Commissioning Motor Control Centers

Engineering Encyclopedia Saudi Aramco DeskTop Standards

Commissioning Motor Control Centers

Note: The source of the technical material in this volume is the Professional Engineering Development Program (PEDP) of Engineering Services. Warning: The material contained in this document was developed for Saudi Aramco and is intended for the exclusive use of Saudi Aramco’s employees. Any material contained in this document which is not already in the public domain may not be copied, reproduced, sold, given, or disclosed to third parties, or otherwise used in whole, or in part, without the written permission of the Vice President, Engineering Services, Saudi Aramco.

Chapter : Electrical File Reference: EEX30204

For additional information on this subject, contact W.A. Roussel on 874-6160

Engineering Encyclopedia

Electrical Commissioning Motor Control Centers

Content

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INTRODUCTION................................................................................................................ 1 SAUDI ARAMCO REQUIREMENTS................................................................................. 2 Low Voltage ............................................................................................................. 2 Medium Voltage........................................................................................................ 4 EVALUATING MOTOR CONTROL CENTERS UPON RECEIPT.................................... 6 Visual Inspection....................................................................................................... 6 Verification Against Specification.............................................................................. 6 EVALUATING MOTOR CONTROL CENTER INSTALLATION AND TESTING........... 9 Visual Inspections ..................................................................................................... 9 Suitability .....................................................................................................10 Physical Damage...........................................................................................11 Alignment .....................................................................................................11 Cleanliness....................................................................................................11 Contactor/Controller Mechanism ..................................................................12 Lubrication ...................................................................................................12 Mechanical Inspections.............................................................................................12 Bolt Torque ..................................................................................................13 Open/Close Operation...................................................................................13 Main Contact Check .....................................................................................13 Door Operation ............................................................................................14 Electrical Inspections and Tests ................................................................................14 Point-to-Point Wiring ...................................................................................15 Megger.........................................................................................................15 Contact Resistance........................................................................................16 DC High-Pot ................................................................................................16

Saudi Aramco DeskTop Standards



SYSTEM PRE-OPERATIONAL CHECK-OUT .................................................................18 SYSTEM OPERATIONAL CHECK-OUT..........................................................................19 WORK AID 1: REFERENCES FOR EVALUATING MOTOR CONTROL CENTERS UPON RECEIPT..................................................20 Work Aid 1A: MCC Applications Checklist..............................................................20 Work Aid 1B: Low Voltage MCC Ratings ...............................................................20 Work Aid 1C: Low Voltage MCC Terminal Board Wiring .......................................21 Work Aid 1D: Minimum Low Voltage Indoor Motor Control Center Technical Requirements.....................................................................22 Work Aid 1E: Medium Voltage MCC Ratings..........................................................32 Work Aid 1F: Medium Voltage MCC Requirements.................................................33 WORK AID 2: REFERENCES FOR EVALUATING MOTOR CONTROL CENTER INSTALLATION AND TESTING.........................40 Work Aid 2A: MCC Commissioning Electrical Test Values......................................40 Work Aid 2B: Information, Formulas, and Tables for Use in Evaluating the Results of Insulation Resistance (Megger) Tests ..........................41 Work Aid 2C: Information, Formulas, and Tables for Use in Evaluating the Results of DC Hi-Pot Tests..........................................................42 Work Aid 2E: Excerpts from GI 2.710 .....................................................................50 GLOSSARY........................................................................................................................54




Table of Figures

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Figure 1: Typical Low Voltage MCC ...................................................................... 4 Figure 4: Low Voltage MCC Terminal Board Wiring Type Features (From NEMA ICS 2-322) .......................................................................21 Figure 4: Low Voltage MCC Terminal Board Wiring Type Features (From NEMA ICS 2-322) (Cont'd) .........................................................22 Figure 5: Saudi Aramco Low Voltage MCC General Requirements (From 16-SAMSS-503) ..........................................................................23 Figure 6: Saudi Aramco Low Voltage MCC Construction Requirements (From 16-SAMSS-503) ..........................................................................24 Figure 6: Saudi Aramco Low Voltage MCC Construction Requirements (From 16-SAMSS-503) (Cont'd).............................................................25 Figure 7: Saudi Aramco Low Voltage MCC Enclosure and Isolating Panel Requirements (From 16-SAMSS-503) ...........................................26 Figure 8: Saudi Aramco Low Voltage MCC Bus and Space Heater Requirements (From 16-SAMSS-503) ....................................................27 Figure 8: Saudi Aramco Low Voltage MCC Bus and Space Heater Requirements (From 16-SAMSS-503) (Cont'd).......................................28 Figure 9: Saudi Aramco Low Voltage MCC Nameplates, Wiring, and Miscellaneous Equipment Requirements (From 16-SAMSS-503) ............29 Figure 9: Saudi Aramco Low Voltage MCC Nameplates, Wiring, and Miscellaneous Equipment Requirements (From 16-SAMSS-503) (Cont'd) ..................................................................................................30 Figure 10: Data Schedule for Low Voltage Switchracks and MCCs (From 16-SAMSS-503) ..........................................................................31 Figure 11: Ratings for Class E2 (Fused) Medium Voltage Motor Controllers (From SADP-P-116 and NEMA ICS 2-324) ...........................................32 Figure 12: Saudi Aramco Medium Voltage MCC General Requirements (From 16-SAMSS-506) ..........................................................................33 Figure 13: Saudi Aramco Medium Voltage MCC Construction and Design (From 16-SAMSS-506) ..........................................................................34 Figure 13: Saudi Aramco Medium Voltage MCC Construction and Design Requirements (From 16-SAMSS-506) (Cont'd) ...........................35




Figure 14: Saudi Aramco Medium Voltage MCC Enclosure and Isolating Panel Requirements (From 16-SAMSS-506).............................35 Figure 15: Saudi Aramco Medium Voltage MCC Bus and Space Heater Requirements (From 16-SAMSS-506) .........................................36 Figure 16: Saudi Aramco Medium Voltage MCC Nameplates, Wiring, and Miscellaneous Equipment Requirements (From 16-SAMSS-506) ............37 Figure 16: Saudi Aramco Medium Voltage MCC Nameplates, Wiring, and Miscellaneous Equipment Requirements (From 16-SAMSS-506) (Cont'd).............................................................38 Figure 16: Saudi Aramco Medium Voltage MCC Nameplates, Wiring, and Miscellaneous Equipment Requirements (From 16-SAMSS-506) (Cont'd).............................................................39 Figure 17: Dielectric Absorption Ratio Chart ...........................................................41 Figure 18: Example of DC Hi-Pot Test (Good and Bad Insulation) ..........................42 Figure 19: Saudi Aramco Pre-Commissioning Form, P-018, Motor Control Centers............................................................................44 Figure 19: Saudi Aramco Pre-Commissioning Form, P-018, Motor Control Centers (Cont'd) ..............................................................45 Figure 19: Saudi Aramco Pre-Commissioning Form, P-018, Motor Control Centers (Cont'd) ..............................................................46 Figure 19: Saudi Aramco Pre-Commissioning Form, P-018, Motor Control Centers (Cont'd) ..............................................................47 Figure 19: Saudi Aramco Pre-Commissioning Form, P-018, Motor Control Centers (Cont'd) ..............................................................48 Figure 19: Saudi Aramco Pre-Commissioning Form, P-018, Motor Control Centers (Cont'd) ..............................................................49 Figure 20: GI 2.710 Excerpt ....................................................................................51 Figure 20: GI 2.710 Excerpt (Cont'd).......................................................................52 Figure 20: GI 2.710 Excerpt (Cont'd).......................................................................53




INTRODUCTION Motor control centers (MCCs) are used when the centralized control of a number of motors is possible and desired. MCCs function as a control location in which branch circuit incoming and outgoing lines are marshalled. The modular designs of MCCs allow for convenient motor control grouping that provides conservation of space and construction flexibility. Once the MCC for a given installation is chosen, the MCC is ordered, shipped, received, inspected, installed, and tested during the commissioning process. The commissioning process for MCCs in Saudi Aramco facilities ensures that a safe and cost-effective system is installed that performs to the specifications of the facility for the projected operating lifetime of the facility. Experience has shown that the time and effort that is expended up front to ensure safety, quality control, and adherence to Saudi Aramco and industry standards minimize subsequent equipment failure. The MCC commissioning process involves evaluations, verifications, and checks that determine whether the proper MCC specifications and installation requirements are met. Tests are also performed to determine whether the electric power distribution system will operate properly and safely after the MCC installation. When the MCC is inspected and tested satisfactorily during the commissioning process, the system should operate in accordance with manufacturer's specifications for its maximum useful life. This Module provides information on the following topics that are pertinent to commissioning motor control centers for Saudi Aramco installations: • Saudi Aramco Requirements • Evaluating Motor Control Centers Upon Receipt • Evaluating Motor Control Center Installation and Testing • System Pre-Operational Check-Out • System Operational Check-Out


