be raised and lowered in automatic or manual regulator, both on-line or offline. The regulator limits come in at the same levels as in non-simulated operation. The regulator responses provide a good representation of what can be expected of the real system in response to step changes. By changing the storage register containing the value representing model shaft torque, EE.84, it is possible to raise or lower the generator real power output when simulating on-line operation. The exciter changes the system VARs in response to changes in the exciter setpoints.

CAUTION The simulator is scaled to represent the actual system as accurately as possible. This means that when a start command is given to the EX2000, it follows a normal start sequence. Close commands are sent to the bridge contactor but gating of the IGBT devices is disabled. The controls look for actual auxiliary contact feedbacks representing the contactor states. If these are not correct the appropriate faults are generated. The generator armature and field models, as well as the exciter stator and field models, provide the feedbacks for exciter field voltage and current and generator stator voltage and current. These feedbacks are handled by the transducering algorithms the same way real feedbacks are used to calculate watts, VARs, speed deviation, and frequency. If the model scaling is correct, the display data cannot be distinguished from real data. Main generator field voltages and currents are also simulated internally and used for correct model operation.

Disable the IGBT gating while in simulator mode. Check that setting of EE.589.14 = 0.

6-1.1. Simulator Scaling The goal of the simulator scaling is to make the models represent, as close as possible, the behavior of the real system. In addition to the following EE settings, see EE.3850 GMJMPR in section 4-3. Generator, exciter, and regulator parameters listed in section 42 for the example system will be used for scaling discussions in the simulator section. SMVDCL0 EE.1558 simulates the dc link voltage of the EX2000 PWM regulator. It is set to represent the actual running voltage of the dc link. For the example system this is 137 V dc. For EE.1558, set equal to 137/360 * 20000 = 7611 counts.

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SMHST0 EE.1559 is the simulated heat sink temperature of the PWM IGBT heatsink. This value can be used to test the overtemperature alarm and trip levels in the regulator controls. One count equals 1 °C. Normally set to maximum expected temperature during operation, 60 °C. GMVBAT EE.3851 represents simulator flashing voltage. Since flashing is not required on the EX2000 PWM regulators, set EE.3851 = 0. GMRBAT EE.3852 represents simulator battery resistance for field flashing. This is also not required in the EX2000 PWM and EE.3852 is also set to a 0. GMVTHY EE.3853 is the simulator thyrite voltage. This models an overvoltage protection thyrite connected across the exciter field input. The example system has a 125 V exciter field. Set EE.3853 = (Exciter field class*7.2*1797)/(DC link volts) = (125*7.2*1797)/137 = 11805. GMRDIS EE.3854 simulates the dynamic discharge resistance. Set EE.3854 = (AFNLex*2*RDD*30664) / DC link volts = (3.52*2*17*30664)/137 = 26787. GM_RFE EE.3855 is the simulator exciter field resistance. This is set equal to (VFNL ex /DC link volts) * 31108 where VFNL ex = AFNLex * Rfe@25C. From the example data Rfe@25c = 4.871 ohms. VFNLex = 4.871 * 3.52 = 17.15 V dc. Set EE.3855 = (17.15/137)*31108 = 3838. GMILFE EE.3856 represents the inverse of exciter field inductance. EE.3856 is set equal to (DC link volts * 156) / (VFNL ex * T’doex). T'doex is the open circuit field time constant which is 0.35 seconds in the example system. Set EE.3856 = (137*156) / (17.15 * 0.35) = 3561. GM_RFG EE.3857 simulates generator field resistance. This parameter is normally set to 7115 * frequency/60. The constant scaling is the result of expected normalizations. Exciter AFNL is expected to produce VFNL on the generator field which in turn produces AFNL on the generator field. Set EE.3857 = 7115 for the example, which is a 60 Hz system.


GMILFG EE.3858 is the simulated inverse of generator field inductance. Set equal to (60/ frequency) * 670 / T'do gen, where T'do is the main generator field time constant. Set EE.3858 = 670/5.615 = 119 for the example system. GMVFES EE.3859 is the simulator exciter voltage scale down divider. This scales the exciter voltage from the model to produce EXSIMFE VAR.1177 (simulated exciter field voltage). Set EE.3859 = 5888 * maximum dc link volts / dc link volts = 5888 * 360/137 = 15472. GMIFES EE.3860 is the simulator exciter current scale down divider. This parameter scales the exciter current from the model to make EXSIMIFE VAR.1176 (simulated exciter field current). Set EE.3860 = (AFFLex /AFNLex)*3146 = (3.52/9.54)*3146 = 8526. GMVFGS EE.3861 is the simulator generator field voltage scale down divider. This parameter scales generator field voltage from the model to make EXSIMVFG VAR.1163. Set GMVFGS to 27329280/ (AFNLgen * RFG@100 C* 20000 / Maximum DC link volts). In the example system, and simplifying the formula, this is 1367 * 360 / (313*0.256) = 6139. GMIFGS EE.3862 is the simulator generator field current scale down divider. This parameter scales generator field current from the model to make EXSIMIFG VAR.1161 (simulated generator field current). When used in conjunction with standard scaling, such as AFFL = 5000 counts, set GMIFGS = (AFFLgen / AFNLgen ) * 3146. In the example system, this would be 846/313*3146 = 8503. GMIFLS EE.3863 represents the simulator flashing current scale down divider. This parameter is not used in the EX2000 PWM regulator. Set GMVIFLS = 0. GMDAMP EE.3864 is the simulator generator model damping factor where 1 count = 0.11 pu watts/pu speed(60 Hz). Normally EE.3864 is set equal to 400. If oscillations occur while operating in simulator mode, try changing GMDAMP.


