Power System Control
Status of SCADA System in Pakistan
Submitted to: Prof: Dr. Azam-ul-Asar
[email protected]
Submitted by: Engr. Muhammad Zafran 1st Semester MSc. Electrical Power Engineering
[email protected]
Department of Electrical Engineering N-W.F.P, University of Engineering & Technology Peshawar, Pakistan 1
CONTENTS LIST OF FIGURES…………………………………………………….... 3 LIST OF TABLES…………………………………………………….....
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NOMENCLATURE……………………………………………………..
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ACKNOWLEDGEMENTS……………………………………………... 6 ABSTRACT……………………………………………………………..
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1 SCADA………………………………………………………… 8 1.1 Introduction.......................................................................................
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1.2 Power System Automation…………………………………………
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2 Status of SCADA System in Pakistan………………………………. 9 2.1 National Power Control Centre……………………………………..
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2.2 SCADA System for National Power Control Centre ……………… 10 2.2.1
Data Acquisition System…………………………………. 10
2.2.2
SCADA(NPCC) Communication Medias………………... 11
2.2.3
Computer Systems used by SCADA (NPCC)……………. 13
2.2.4
Remote Terminal Units…………………………………... 14
2.3 Miscellaneous information about SCADA(NPCC)………………... 16 2.3.1
Data Acquisition facilities………………………………... 16
2.3.2
Remote Control facilities…………………………………. 17
2.3.3
Display types…………………………………………….... 17
2.3.4
Storage capacities………………………………………… 17
3 Suggestions for improvement in status of Present SCADA system. 18 3.1 SCADA Hardware…………………………………………………. 18 3.2 SCADA Software………………………………………………….. 19 3.3 Remote Terminal Units……………………………………………. 19 3.4 Telecommunications………………………………………………. 20 REFERENCES…………………………………………………………
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LIST OF FIGURES
Figure-1:
SCADA System………………...……………………..………...
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Figure-2:
Data Acquisition System………………......................................
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Figure-3:
Data Transmission Channels/Medias…….………………….......
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Figure-4:
Network Configurations.………………………………………...
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Figure-5:
RTU Major Elements……………………………………………
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LIST OF TABLES
Table-1:
Status of Installed RTUs………………………………………...
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Table-2:
SCADA Hardware……………………………………………...
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Table-3:
SCADA Software……….………………………………….......
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Table-4:
Remote Terminal Units…..…..…………………………………
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Table-5:
Telecommunications……………………………………………
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NOMENCLATURE Most of the reoccurring abbreviations and symbols are described here.
Abbreviations
SCADA
Supervisory Control And Data Acquisition
RTU
Remote Terminal Unit
AGC
Automatic Generation Control
NPCC
National Power Control Centre
RCC
Regional Control Centre
IPP
Independent Power Plants
VHF
Very High Frequency
UHF
Ultra High Frequency
RAM
Random Access Memory
ROM
Read Only Memory
PLC
Programable Logic Control
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ACKNOWLEDGMENTS
First and foremost, I would like to thank Almighty Allah for blessing me with the strength, intelligence, and patience to complete this task.
Then I would like to thank, Sir. Dr. Azzam-ul-asar, for his friendly behavior and help all the time.
Finally, I am very indebted to Engr. Shahrukh Salim (Jr. Engineer, NTDC Islamabad) for his support and also very grateful to National Power Control Centre team for providing material related to my work.
Muhammad Zafran 1st Semester MSc. Electrical Power Engineering
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ABSTRACT
Status of SCADA System in Pakistan describes the present status of Supervisory Control And Data Acquisition System in Pakistan. Status of different components of SCADA System at National Power Control Centre and Power station like, Remote Terminal Units, Computer Systems, Communication Channels, Data Acquisition, etc are discussed. Its working is briefly explained. Different problems in present status of SCADA system are also identified and suggestions are also provided for improving and upgrading its operation and status.
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Status of SCADA System in Pakistan 1. SCADA 1.1. Introduction The ability to perform operations at an unattended location from an attended station or operating center and to have a definite indication that the operations have been successfully carried out can provide significant cost saving in the operation of a power system. This is exactly what we try to achieve through the SCADA (an acronym for Supervisory Control and Data Acquisition) system. A formal definition of SCADA system, as recommended by IEEE, is “A collection of equipment that will provide an operator at a remote location with sufficient information to determine the status of particular equipment or a process and cause actions to take place regarding that equipment or process without being physically present”. Power system vendors are following a trend to make devices smarter so they can create and communicate the required information [1]. The main purposes for the use of a SCADA system would be to collect the needed data from remote sites and even the local site, displaying them on the monitor of the master computer in the control room, storing the appropriate data to the hard drive of the master computer and allowing the control of field devices (remote or local) from the control room.