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SAUDI ARAMCO REQUIREMENTS Large process and process support equipment relies on motors for primary and ancillary functions throughout the manufacturing process (e.g., fans, circulation pumps, and blowers). The motor power distribution, protection, and control equipment that is contained in an MCC are small but important parts of the electric power system. It is usually advantageous to group motor controllers at an MCC, which saves space, simplifies cabling, and frequently makes it possible to install the control equipment in an air-conditioned room. For Saudi Aramco installations, it is preferable to group controllers in a substation or control room instead of on switchracks that are located in hazardous areas. An MCC provides centralized power distribution and control of a group of motors. Centralized motor control eliminates the need for trips to local control stations for equipment startups and shutdowns. Convenient grouping of motor control circuits at an MCC also reduces the installation costs. Westinghouse, Powell, and GE-type motor control centers utilizing Westinghouse and GE vacuum starters are an example of some of the MCCs used in Saudi Aramco installations. In Saudi Aramco installations, MCCs are grouped into two voltage levels: low voltage (0-600 V) and medium voltage (2400 and 4160 V). This section of the Module contains information on Saudi Aramco low and medium voltage MCC requirements. Low Voltage To commission low voltage MCCs, it is important for the commissioning engineer to be familiar with the requirements for MCCs that are used in Saudi Aramco installations. This section will briefly describe general Saudi Aramco low voltage MCC requirements. Due to the environmental conditions in Saudi Aramco installations, the only outdoor low voltage MCCs that are allowed are those MCCs that are of the switchrack construction. Specific Saudi Aramco low voltage MCC requirements (e.g., enclosure and bus requirements) are provided in Work Aid 1. NEMA ICS 2-322 classifies low voltage MCCs into the following two classes: Class I and Class II. Class I MCCs consist of a group of combination starters or controllers that are operationally independent. These starters or controllers do not include interlocking or control connections between units. Class II MCCs consist of a group of combination starters or controllers that are operationally related to each other for specific applications (e.g., sequence control). Class II MCCs include interlocking and control wiring between units.


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Class I or Class II low voltage MCCs that are used in Saudi Aramco installations must be rigid, free-standing, metal-enclosed structures that are designed in accordance with NEMA Class I, Type B. Figure 1 shows a typical low voltage MCC. Low voltage MCCs consist of vertical sections that are assembled into a group. Because low voltage MCCs that are used in Saudi Aramco installations must be suitable for back-to-wall or back-to-back mounting, they should only contain front-mounted equipment (e.g., breakers, controllers, and switches). Each vertical section grouping has a common power bus and that forms an enclosure to which additional sections may readily be added. Each MCC vertical section is subdivided into compartments that contain the various control and protective devices. Field rearrangement of MCC compartments into any possible combination is accomplished through use of simple fasteners, such as bolts and screws. The line side of MCC incomers must be provided with meters (e.g., ammeters and voltmeters). All control and protective devices that are installed in the MCC are selected so that they will operate properly in the designated atmosphere without further protection. To prevent overheating, MCCs are fitted with ventilation openings that are filtered or screened to prevent the entrance of rodents and other foreign matter. Control device assemblies are arranged so the assemblies can be removed for maintenance or repair without deenergizing the MCC (e.g., plug-in line connections). Although fuses are an integral part of the control and protective device design in most industrial installations, circuit breakers are preferred over fuses for Saudi Aramco installations because of the inherent single-phasing characteristics of fuses. Saudi Aramco practice does not normally include the use of capacitors that are directly connected to the terminals of motors or motor control centers on low voltage systems.


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Figure 1: Typical Low Voltage MCC

Medium Voltage This section will briefly describe general Saudi Aramco medium voltage MCC requirements. Specific Saudi Aramco medium voltage MCC requirements (e.g., construction and design requirements) are provided in Work Aid 1.


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NEMA Class E1 controllers and starters are not used in Saudi Aramco installations because of their inherently low short-circuit interrupting ratings. NEMA Class E2 controllers are used for medium voltage motors (2300 V and 4000 V motors) up through 1100 kW (4000 hp). Class E2 starters and controllers can be grouped to form motor control centers if the fault level does not exceed the interrupting capacities that are listed in Figure 11 of Work Aid 1; however, controllers should not be fabricated back-to-back or stacked over one-high. Two-high arrangements were previously allowed; however, only one-high controllers are now allowed. NEMA Class E2 controller fuses should be carefully chosen to ensure optimum coordination with the overload relays and the relays of other breakers on the system. A static motor protection (multi-function) relay that provides protection against single phasing should be specified and implemented because NEMA standard ICS does not require the fuses to open all three phases. If the fuses in all three phases do not open when a fault occurs, single phasing is possible. In addition to the protection mentioned above, the medium voltage MCCs should include ground fault relaying. A disconnect should also be provided for each starter as a means of isolating the main contactor. Individual control power transformers must provide a source of control power for each circuit within the MCC. Each motor control center bus must have a voltmeter with a selector switch, and each incoming supply feeder must have an ammeter with a selector switch. A circuit for motor space heating should be provided for each motor circuit that is powered from the MCC. Each motor space heating circuit should have a separate molded case circuit breaker. Additionally, the following items can also be accommodated in an MCC, if required: • A starting reactor, or auto-transformer, that is used for control during reduced voltage motor starting. • A group surge protection device for the motor control bus. • A test source of ac control power that is to be used during controller testing. • A method for excitation control of synchronous motors. (Excitation control is normally provided as a separate unit.)


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EVALUATING MOTOR CONTROL CENTERS UPON RECEIPT The installation of motor control centers (MCCs) is a process that occurs over a period of time. MCCs usually supply power to the motors and pumps that form the base of the manufacturing or refining process. The MCC installations begin with an identified need for pump and motor power distribution and control centers in a new facility. After the facility design is approved, the MCCs are ordered from the manufacturer. When the MCCs are received from the manufacturer, they must be evaluated to ensure that they are proper for the installation. The purpose of the evaluation is to verify that correct MCCs were received from the manufacturer and that the proper equipment specifications and parameters were met. This section will describe how MCCs are evaluated upon receipt. Visual Inspection When MCCs are received from the manufacturer, a visual inspection should be performed. The purpose of the visual inspection is to verify that the MCC components (e.g., controllers and indicating lights) that were received from the manufacturer are in good physical condition and that all of the requested parts and accessories are present. Because damage can occur to the moving parts associated with controllers installed in MCCs, only a cursory inspection is performed at the receiving point. During the cursory inspection, the inspection personnel look for obvious equipment damage and determine whether all necessary support equipment is present. A detailed inspection of the MCCs is performed when they are completely installed at the site or facility. Verification Against Specification When a new facility or facility modification is at the equipment installation stage, the design of the installation has already been completed. The type, the size, and the configuration of the MCC that is selected for a specific power system should be shown in the drawings, the prints, or the specifications for the installation. The purpose of verifying MCCs against the specifications is to ensure that the equipment that is being installed meets Saudi Aramco and industry standards. Generally, the verification against specifications consists of a determination of whether the type and rating of the equipment that is to be installed match the size and type of the equipment that is required for the installation. In some cases, this determination is accomplished by reading an electrical plan that identifies the MCC type, the size, and the configuration.


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During the verification against specifications, the Engineer inspects the manufacturer's nameplate data on each MCC compartment and compares them to the requirements on the electrical plan to determine whether the correct equipment is being used. In other situations, the Electrical Engineer must rely on his knowledge of the correct application of MCCs to determine whether the correct equipment is being used. The data sheets that were used to order the MCC from the manufacturer should also be consulted. An example MCC data sheet is provided in Work Aid 1. Any quality control, quality assurance, and test data that are provided with the MCC should also be reviewed. MCCs that are used in Saudi Aramco power systems should have a nameplate that is clearly visible on the front of the MCC. The nameplate should contain manufacturer-type information. The information that describes the MCC should consist of the manufacturer's name, the type designation (if applicable), and the serial number. Because MCCs may contain different vertical assembly compartments (e.g., controllers) that use control and indicating equipment at various voltages, nameplates should be present at each MCC compartment. Electric power distribution system MCCs are designed to operate at a specific frequency. Saudi Aramco electrical distribution systems are designed to operate at 60 Hz. Medium voltage MCC controller ratings should be in accordance with the table that is provided in Figure 11 of Work Aid 1. Because there are different terminal board arrangements in low voltage MCCs, NEMA ICS 2-322 provides for the different types of terminal board wiring that are required in accordance with the arrangement of the terminal boards. The different types of terminal board wiring are designated Type A, Type B, and Type C. Low voltage MCC power and control leads should be arranged in accordance with Type B. The features that are required by NEMA for Type A, Type B, and Type C are provided in Work Aid 1. MCC bus capacity should be computed through use of the normal full-load current of the largest motor that is supplied by the MCC, all other motors that can be operated at the same time, other loads supplied by the MCC, and future MCC load requirements. The incoming feeder of a low voltage MCC should be provided with a switching device (unless a switching device is already provided at the source of the incoming feeder and it is readily accessible). For low voltage MCCs, the basis for computing the low voltage MCC bus capacity is provided in Work Aid 1. The total MCC bus capacity should be less than the continuous current rating of the main incoming circuit breaker or the fan-cooled current rating of the power source transformer (whichever is most restrictive).