GM_IXS EE.3865 represents the generator model inverse of synchronous reactance. This parameter models the generator synchronous reactance in simulator mode. GM_IXS = 4096/Xs(pu). To most accurately model the generator, it is necessary to approximate the generator synchronous reactance from no load to full load. In a real system, machine reactances vary with saturation and saliency. Therefore it is necessary to make simplifying assumptions that produce a value of Xs that provides reasonable behavior over the range VFNL to VFFL. Assume a round rotor machine with no saturation, no saliency, and resistance is negligible. This makes the direct and quadrature reactances equal. If this level of accuracy in the model is not of concern then Xd (the direct axis saturated synchronous reactance) can be used. If optimum model accuracy is of concern then the following method, based on a simplified synchronous machine model, can be used. The range of field amps from no load to full load = AFFL/AFNL=9.54/3.52 = 2.71. If a phasor diagram showing the machine operating at rated load and power factor connected to an infinite bus at rated terminal volts is drawn then a quadratic equation with the synchronous impedance as the unknown quantity can be generated and solved for Xs. It is then used in the above equation for GM_IXS. The rated power factor for the sample machine is 0.85. With the machine operating at rated k VA = 1 pu k VA then rated real power = 0.85*1 pu and rated reactive power output = 0.53*1 pu Generator voltage = 1 pu As per unit values are being used it is not necessary to use the actual generator MW and MVAR values involved. From the phasor diagram, the following quadratic equation results where the generator internal voltage range required is represented by the ratio of AFFL to AFNL = 2.71 (2.71)**2 = (1 + 0.53*Xs)**2 + (0.85*Xs)**2 Solving for Xs gives a synchronous reactance of 2.04 pu

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Set EE.3865 equal to 4096/Xs = 4096/2.04 = 2007. GMXEXS EE.3866 models the effect of external reactance for the simulator generator model. This can be set for a strongly or weakly connected system. EE.3866 is set equal to 65536*Xe/(Xs + Xe) where Xe represents the amount of impedance in per unit connecting the generator to the system. For the example, set for a strong system (small amount of impedance between generator and system), with Xe = 0.1 pu, then EE.3866 = 65536*(0.1)/(2.04 + 0.1) = 3062. GM_IM EE.3867 models the effect of generator inertia for the simulator. Typically, the default value of zero (which is equivalent to M = 3.98 pu) is used. For more accurate simulator modeling, EE.3867 can be set to (frequency/60)*16302/M where M =2H, the generator inertia constant.

6-1.2. Operation To put the control core into simulator mode set EE.570.0 = 1. The shaft speed of the generator increases to rated (synchronous) speed at a rate determined by the simulator inertia constant and the level of shaft torque preset in register EE.84. The value of torque preset to give rated speed at no load is 153 * (frequency/60). Rated speed is indicated on the core programmer display as 100%. The shaft torque can be altered on-line or off-line by changing the value stored in EE.84. Off-line, changing shaft torque increases the speed and hence the fre quency of the generator. Changing the torque on-line increases or decreases the real power output of the model generator. To start the simulator, it is generally necessary to wait until the simulated generator speed is above 95%. It is also necessary to have the 86G input to the EX2000 PWM regulator closed. Failure to do so

GEH-6375


will result in a fault 29 when attempting a start. Starts in auto or manual regulator are permissible. The simulator can be started from the operators station or by pressing the RUN button on the LDCC keypad. After starting, exciter field current and voltage and generator terminal voltage will build up to the preset levels of the regulator being used.

CAUTION Once the simulator is on-line, the 94EX contact output can be operated inadvertently. This may cause unintentional operation of protective devices outside the EX2000 PWM regulator. Lifting of the 94EX output contacts is recommended during simulator operation.

To put the simulator on-line, a contact closure simulating 52G aux contact feedback must be input to core LTB input IN1. Some oscillations are generally observed when closing the 52G contact since there is no synchroscope to confirm closing while the simulated generator and line voltages are in phase. When off-line, changing the exciter AVR or MVR setting adjusts generator terminal voltage. When on-line, raise or lower signals change the generator VARs. The result of these control changes can be observed. Testing of UEL settings, V/hz regulator, over current protections, and so on, can also be observed. Feedback and control signals from the operators station and 4-20 ma outputs (if supplied) can also be observed. When stopping the simulator, the reference value in EE.84 should be returned to the original level for 100% speed off-line. Failure to do so will result in unusual off-line operation.

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