Figure-1: SCADA System
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1.2. Power System Automation A power system consists of devices that generate, transmit, and distribute power. Power system automation is the act of automatically controlling the power system via automated processes within computers and intelligent I&C devices. It consists of three major processes, namely, data acquisition, power system supervision and power System control all working in a coordinated automatic fashion. Data acquisition refers to collecting data in the form of measured analog current or voltages values or the open or closed status of contact points. Power system supervision is carried out by operators and maintenance engineers through this acquired data either at a remote site represented by computer displays and graphically wall displays or locally, at the device site, in the form of front-panel displays and laptop computers. Control refers to sending command messages to a device to operate the I&C (A collection of devices that monitor, control and protect the system is referred as instrumentation and control (I&C) system) and power system devices [2, 3, 4].
2. Status of SCADA System in Pakistan [5] 2.1. National Power Control Centre The National Power Control Centre located in Islamabad was inaugurated by Mr. Ghulam Ishaq Khan, President of Pakistan on 20th January, 1990. It envisages implementation of the modern computerized load dispatch facilities for operating WAPDA's power system, by setting up of one National Power Control Centre (NPCC) at Islamabad and two Regional Control Centre at Islamabad and Jamshoro for northern and southern parts of the network respectively. The main functions of these Power Control Centre are given below: 1. Real time control of the load generation, power exchanges, voltage regulation, generation reserves and the transmission network. 2. Follow up of efficiency, fault analysis, compilation of statistics, reporting and accounting. 3. Short and long term planning, including load prediction, and generators, schedules, power balance planning, coordination of unit out-ages for maintenance and planning for reserves. 4. Arranging of routine and emergent short downs on generators, transmission lines, power transformers and other components of the power system. Above functions are to be performed by the Power Control System with the help of hitech computers and other modern facilities for power supervisory control, data
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acquisition and energy management. Under this project all 500 KV, 220 KV and some of the important 132 KV grid stations have been connected to the SCADA (Supervisory Control and Data Acquisition) system.
2.2. SCADA System for National Power Control Centre Present status of SCADA system at NPCC, its components, and its working etc. is given below:
2.2.1 Data acquisition system Data acquisition in SCADA used to access and control information or data from the equipment being controlled and monitored. The data accessed are then forwarded onto a telemetry system ready for transfer to the different sites. They can be analog and digital information gathered by sensors, such as flow meter, ammeter, etc. It can also be data to control equipment such as actuators, relays, valves, motors, etc. SCADA computers at NPCC regularly monitor the complete status of power system through Remote Terminal Units (RTUs), located at each power system. Whole process can be simplified through below Figure-2:
Main Computer System
Front End
Remote Terminal Units
Power Plant
Figure-2: Data Acquisition System
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2.2.2. SCADA (NPCC) Communication Medias Communication is of primary importance for a SCADA system at NPCC. Poor communication results in errors or lost messages. A system cannot function properly without reliable and adequate communication channels. NPCC uses the various communication systems media; ranging from satellite, to microwave, to fiber optic, PTCL, Mobile and to cable TV circuits. Figure-3 is depicting the various channels used by SCADA (NPCC).
Figure-3: Data Transmission Channels/Medias
Network Configurations Communication Network for local SCADA can be a combination of any of the following:
Leased lines Dial up lines Cellular circuits or VHF-UHF radio.
Leased lines are reliable & require less initial investment in equipment. It is used when data polled from the remote sites is required at the control station continuously in real time. The dial up lines are used when the information at the remote sites are required
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less often. The investment in equipment is low. The modems used are the same as those used with personal computers. The cellular circuits are similar to the dial-up except special modems & telephones are required at the remote sites (to be connected to the RTUs). VHF-UHF radio requires a transmitter-receiver & antenna for each site. Distances are limited to line-of-site from antenna to antenna. Repeaters may be required depending on the range and the attenuation level. The range is function of RF power (2 to 5 watts for narrow band & 1 watt for spread spectrum), the receiver sensitivity, the frequency selected. The 3 frequency ranges (bands) are 150 to 170 MHZ (VHF), 450 to 470 MHZ (UHF) & the 900 MHZ. The area of coverage varies due to terrain, antenna height, frequency band & vegetation. The spread spectrum uses one of three methods to spread the data signal: slow hoppers (frequency hopping), fast frequency hoppers and direct sequence.
Figure-4: Network Configurations
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2.2.3. Computer Systems used by SCADA (NPCC) As already discussed, two computer systems are used by National Power Control Centers. One is at NPCC Islamabad, which is used for NCC Islamabad and also for Regional Control Center North. One Computer System is doing its operations at Regional Control Center Jomshoro. Computers at NPCC/RCC are of 1980’s technology having primary memory of 4 Mega Bytes and secondary memory (H.D) of 340 Mega Bytes. Both the systems are linked via six channels through Wapda’s Analogue microwave system. Computer Systems are basically the hardware used at the control station (room). Basically, it comprises of the personal computer (PC) complete with the attached peripheral (connected) devices including the monitor, the printers, data loggers & mimic panel (having lamp & analog outputs) that allows the operator to monitor & control the field data & distributed devices/equipment over the plant or city. The PC serial port is connected to a suitable modem (system box) for communication with the field RTUs. The PC will have the appropriate operating system (the platform which the SCADA software is going to run under), the microprocessor, the hard disk, the floppy disk drive, the CDROM drive, the memory (RAM), the graphical adapter, support for multi-screen adapter boards and logical input/output for pen recorders, mimic panel, etc.
a) Keyboard essential functions: The key board can be divided into 4 sections: 1) Alphanumeric keypad that is used to enter text & numbers by the operator. 2) Editing keypad which includes the the cursor control keys and certain user-defined functions. 3) Auxiliary keypad which includes the user defined function keys that would reference the most important pictures in the system. 4) Top row function keys which includes the system special functions and more user defined functions.
b) Essential displayed information (on the monitor): The pictures (screens) are displayed in text and/or graphics mode, the display will have the following minimal instructions/information: 1) Data & time, title of screen & page number. 2) The next input steps the operator is allowed to make. 3) The last alarm in the system.