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The low voltage MCC short-circuit rating should not be less than 105% of the maximum available rms symmetrical current available at the MCC line terminals. The short-circuit interrupting rating of the series combination of the MCC component (e.g., circuit breaker, contactor, or thermal overload relay heaters) should be a minimum of 22,000 amperes rms symmetrical. Short circuits are to be computed as the sum of the short-circuit current contributions of the motors that are connected to the motor control center and all other short-circuit current contributions of the supply system at the point of connection to the motor control center.


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EVALUATING MOTOR CONTROL CENTER INSTALLATION AND TESTING MCCs are commissioned to verify that they have been electrically and mechanically assembled and tested and that they conform to the specifications that are designated by the applicable Saudi Aramco and industry standards. Installation inspections are performed to verify that proper MCC installation materials are used, that installation specifications and parameters are met, and that proper installation procedures are followed. The installation inspection is conducted to ensure that MCCs will properly function once they are installed. Electrical tests are performed to check the ability of MCCs to function under all operating conditions and loads. Installation tests should detect shipping or installation damage, gross manufacturing defects, or errors in workmanship or installation. Saudi Aramco Pre-Commissioning Form P-018, Motor Control Centers, contains guidance on the items that should be inspected, checked, and tested during the commissioning of MCC installations. Saudi Aramco Pre-Commissioning Form P-018, Motor Control Centers, is provided in Work Aid 2. The proper evaluation of inspection and testing data during the commissioning process can maximize the operating time of equipment installations by providing a database for equipment that can be used in the future for a determination of trends towards failure. Failure prediction can drastically reduce equipment down-time; if a failure is predicted, operational changes can be made, maintenance can be performed, or equipment that is failing can be replaced in a controlled manner. If a problem is corrected before it causes damage, operating costs will be lower because a malfunction can cause associated (or nearby) equipment damage and disruption of service, or the problem can activate emergency repair crews. A failure in any one of the many inspections, checks, or tests that are performed on MCCs during the installation and testing evaluation is sufficient to prevent the MCC from being commissioned. Visual Inspections Visual inspections are used to assess the physical condition of MCCs. A visual inspection is a pass/fail verification about a particular aspect of the physical condition or the operation of equipment. Because the criteria that are established to determine the acceptability of the visual inspections can be subjective, the visual inspections should be performed by an experienced Electrical Engineer. Visual inspection items are listed in Saudi Aramco Pre-Commissioning Form P-018, Motor Control Centers. Form P-018 is provided in Work Aid 2.


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Because of the large number of inspection items that are associated with MCCs, several courses of action are available for visual inspection failure. The course of action depends on the part of the equipment that failed the visual inspection. A failure of indicating lights or switches can generally be corrected through component replacement. For example, a failure of contactor/controller mechanism inspection or cleanliness inspection can usually be corrected through maintenance procedures. A physical damage or suitability inspection failure will probably require the replacement of the damaged component. The following visual inspections are used to assess the condition of MCCs in Saudi Aramco systems: • Suitability • Physical Damage • Alignment • Cleanliness • Contactor/Controller Mechanism • Lubrication Suitability The purpose of the suitability visual inspection is to determine whether the MCC and the equipment that is contained in the MCC are appropriate for the application. Under normal circumstances, the suitability of the equipment should be determined before the equipment is placed into the system; however, a visual inspection should be performed to ensure that changes that may have been made to the system have not exceeded the voltage and current ratings of the circuit breakers, the contactors, and the fuses that are present in the MCC. To determine the suitability of the MCC, a visual inspection of the nameplate data should be performed and compared to the electrical system single line diagram. For example, if the nameplate information on a controller does not match the ratings of the electrical system diagram, the controller should be replaced with a controller that is correctly rated.


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Physical Damage Physical damage to the MCC or to that equipment that is contained in the MCC can lead to MCC or controller failure during critical system operations. The magnitude of the electric energy that passes through MCCs can propagate and amplify any minor installation damage. Damage to MCCs can lead to catastrophic equipment failure, fire, personal injury, or death. Any physical damage to MCCs that is noted requires the immediate replacement of the damaged component. The most obvious and common forms of physical damage are cracks, dents, missing or broken pieces, bent doors, and burned-out indicator lights. The purpose of the physical damage inspection is to identify whether corrective maintenance or component replacement is necessary. MCCs that show any form of physical damage, no matter how small, should be determined to have failed the physical damage inspection. Alignment The purpose of the alignment inspection is to ensure that the MCCs will properly pass current when they are installed in the electrical system between the power distribution cabinets and the motor loads. Proper alignment of a controller draw-out cubicle frame will ensure that the controller is properly connected to the system when it is installed in the MCC. Stab finger tightness and alignment are also checked during the alignment visual inspection of MCCs. Improper alignment can cause uneven component heating and wear. Due to the construction of controller or contactor draw-out cubicle frames, frames that are out of alignment are usually visually obvious. Cleanliness The purpose of the cleanliness visual inspection is to ensure the proper operation of the MCC over the maximum operating life of the equipment. The accumulation of dirt over a period of time will impede the proper operation of the equipment (e.g., controllers) that is contained in the MCC and will reduce the dielectric strength of the MCC insulation. Dust and dirt can also reduce the speed and sensitivity of a controller or contactor under fault conditions. The accumulation of heavy amounts of dust and dirt should be cleaned away from the draw-out cubicles and wireways of an MCC during maintenance cycles. MCCs that are installed in extremely dirty, dusty, or humid areas may have to be cleaned more often than once during each maintenance cycle.


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Contactor/Controller Mechanism The mechanism assembly of a contactor or controller that is contained in an MCC performs the actual movement of the contacts to supply power to or to remove power from a motor or pump. The purpose of the contactor/controller mechanism inspection is to ensure that moving parts in the contactor/controller operate properly. Proper operation of the contactor/controller mechanism will ensure that the MCC will supply the proper distribution and control for the connected motor circuits. The inspector should visually determine that no obstructions exist that will impede the movement of the contactor/controller mechanism. Lubrication The lubrication visual inspection should be performed in conjunction with the contactor/controller mechanism visual inspection. The purpose of the lubrication visual inspection is to ensure that the moving parts of the contactor/controller mechanisms are properly lubricated and free of rust. Before the application of new lubrication can occur, hardened grease, dirt, and rust should be removed from the surfaces that require lubrication. A cloth that is dampened with kerosene should be used to remove the hardened grease and dirt. Care must be taken to ensure that the cloth does not deposit fibers on the moving parts of contactor/controller. The deposit of cloth fibers on the moving parts can cause subsequent improper mechanism operation. After the proper preparation of the moving parts, a thin layer of lubrication should be applied. Excess lubrication should be wiped off with a clean cloth. Mechanical Inspections A mechanical inspection is used to assess the ability of the MCC and the enclosed equipment to physically perform the mechanical movements that are necessary for proper operation. Tests are also performed during the mechanical inspection to assess MCC safety functions (e.g., breaker trips). Mechanical inspection items are listed in Saudi Aramco Pre-Commissioning Form P-018, Motor Control Centers. Form P-018 is provided in Work Aid 2. Because of the number of mechanical inspection items that are associated with MCCs, there are several courses of action for a mechanical inspection failure. The course of action depends on the part of the equipment that failed the inspection. A failure of mechanism operation can usually be corrected through maintenance procedures. For example, a bolt torque test failure can be corrected through adjustment of the bolts with a torque wrench.


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The following general mechanical inspections and tests are performed on MCCs that are installed in Saudi Aramco systems: • Bolt Torque • Open/Close Operation • Main Contact Check • Door Operation Bolt Torque The purpose of a bolt torque inspection is to ensure that enough force is present to hold the buswork and cubicle frames in place during normal controller or contactor operations and during fault conditions. To determine the amount of force that exists at a bolt, a torque wrench is applied to the bolt in the direction that will tighten the bolt, and the amount of torque is read. Torque values for MCCs are provided in Saudi Aramco Pre-Commissioning Form P-018, Motor Control Centers, that is provided in Work Aid 2. The manufacturer of the MCC will also provide a list of acceptable torques in the MCC technical manual. Open/Close Operation Some MCC contactors or controllers in Saudi Aramco electrical systems can go for long periods of time between operations. A contactor or controller must always be in a condition to operate no matter how infrequently the motor or pump is being used. The purpose of the open/close operation is to check the operation of the breakers and contactors to ensure the freedom of movement of all moving parts. During opening and closing operations, the mechanical condition of all auxiliary devices, bumpers, position indicators, latching, tripping, and operating mechanisms is checked for proper operation. Main Contact Check A check of the main contacts is performed in conjunction with the open/close operation check. The check of the main contacts consists of a pressure check, a contact alignment check, and a check of the full contact area on contactors. The pressure check is performed to ensure that the correct pressure is maintained at the main contact. The correct pressure at the main contacts is necessary to provide a low resistance current path when the MCC is supplying power to a pump or motor. The contact alignment and full contact area checks are performed to maximize the contact surface area at the main contact face. Maximizing the contact surface will provide the lowest resistance in the current path.


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Door Operation Each switchgear circuit breaker compartment must be provided with a door (safety barrier). The door should be provided with a latch that completely closes the compartment when the controller or contactor cubicle is completely installed or removed. The door should have a locking bar to hold the door open. The door should also contain an interlock that prevents the closure of the door unless the cubicle is completely installed or removed. During the mechanical inspection, each cubicle compartment door operating mechanism should be mechanically operated during the mechanical inspection, and the door interlocks (e.g., breaker trips) should be tested. Electrical Inspections and Tests During the commissioning process, electrical inspections and tests are performed to check the ability of MCCs to operate for a reasonable future period of time under all operating conditions and loads. Acceptance or installation tests will usually detect shipping or installation damage and gross defects or errors in workmanship in equipment construction. Once the installation and inspection data have been recorded and assembled, a methodical and consistent program of periodic data collection and evaluation should be established. As each new maintenance item, test, splice, system addition, or system reconfiguration occurs, new inspections and data records will be required and should be added to the existing data on file. Because an electrical inspection or test failure can be caused by a design flaw, construction error, equipment age, or operational misuse, some type of troubleshooting or maintenance activity should be performed on the faulty equipment. For example, a contact resistance test failure can be rectified by cleaning the contacts to remove carbon buildup or by replacing the contacts. Some electrical inspection or test failures are not repairable, and they will require the replacement of the equipment before the MCC can be commissioned. For example, an insulation resistance test failure usually indicates a gross imperfection in the cable, the bus, or the circuit breaker insulation. The following electrical inspections, checks, and tests are performed on MCCs: • Point-to-Point Wiring • Megger • Contact Resistance • DC High-Pot


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Point-to-Point Wiring Point-to-point wiring checks are performed to verify that MCCs comply with Saudi Aramco wiring diagrams and manufacturer's specifications. Terminations and terminal blocks within the MCC are also checked for routing and labeling. During the point-to-point wiring checks, control and metering transformers and fuses (if they are present) are checked for proper application and type. If necessary, adjustments are made to components such as relays, annunciators, alarms, and targets. Megger The purpose of the insulation resistance megger test is to directly measure the insulation resistance of the MCC and the components that are contained in the MCC. In the insulation resistance test, the megger produces a voltage and measures the leakage current, which is calibrated directly in second megohms. The voltage is applied, for example, between the breaker phase and ground, or from phase to phase. The amount of leakage current that is detected results in a meter readout of insulation resistance (in megohms). To conduct the insulation resistance megger test, the megger is connected between each MCC main bus phase ground and the megger is operated. Insulation resistance megger tests must be conducted phase-to-phase and phase-to-ground on all panel buses, outgoing circuits, and PTs and CTs that are contained in the MCC. The line side and the load side of each circuit breaker that is installed in the MCC that is being commissioned must also be megger tested. Because the voltage potentials that are generated during the megger test can damage any connected electronic equipment, megger tests must not be performed on electronic equipment. The insulation resistance values are recorded on a test data sheet or on Saudi Aramco Pre-Commissioning Form P-018, Motor Control Centers, in the recorded test data section. During the commissioning process, the Electrical Engineer should evaluate the insulation resistance (megger) test values to ensure that the insulation resistance values that were recorded are greater than the manufacturer's minimum value. If the manufacturer's minimum value is not provided, the value of the insulation resistance should be greater than the rated voltage +1 kV in megohms. For example, a 600 V rated system must have a measured insulation resistance that is greater than 1.6 megohms. Any value of insulation resistance that is less than the minimum specifications should be investigated by the Electrical Engineer who performs the test data evaluation. The ratio of two time-resistance readings (such as a 60-second reading that is divided by a 30second reading) is called a dielectric absorption ratio. The dielectric absorption ratio is useful in recording information about the insulation. If the ratio is a ten-minute reading that is divided by a one-minute reading, the value is called the polarization index.


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Because constant cranking is required for hand-cranked megger instruments, it is easier to run the test for only 60 seconds and take the first reading at 30 seconds. When a power-operated megger instrument is used, the results of running the test for a full ten minutes and taking readings at one and ten minutes will give the polarization index. An explanation of the evaluation of the dielectric absorption ratio is provided in Work Aid 2. Contact Resistance The purpose of the MCC contact resistance test is to identify contacts that are defective or detrimental to the operation of the circuit breakers, the contactors, or the starters or bus sections that are contained in the MCC. The contact resistance test may also identify loose connections in circuit breakers, contactors, starters, or bus sections. Circuit breakers, contactors, or starters generally have removable cubicles or drawers to facilitate temporary removal for maintenance or testing. Once the equipment is removed from the MCC and with the contacts of the equipment in the closed position, the leads of a digital low-resistance ohmmeter are placed across the line and load sides of the contacts and measurements are taken. A digital low-resistance ohmmeter can deliver enough power to the contacts to make accurate readings that have more validity than those readings that can be obtained through the use of an ordinary multimeter. The contact resistance is recorded on a test data sheet or in the Saudi Aramco Pre-Commissioning Form, P018, Motor Control Centers. Increased contact resistance may be caused by contacts that do not make proper contact or by pitting on the surface of the contacts. The contact resistance values that are recorded should be consistent with manufacturer's recommended values. Generally, values of contact resistance in excess of 200 microohms and deviations of more than +/- 20% should be investigated. Technical data to evaluate the results of the contact resistance test can be found in the circuit breaker manufacturer's technical manual or in the Saudi Aramco Pre-Commissioning Form, P-000, Testing Guide Lines. DC High-Pot The purpose of the dc high potential (high-pot) test is to identify internal faults in or damage to the MCC bus insulation system. The dc high-pot test should be done prior to the initial energization of the MCC and after the megohmmeter test. The dc high-pot testing technique for MCCs involves the measurement of increased dc voltage that is applied to the system under test. The value of the leakage current is tracked as the test voltage is increased through several steps and becomes a criterion of the condition of the MCC insulation. Electrical test reference information for the dc high-pot test is provided in Saudi Aramco PreCommissioning Form, P-000, Testing Guide Lines. A portion of P-000 is provided in Work Aid 2. The electrical test reference information provides the recommended dc high-pot test procedure and test voltages for the various connected equipment voltage ratings.


16



During the high-pot test, the leakage current is plotted against time at the end of each timing interval. Figure 18 of Work Aid 2 illustrates representative current-time curves over a test period. The curves in Figure 18 show that good insulation exhibits a steady decrease in leakage current with time and that bad insulation exhibits a rise rather than a decline in leakage current. The polarization index can be calculated from this test data through division of the leakage current after one minute by the leakage current that is obtained after ten minutes. The Electrical Engineer should evaluate the dc high-pot test leakage current test data to ensure that the MCC high-pot test data meet the minimum requirements of a successful test. A polarization index value of less than two or dc high-pot test data curves that indicate a steady increase in leakage current over the duration of the test should be investigated by the Electrical Engineer who performs the test data evaluation.


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SYSTEM PRE-OPERATIONAL CHECK-OUT The system pre-operational checkout phase of the commissioning cycle for MCCs provides an opportunity for Saudi Aramco personnel to perform wiring checks, subsystem component check outs, and MCC component interlock tests. Each MCC controller, contactor, or starter component is checked to ensure that it works individually and as a complete system. Subsystems are checked to ensure that electrical continuity exists for control and protective devices. The proper operation of all subsystems is tested through use of controlled operation and check out of the controls and protective devices. Each subsystem is performance tested through the application of full operational voltage to each subsystem through the proper protective devices. A complete operational test is performed on equipment controls, interlocks, protective devices, and components with each subcircuit connected to its main system. During the performance test, the main systems are still isolated and independent from plant systems. Before the equipment is connected to the plant system, subsystem performance testing is critical to ensure the proper and safe operation of the equipment protection and control subsystems. Operation tests are performed to ensure that the various MCC operational interlocks function properly. For example, if an MCC cubicle door has a circuit breaker trip interlock, the trip interlock is tested. Circuit breaker trip tests are also conducted.


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SYSTEM OPERATIONAL CHECK-OUT The operational check-out phase of the commissioning cycle for MCCs provides an opportunity for Saudi Aramco personnel to perform the following: • Source feed compatibility checks • Complete MCC functional test Source feed compatibility checks are performed on MCCs through application of the full system voltage onto the MCC with all components (e.g., controllers) installed. With the voltage applied, voltage phasing, synchronizing, device rotation, protective relay calibration, and other source feed compatibility checks are performed. Parallel or alternate power source feed operations are also performed to ensure the total operation of the major components of the MCC. A complete system functional test is performed on MCCs to ensure that the entire low-voltage electric power distribution system functions in accordance with the system design. During the complete system functional test of MCCs, the electric distribution system is allowed to assume a fully loaded condition for a period of time that is adequate to obtain the maximum system temperature. After the loaded time period, MCC temperatures are monitored. MCC temperatures can be monitored locally through use of temperature monitoring equipment or through use of thermographic surveys. Temperature monitoring equipment can be temporarily installed at MCC vents or in the MCC itself. Particular attention should be paid to wiring and terminal connections during the complete system functional test.


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WORK AID 1:

REFERENCES FOR EVALUATING MOTOR CONTROL CENTERS UPON RECEIPT

Work Aid 1A:

MCC Applications Checklist

MCC rating information can be found on the equipment nameplate or in the manufacturer's technical manual. Use the following checklist and the appropriate sections of this Work Aid to verify that the type, the rating, and the operational characteristics of MCCs are correct for the application based on Saudi Aramco and industry standards. • Verify that the MCC low or medium voltage nameplate ratings are correct for the application. • Verify that the low voltage MCC switchgear meets the Saudi Aramco requirements that are shown in Figures 4 through 9. • Verify that the low voltage MCC matches the information that is provided in the data sheet (Figure 10). • Verify that the medium voltage MCC switchgear meets the Saudi Aramco requirements that are shown in Figures 11 through 16. Work Aid 1B:

Low Voltage MCC Ratings

This section of the Work Aid describes low voltage MCC ratings. For low voltage MCCs, the MCC bus capacity should be computed on the following basis: • 125% of the normal full-load current of the largest motor that is supplied by the MCC, plus • 100% of the full-load current of all other motors that can be operated at the same time, plus • 100% of all other loads (or a lower percentage if a diversity factor can be properly applied), plus • 20% allowance for future requirements. The final MCC bus capacity must be at least equal to the lesser of: • The continuous current rating of the main incoming circuit breaker. • The fan-cooled current rating of the power source transformer.


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The low voltage MCC short-circuit rating should not be less than 105% of the maximum available rms symmetrical current available at the MCC line terminals. The short-circuit interrupting rating must be a minimum of 22000 amperes of rms symmetrical current. Short circuits are to be computed as the sum of the short-circuit current contributions of the motors connected to the motor control center and all other short-circuit current contributions of the supply system at the point of connection to the motor control center. Work Aid 1C:

Low Voltage MCC Terminal Board Wiring

Because there are different terminal board arrangements in MCCs, NEMA ICS 2-322 provides for the different types of terminal board wiring that is required in accordance with the arrangement of the terminal boards. The different types of terminal board wiring are designated Type A, Type B, and Type C. The features that are required by NEMA ICS 2-322 for Type A, Type B, and Type C terminal board wiring are shown in Figure 4.

Type A (Class I Only) Type B

Type C

(a) Terminal boards for load or control connections are prohibited. (b) Connection diagrams are used only for each combination controller or control assembly. (c) Sketches of the overall dimensions of the control centers are required. (a) A unit control terminal board must be provided. Unit load terminal blocks must also be provided for combination controllers that are Size 3 or smaller. These terminal boards must be mounted on, or adjacent to, each unit. (b) Sketches of the overall dimensions of the control centers are required. (c) (Class I Only). Connection diagrams are used only for each combination controller or control assembly. (d) (Class II Only). The necessary interconnecting wiring between combination controllers and control assemblies must be in the same MCC section. (e) (Class II Only). A connection diagram of the complete control assembly is required. (a) Master section terminal boards must be present that include load terminals for combination controllers that are Size 3 or smaller. All control terminals for all combination controllers or control assemblies in each vertical section must be mounted on the stationary structure. Load terminal boards for feeder tap units are prohibited. Figure 4: Low Voltage MCC Terminal Board Wiring Type Features (From NEMA ICS 2-322)


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Type C (Cont'd)

(b) Sketches of the overall dimensions of the control centers are required. (c) (Class I Only). Wiring between sections or between master terminals is prohibited. (d) (Class I Only). Interconnections between any combination controllers or control assemblies are prohibited. All outgoing wires from any unit must be carried to the master terminal board, except wiring for combination controllers that are Size 4 or larger. (e) (Class I Only). Connection diagrams for each combination controller or control assembly are required. (f) (Class I Only). A sketch of main terminal boards showing general location of terminals is required. (g) (Class II Only). The necessary interconnecting wiring between combination controller and control assemblies must be in the same section. (h) (Class II Only). A connection diagram of the complete control center is required. Figure 4: Low Voltage MCC Terminal Board Wiring Type Features (From NEMA ICS 2-322) (Cont'd)

Work Aid 1D:

Minimum Low Voltage Indoor Motor Control Center Technical Requirements

The minimum technical requirements for low voltage indoor motor control centers (MCCs) are defined in 16-SAMSS-503. Low voltage in Saudi Aramco installations is defined as 600 V and below. The requirements of 16-SAMSS-503 apply to full-voltage combination starters, feeder circuit breakers, contactors, dry-type transformers, panelboards, and auxiliary equipment that are assembled into MCCs and switchracks; however, only the MCC information will be presented in this section of the Work Aid.


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Figure 5 shows Saudi Aramco low voltage indoor MCC general requirements from 16-SAMSS503.

General Requirements

MCCs must be suitable for operation at nameplate rating within an ambient air temperature range of 0 oC to 40 oC. MCCs must conform to the requirements of NEMA ICS 2-322, except as otherwise indicated in 16-SAMSS-503. Designs and materials that are used in control assemblies must have at least two years of verifiable proven field service. The Vendor must supply a Users List indicating User company name, installation site, date of installation, and equipment characteristics that are similar to the equipment that is quoted.

Figure 5: Saudi Aramco Low Voltage MCC General Requirements (From 16-SAMSS-503)


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Figure 6 shows Saudi Aramco low voltage MCC construction requirements from 16-SAMSS503. General Construction Requirements

Minimum MCC Construction and Design Requirements

An external indication (e.g., "ON" or "OFF") must be provided to show the circuit breaker or disconnect switch position. Motor control assemblies must be "fully-rated" for bracing and interruption of the available short circuit current that is indicated on the Engineering Drawings and/or the Data Schedule. No operating device or instrument can be more than 1980 millimeters (78 inches) above the floor. Motor data that is required for the selection of the controller and motor control components must be as shown on the Engineering Drawings. All devices that are supplied under this specification that are to be used in hazardous (electrically classified) locations must be housed in enclosures that are approved for the purpose. Arcing devices must be housed in certified explosion proof enclosures. Sealing fittings must be furnished as required. Oil-immersed equipment (NEMA Type 8) is not acceptable. MCCs must be rigid, free-standing, metal-enclosed structures, that consist of vertical sections assembled into a group that have a common power bus and that form an enclosure to which additional sections may readily be added. Each MCC vertical section must be subdivided into compartments that contain the various control and protective devices. MCC cubicle design must be NEMA Class I, Type B. All ventilation openings must be suitably filtered or screened with a specified corrosion-resistant material (such as stainless steel hardware cloth or galvanized screen) that is arranged to prevent the entrance of rodents and other foreign matter.

Figure 6: Saudi Aramco Low Voltage MCC Construction Requirements (From 16-SAMSS-503)


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Minimum MCC Construction and Design Requirements (Cont'd)

All control devices must be selected for proper operation in the designated atmosphere without further protection. Structure drilling, tapping, cutting, welding, and forming must be designed and factory finished to permit field rearrangement of the controller compartments into any possible combination by the use of simple fasteners such as bolts and screws. If the bus plug-in contact design uses special shapes or fittings that are connected permanently to the bus, the shapes or fittings must be provided at all locations that are needed by any rearrangement of all possible size compartments. Control device assemblies must have plug-in line connections or must be arranged so the assembly can be removed without deenergizing the MCC. Fuses must be accessible for replacement without removing the control device assembly from the MCC or disconnecting cables. Units that are designated as "FUTURE" on the Engineering Drawings must be complete with stationary elements, drawout pans, and door. A means must be provided to cover the openings which expose the vertical bus. Adequate space must be provided for incoming power, control, ground conductors, and conduit terminations. Minimum bending radius restrictions must be followed. Provisions for terminating all incoming conductors must be included. The line side of incomers must be provided with an ammeter and voltmeter, together with associated current and potential transformers.

Figure 6: Saudi Aramco Low Voltage MCC Construction Requirements (From 16-SAMSS-503) (Cont'd)


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Figure 7 shows Saudi Aramco low voltage MCC enclosure and isolating panel requirements from 16-SAMSS-503.

MCC Enclosure Requirements

Isolating panels

Enclosures must be suitable for back-to-wall or back-to-back mounting. Back-to-back constructions that have a common horizontal bus are not acceptable. Enclosures must be designed for front access only and must be provided with floor channels. Enclosures must have floor plates with holes and grommets as specified on the Data Schedule. Holes must be provided with cover plates. Vertical sections must have a minimum width and depth of 508 mm (20 in), with each vertical section having a vertical wiring compartment with hinged covers, means for support of wiring, and grommets where wiring penetrates metal barriers. Space for horizontal wiring between vertical sections at the top and bottom must be provided. Wiring spaces must be isolated from the buses. Minimum individual space allocation in vertical sections of motor starters must be sufficient to accommodate a NEMA Size 2 controller. All hardware must be galvanized cadmium or chromium-plated mild steel or stainless steel. Isolating panels must be provided between device, bus, and cable compartments to permit the cables to be pulled safely into the MCC and extend to device compartments with the control center energized. Uninsulated live parts must not be located in cable pulling spaces. Isolating panels must be provided between device, bus, and cable compartment to permit personnel to work safely. Safe work is performed within either an empty compartment or a compartment from which the control assembly has been removed while the bus is energized. The isolating panels must prevent transmission of arcs and must retard the migration of arc products into bus spaces and/or cable pulling spaces. The isolating panels must prevent transmission of arcs and retard the migration of arc products between device compartments even when an intervening device assembly has been removed. Figure 7: Saudi Aramco Low Voltage MCC Enclosure and Isolating Panel Requirements (From 16-SAMSS-503)


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Figure 8 shows Saudi Aramco low voltage MCC bus and space heater requirements from 16SAMSS-503.

Bus Requirements

Main horizontal buses must consist of electrical grade copper bus bars that are mounted on glass-reinforced polyester or non- hygroscopic ceramic insulators. Buses must be rated for a minimum continuous current rating of 600 A, braced for a minimum of 42,000 A symmetrical short circuit current. All bus connections must be bolted with all bar connecting surfaces silver-plated or tin-plated. Power bus bars, bar connections and plug-in connection continuous current ratings must be based on a 40 oC ambient temperature and 50 oC temperature rise. Bus phase arrangement must be 1- 2- 3, counting from front to back, top to bottom, or left to right, as viewed from the front of the control assembly. MCCs must have a silver plated or tin plated bolted copper bar ground bus that is horizontally mounted near the bottom of the structure and that extends throughout the length of the MCC. Cable is not an acceptable substitute for bus material. Connectors that are sized for 70 square millimeters (No. 2/0 American Wire Gage (AWG)) copper grounding conductor must be provided on each end of the bus. The minimum momentary rating of all phase, neutral, and ground buses must be 42,000 RMS symmetrical amperes. The continuous current rating of neutral buses, where specified, must be 50 percent of the bus phase rating. Figure 8: Saudi Aramco Low Voltage MCC Bus and Space Heater Requirements (From 16-SAMSS-503)


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Vertical power buses must be copper, must have a minimum continuous current rating of 600 A, and must be enclosed in a flame-retardant, non-tracking, low-hygroscopic, glass-reinforced, polyester insulation and bus support system. The bus support system must provide phase-to-phase and phase-to-ground bus isolation. Cable is not acceptable as a substitute for copper bar, including the transition busing to other equipment. Space Heaters Space heaters must be provided in each MCC vertical section. Space heater heating elements must have a voltage rating of approximately twice the supply voltage. Heaters and associated circuits must be rated for continuous duty. A space heater control system must be furnished for each piece of vertical equipment and must consist of a thermostat that is used to control the heater so that the equipment interior temperature is maintained several degrees above the ambient temperature. The space heater system must be completely wired and must include a manual disconnect. Space heater sheath temperature for all equipment must be limited to the temperature that is specified on the Data Schedule. Bus Requirements (Cont'd)

Figure 8: Saudi Aramco Low Voltage MCC Bus and Space Heater Requirements (From 16-SAMSS-503) (Cont'd)


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Figure 9 shows Saudi Aramco low voltage MCC nameplates, wiring, and miscellaneous equipment requirements from 16-SAMSS-503.

Nameplates

Engraved phenolic nameplates that show black letters on white face must be provided and attached with stainless steel or brass screws to the door of each MCC unit. Warning nameplates must be provided on each compartment for which opening of the branch circuit breaker does not de-energize all voltage sources within the unit. The warning plate must have white characters on a red background that read: "CAUTION - THIS UNIT CONTAINS AN EXTERNAL VOLTAGE SOURCE!". A nameplate must be attached to each controller and must indicate manufacture's catalog designation, maximum horsepower rating at a specified voltage, maximum continuous amperes, and control circuit voltage. All nameplate wording must be in the English language according to American usage except for danger and warning indicators which must be written in both Arabic (Naskh script) and English. White characters on a red background must be used. Separate nameplates, suitably located, must indicate the following: 1) Warning or operational instructions as required. 2) Identity of all relays, meters, etc. 3) Purchaser's assigned motor or equipment number and identification, when specified. The bus structure, each motor control unit, and each feeder tap unit must be identified with its short-circuit current rating expressed in RMS symmetrical amperes. This identification supersedes any interrupting rating shown on fuses or circuit breakers that are included in the units.

Figure 9: Saudi Aramco Low Voltage MCC Nameplates, Wiring, and Miscellaneous Equipment Requirements (From 16-SAMSS-503)


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Wiring

Miscellaneous Equipment

Control and secondary conductors must be stranded copper, 600 V, NEC Type SIS or THHN. The minimum conductor size must be 2.5 square mm (No. 14 AWG). Insulated, ring tongue, compression (crimped) terminals must be provided for all control and secondary wiring terminations. All connection points between assembly control devices and field wiring must be made with terminal blocks. Terminal blocks must be one-piece, phenolic, barrier-type, rated 20 A, 600 V, minimum, with pre-numbered marking strips. A maximum of two wires per point is permitted. Two-piece terminal blocks which allow complete withdrawal of unit assemblies are acceptable. Shorting terminal blocks must be provided for current transformer circuits. Each wire must be identified with a thermoplastic, slip-on type (ferrule), marker with permanently printed characters. Snap-on or adhesive type markers are prohibited. Pushbutton and selector switches must be of the heavy-duty oil-tight type rated 10 A continuous at 600 V. Indicating lights must be of the incandescent heavy-duty oil-tight type with integral transformer or series voltage-dropping resistor sized so that the applied voltage is 80 percent of rated lamp voltage. Indicating lights must be designed so that relamping is performed from the front of the MCC. All special tools required, such as nonstandard wrenches, sockets, etc., used to latch/unlatch, bolt/unbolt, equipment supplied under this specification, must be provided with each MCC assembly.

Figure 9: Saudi Aramco Low Voltage MCC Nameplates, Wiring, and Miscellaneous Equipment Requirements (From 16-SAMSS-503) (Cont'd)

Figure 10 shows the data schedule that is used to order low voltage switchracks and MCCs from the manufacturer.


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DATA SCHEDULE FOR 16-SAMSS-503, LOW-VOLTAGE SWITCHRACKS (600 VOLTS AND BELOW) INFORMATION SUPPLIED BY BUYER 1.

Buyer's Quotation Request/Purchase Order No. ________________________

2.

Buyer's B.I./J.O. No. _____________________________________________

3.

Buyer's Line Item No. _____________________________________________

4.

Area Classification: ( ) Classified ( ) Unclassified Class ______ Group(s) ______ Division ___

5.

Enclosure Type: ( ) NEMA Type 4, 7 ( ) NEMA Type 4 ( ) Other ___________________ (Specify)

6.

Main Horizontal Bus Continuous Rating ___________ A (RMS) at: ( )50 deg C, (Covered) ( )70 deg C, (Uncovered)

7.

Incoming Section Entry: ( ) Top, ( ) Bottom No. of Access holes: ____________

8.

Space Heater Supply; Voltage: __________________ V AC Source: ( ) Buyer ( ) Vendor CPT Maximum Surface Temperature of Heater Element deg C __________________

9.

Canopy ( ) No ( ) Yes; Canopy Lighting ( ) Yes ( ) No

10.

Enclosure Mounting and Arrangement: ( ) Single-Row ( ) Double-Row ( ) Front ( ) Back ( ) Front and Back

11.

Incoming Feeder: ( ) Bus Duct ( ) Cable in Conduit

12.

Size of Incoming Feeder: __________________

13.

Cable Conductors per Phase: _______________

14.

Control Power Voltage: ____________________ Approved: _____________________ Dwg. No. NT- __________________ Date: _____________________

Revision No. __________________

Sheet 1 of 1

Figure 10: Data Schedule for Low Voltage Switchracks and MCCs (From 16-SAMSS-503) Saudi Aramco DeskTop Standards

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Work Aid 1E:

Medium Voltage MCC Ratings

Figure 11 shows medium voltage controller ratings.

1 Controllers that are rated for 630 amperes continuous are available from some manufacturers with interrupting ratings up to 500 MVA at 4000 volts. * Not extracted from NEMA standards.

Figure 11: Ratings for Class E2 (Fused) Medium Voltage Motor Controllers (From SADP-P-116 and NEMA ICS 2-324)

The required interrupting capacity must be 350 MVA at 4800 volts.


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Work Aid 1F:

Medium Voltage MCC Requirements

The minimum technical requirements for medium-voltage (5 kV class), metal-enclosed indoor MCCs are described in 16-SAMSS-506. The requirements of 16-SAMSS-506 apply to National Electrical Manufacturers Association (NEMA) Class E-2 current-limiting fused controllers and all control and auxiliary equipment that is assembled into MCCs. Figure 12 shows Saudi Aramco medium voltage indoor MCC general requirements from 16SAMSS-506.

General Requirements

Oil-immersed controllers are not acceptable for use in Saudi Aramco installations. Motor control assemblies must be suitable for continuous operation at nameplate rating with cooling air surrounding the assembly enclosure within the limits of 0oC and 40oC. Designs and materials used in the control assemblies must have at least two years of verifiable proven field service. The Vendor must supply a Users List indicating User company name, installation site, date of installation, and equipment characteristics similar to equipment quoted.

Figure 12: Saudi Aramco Medium Voltage MCC General Requirements (From 16-SAMSS-506)

Figure 13 shows general construction and design requirements for medium voltage MCCs.


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General Construction Requirements

Minimum MCC Construction and Design Requirements

Controllers must be of the metal enclosed type consisting of a free-standing, full-height structure with a maximum of two controllers per vertical section. Enclosures must be rigidly constructed to allow mounting pad level variations of +/- 1/8 inch. Under these conditions, doors must open and close smoothly and all mechanical interlocks must function properly. Enclosures must be 2.28 m (90 in) nominal height. If Vendor's standard is three-high construction, the top unit must be for "FUTURE" or for auxiliary devices, as indicated on Engineering Drawings. Grounded metal barriers must be provided to isolate each vertical section, each compartment within a vertical section, high and low voltage compartments, and main horizontal power bus compartment. A corrosion-resistant coating over a suitably prepared surface must be applied to the inside and outside of the cubicle. Isolating shutters must be provided to automatically cover vertical bus when a drawout component is moved to the withdrawn position on "FUTURE" as well as active compartments. All parts must be readily accessible for maintenance and inspection. Power fuses and contactor must be mounted on a single drawout carriage assembly. The cubicle design must be NEMA Type 1 for installation in an environmentally controlled location. All ventilation openings must be suitably filtered or screened with stainless steel hardware cloth arranged to prevent the entrance of rodents.

Figure 13: Saudi Aramco Medium Voltage MCC Construction and Design (From 16-SAMSS-506)


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Minimum MCC Construction and Design Requirements (Cont'd)

All control devices must be selected for proper operation in the designated atmosphere without further protection. Enclosures must conform to NEMA ICS 6 "Enclosures for Industrial Controls and Systems" requirements for NEMA Type 1. Enclosures must be of carbon steel sheet metal with supporting frame, designed for front access only, and suitable for back-to-wall or back-to-back mounting. Hinged and removable panels and doors must be provided with captive hardware. Self-tapping screws are not acceptable. All unpainted hardware must be galvanized, stainless steel, or cadmium or chromium plated. Compartment doors must be double or full-length hinged.

Figure 13: Saudi Aramco Medium Voltage MCC Construction and Design Requirements (From 16-SAMSS-506) (Cont'd)

Figure 14 shows Saudi Aramco medium voltage MCC enclosure and isolating panel requirements from 16-SAMSS-506.

MCC Enclosure Requirements

Enclosures must conform to NEMA ICS 6 "Enclosures for Industrial Controls and Systems" requirements for NEMA Type 1. Enclosures must be of carbon steel sheet metal with supporting frame, designed for front access only, and suitable for back-to-wall or back-to-back mounting. Hinged and removable panels and doors must be provided with captive hardware. Self-tapping screws are not acceptable. All unpainted hardware must be galvanized, stainless steel, or cadmium or chromium plated. Compartment doors must be double or full-length hinged. Figure 14: Saudi Aramco Medium Voltage MCC Enclosure and Isolating Panel Requirements (From 16-SAMSS-506)


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Figure 15 shows Saudi Aramco medium voltage MCC bus and space heater requirements from 16-SAMSS-506.

Bus Requirements

The entire length of the power bus must be individually insulated for rated voltage. Full height single units must be equipped with power bus bars and a wiring trough extending the full cubicle width. All power, ground, and wiring facilities must be arranged to facilitate future additions. All power and ground buses, including transition busing to other equipment, must be constructed of bar material. Cable is not acceptable for power or ground busing. Power and ground buses must be full size and continuous throughout. Tapered bus sizing is prohibited. Bolted power bus connections must be provided with a minimum of 2 bolts, nuts, and with either dished (conical) spring washers or flat washers and split lockwashers. Bus bar connection surfaces must be silver-plated or tin-plated. Power bus insulation materials for bars and bar connections must be flame-retardant, low-hygroscopic, and track-resistant throughout. Bolted bus joints must be covered with removable insulating boots. Taping of bus and bolted joints is not acceptable. Bus phase arrangement must be 1, 2, 3, counting from front-to-back, top-to-bottom, or left-to-right, as viewed from the main switching device operating mechanism side. Space Heaters Each vertical section must contain a thermostatically controlled space heater. Heating elements must have a voltage rating of approximately twice the supply voltage for extended service life. Heaters and associated circuits must be rated for continuous duty. Each heater circuit must be provided with an externally operable thermal-magnetic molded-case circuit breaker to serve as a disconnecting and overcurrent protection device. Figure 15: Saudi Aramco Medium Voltage MCC Bus and Space Heater Requirements (From 16-SAMSS-506)


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Figure 16 shows Saudi Aramco Medium voltage MCC nameplates, wiring, and miscellaneous equipment requirements from 16-SAMSS-506.

Nameplates

Nameplates must be attached to the controller group, individual doors, or contactor as appropriate and must indicate the following: 1. Manufacturer's shop order number, date, and catalog designation. 2. Horsepower rating of motor. 3. Interrupting rating of the controller. 4. Maximum continuous amperes. 5. Nominal voltage rating. 6. Control circuit voltage. Separate nameplates suitably located must indicate: 1. Warning of operational instructions as required. 2. Identity of all relays, meters, and so forth. 3. Purchaser's assigned motor number if specified. 4. Foreign voltage when external sources are used. Device nameplates must be provided for the identification of each controller and auxiliary unit, indicating the circuit number and load served or equipment contained within an auxiliary cubicle. All panel mounted devices must be identified by escutcheon or nameplate on the front of the panel and by nameplate on the rear of the panel adjacent to the device terminals. Protective relay nameplates must be provided to indicate protective function, ANSI device number, and phase(s) which is/are monitored. Device nameplates must be engraved laminated plastic with black 6.4 mm (0.25 in) characters on a white 64 mm (2.5 in) by 25 mm (1 in) background as a minimum. Device nameplates must be in the English language according to American usage.

Figure 16: Saudi Aramco Medium Voltage MCC Nameplates, Wiring, and Miscellaneous Equipment Requirements (From 16-SAMSS-506)


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Nameplates (Cont'd)

Wiring

Miscellaneous Equipment

Warning plates must be provided on each compartment door in which an external voltage source is terminated, reading: "CAUTION -THIS UNIT CONTAINS AN EXTERNAL VOLTAGE SOURCE." Auxiliary cubicles containing drawout or tilt-out potential transformers supplying undervoltage relays must be provided with a warning nameplate reading: "CAUTION - OPENING THIS COMPARTMENT TRIPS UNDERVOLTAGE RELAYS." Manual trip devices must be labelled: "Manual/Emergency Trip". Warning nameplates must be engraved laminated plastic with white characters on a red background. Warning nameplates must be written in both Arabic and English. Nameplates must be attached with stainless steel or brass screws except that nameplates inside compartment may be attached with permanent adhesives. Control and secondary conductors must be stranded copper 600 V NEC Type SIS or THHN. Minimum conductor size must be 2.5 sq mm (14 AWG). Each wire must be identified with a thermoplastic, slip-on wire marker with permanently printed characters. Snap-on and adhesive type markers are prohibited. All connection points between assembly control devices and field wiring must be made with terminal blocks conforming to the requirements of 16SAMSS-506. All connections between compartment control wiring and removable assembly (truck) mounted devices must be by a single, self-aligning, multi-contact, stab assembly. (When a stab assembly cannot be used, a potted connector assembly must be used in the wiring harness.) Each controller must have both externally and internally operable control devices.

Figure 16: Saudi Aramco Medium Voltage MCC Nameplates, Wiring, and Miscellaneous Equipment Requirements (From 16-SAMSS-506) (Cont'd)


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Miscellaneous Equipment (Cont'd)

Pushbutton and selector switches must be of the heavy-duty oil-tight type rated 10 A continuous at 600 V. Pushbutton control switches must be constructed to prevent accidental actuation. Externally operable control devices must be of the hand-reset type for both the overload relays and lockout relays. An externally operable alternating current control circuit power switch must be provided to be used as a control power disconnect and as a maintained stop for both magnetically held and latched contactors. Internally operable control devices must include a readily accessible start/stop pushbutton to operate the main contactor for maintenance testing. This device must be operable when the controller is in the test position. An ammeter with a transfer switch and red and green "RUNNING" and "STOPPED" indicating lights must be mounted clearly visibly on the outermost cubicle door. The red and green indicating lights must be supplied directly from "M" auxiliary contacts. Hand-reset lockout relay operating coil circuit must be monitored by a white indicating light located adjacent to the relay handle. For motor feeders, an ammeter for motor space heaters must be mounted clearly visible on the outermost cubicle door. Indicating lights must be of the incandescent heavy-duty oil-tight type with integral transformer or series voltage-dropping resistor sized so that the applied voltage is 80 percent of rated lamp voltage. Indicating lights must be designed so that relamping is performed from the front of the MCC. All special tools required, such as nonstandard wrenches, sockets, etc., used to latch/unlatch, bolt/unbolt, equipment supplied under this specification, must be provided with each MCC assembly.

Figure 16: Saudi Aramco Medium Voltage MCC Nameplates, Wiring, and Miscellaneous Equipment Requirements (From 16-SAMSS-506) (Cont'd)


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WORK AID 2:

REFERENCES FOR EVALUATING MOTOR CONTROL CENTER INSTALLATION AND TESTING

Work Aid 2A:

MCC Commissioning Electrical Test Values

1.

Insulation resistance must not be less the fifty megohms. a.

Megger test voltages must be 1000 V dc in accordance with Saudi Aramco PreCommissioning form P-000, Testing Guide Lines.

b.

The insulation resistance (megger) test values must be greater than the manufacturer's minimum value. If the manufacturer's minimum value is not provided, the value of the insulation resistance should be greater than the rated voltage + 1 kV in megohms. For example, a 600 V rated system must have a measured insulation resistance that is greater than 1.6 megohms.

c.

Do not megger solid state devices.

2.

Contact resistance must be determine in microohms or millivolts. Values of contact resistance in excess of 200 microohms and deviations of more than +/-20% must be investigated. Technical data to evaluate the results of the contact resistance test can be found in the circuit breaker manufacturer's technical manual or in the Saudi Aramco PreCommissioning form, P-000, Testing Guide Lines.

3.

A dc high-potential test is one in which the increase of applied voltage is controlled. Measured currents are continuously observed for abnormalities with the intention of stopping the test before breakdown occurs. The voltage that is used for the dc high-pot test should be in accordance with the manufacturer's technical manual for the MCC. If a manufacturer's technical manual is not available, then the Saudi Aramco PreCommissioning Form, P-000, Testing Guide Lines, must be used. In accordance with P000, the high-pot test voltage is 9 kV for equipment that is rated 2.5 kV. The dc high-pot test is conducted in two stages as follows: a.

A polarization index (PI) test is performed by applying an initial voltage step of about one-third of the recommended maximum voltage. The initial voltage step must be maintained at a constant level for 10 minutes. The PI is calculated by dividing the one minute leakage current by the 10 minute leakage current. A PI value of 2.0 or less must be investigated.

b.

After the initial 10 minute test, the dc test voltage is increased in approximately 10 uniform steps. Each step should have a one minute duration. The voltage is increased until the maximum recommended dc value is reached.


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4.

Minimum pickup current, trip times, and instantaneous pickup values of protective equipment (e.g., relays) must be adjusted to engineer settings. Test values should fall within manufacturer's published time-current characteristic tolerance band.

Work Aid 2B:

Information, Formulas, and Tables for Use in Evaluating the Results of Insulation Resistance (Megger) Tests

The results of all commissioning megger tests that are performed must be documented on the appropriate Saudi Aramco pre-commissioning form. The following are the types of megger tests that can be conducted: • Short time or spot reading • Time resistance • Dielectric absorption ratio When the dielectric absorption ratio megger test is performed, the polarization index can be determined through use of the following equation: Figure 17 provides insulation conditions for 60/30 second ratio results and for 10/1 minute ratio results.

Figure 17: Dielectric Absorption Ratio Chart


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Work Aid 2C:

Information, Formulas, and Tables for Use in Evaluating the Results of DC Hi-Pot Tests

The dc hi-pot test should be secured if one of the following situation occurs: • The duration of the test has expired. • A rapid rise in leakage current occurs. • The polarization index < 1. The following are the characteristics of a satisfactory dc hi-pot test: • The leakage current gets smaller over time. • The polarization index > 1. • The leakage current increases on a straight line as voltage is increased. No "knee" is noticeable in the leakage current curve. An example of dc hi-pot test data is shown in Figure 18. Figure 18 also shows both good and bad insulation test data.

Figure 18: Example of DC Hi-Pot Test (Good and Bad Insulation) Saudi Aramco DeskTop Standards

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Work Aid 2D:

Saudi Aramco Pre-Commissioning Form

Figures 19 shows the Saudi Aramco Pre-Commissioning Form, P-018, Motor Control Centers, which provides a field installation checklist for MCC installations. The pre-commissioning form has a broad checklist of visual and mechanical inspections, as well as the listed electrical and tests that are required for MCC installations. Space is also provided on the form for test data.


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Figure 19: Saudi Aramco Pre-Commissioning Form, P-018, Motor Control Centers Saudi Aramco DeskTop Standards

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Figure 19: Saudi Aramco Pre-Commissioning Form, P-018, Motor Control Centers (Cont'd) Saudi Aramco DeskTop Standards

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Work Aid 2E:

Excerpts from GI 2.710

The following is an excerpt from GI 2.710, New Construction Check List Example, that illustrates the overall checklist and sign-off for major pieces of electrical equipment. 3.

Electrical Equipment All substations, power cable, electrical equipment, Construction Agency including lighting and wiring, to be checked for proper application, operation, and grounds. Distribution panels, switches properly identified, and all energization certificate requests signed.

Power Distribution Dept.

Project Inspection

Commissioning (Note 1) Figure 20 shows an excerpt from GI 2.710, General Instruction Manual, that illustrates the inspections and tests that should be performed on major pieces of electrical equipment prior to the turnover of a facility.


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Figure 20: GI 2.710 Excerpt


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Figure 20: GI 2.710 Excerpt (Cont'd)


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Figure 20: GI 2.710 Excerpt (Cont'd)


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GLOSSARY dielectric absorption ratio

The ratio of two timed insulation resistance readings (such as a 60-second reading that is divided by a 30-second reading).

polarization index

The ratio is a ten-minute insulation resistance reading that is divided by a one-minute insulation resistance reading.


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Commissioning Motor Control Centers

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