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4) The operators input part plus the part of the screen that displays the error message if the operator enters wrong values or illegal sequences. 5) The process/data of the selected zone of the modeled system.
c) The software: It includes the following operator's tools: database organization, the screen (picture) builder, programming facility and a shell-like application.
2.2.4. Remote Terminal Units (RTUs) NPCC Computer System and Regional Control Centre (North) is connected with total of 25 RTUs. Regional Control Centre (South) having separate Computer System is separately connected to 11 RTUs. It has a front end to front end link with NPCC subscription link. In-plant SCADA system, Tarbela is further connected with 11 RTUs, which has a Front end to Front end link with NPCC only for selected values ( due to less memory of NPCC SCADA system) from selected RTUs via single subscription link through PLC. RTUs are the devices that accept digital, analog and counter inputs and provide digital and analog output. The inputs to the RTU are the indications/status (digital ON/OFF, closed/tripped, etc), the values (analog-measurands & levels) and pulses of the field devices i.e. the information to be monitored and reported to the master computer. To affect control on the remote devices, the analog & discrete output of the RTU is connected to the pertinent devices/equipment. Discrete output is used to drive an external relay, to operate a circuit breaker (closing it or tripping it), dropping a section of the feeder by opening a pole mounted switch or a a pad-mounted switchgear switch, to disconnect a service, to switch off a motor and other similar applications. Analog output are used to remotely control devices that requires an increment adjustment or a variable set point for example opening/closing a valve, controlling a tap changer, etc. Some of the RTUs used in SCADA, are intelligent. They are programmed to make certain decisions instead of sending the information to the master computer and wait for the instruction to come back. Such devices could be considered as upgraded to the controller level. The RTU requires a power supply, has several interfaces & multiple ports with the protocol selectable on a per-port basis. Some of the RTUs also have a microprocessor, RAM, real time clock, watchdog timer, LED indicators, internal diagnostics routines, fiber optic interface and an internal (built-in) modem.
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Major elements of RTU used by SCADA in Pakistan are shown in Figure-5. Master Station Communication Interface
Test/MMI
Power Supply
Logic Termination Substation Devices Figure-5: RTU Major Elements
Complete status of installed RTUs used by SCADA in Pakistan is given in the Table-1.
500kV(13Stations) Tarbela
Guddu
GhaziBarotha (NotComissioned )
New Rewat
Dadu
Hubco
Lahore
Jamshoro
Rousch
Gatti
MuzzafarGarh(NotComissioned )
New Multan
ShaikhMohammedi(NotComissioned)
220kV( 21 Stations ) Mardan
Nishatabad
IslamabadPeshRoad(NotComissione
Burhan
Kala Shah Kaku
Daud Khail ( Not Comissioned )
Gakhar
Bund Road
AES Lal pir
Mangle
NGPS Multan
AES Pakgen
New Kot Lakhpat
Sibbi
KAPCO
Yousaf Wala
Hala Road
Uch Power
Jaranwala Road
Sialkot ( Not Comissioned )
Chashnup
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132kV(11 Stations ) Warsak
GTPS Faisalabad
Fuji Kabirwala
Kel
Saba Power
Liberty Power
Kotri
ChasmaHydroPower(NotComissioned)
Habibullah coastal
Sepcol
Japan ( Not Comissioned )
Table-1: Status of Installed RTUs
2.3. Miscellaneous information about SCADA (NPCC) 2.3.1. Data Acquisition facilities Different values and indications, which are either monitored or acquired by SCADA at NPCC, are listed below: Analogue Values
MW
MVAR
Voltages
Frequency
Tap position
Status (Indications)
Breaker Open / Close and error Status (X)
Isolator Open / Close and error Status (X)
Protection signals (only for IPPs)
Synchro-check Signals ( Freq, Phase and Voltage difference)
AGC signals
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2.3.2. Remote Control Facilities Different Remote control operations that are provided by SCADA at NPCC are:
Breaker Open / Close (Only for 500KV breakers)
Tap regulation (Only for 500/220 KV Transformers.)
Automatic Generation Control
These facilities at National Control Centre are limited due to poor communication and limited interfacing.
2.3.3. Display Types Various types of Display facilities at NPCC are: Single line diagrams Curves Events Alarms Reports, power system Post mortem review (only for analogue values on 30 Seconds Resolution)
2.3.4. Storage Capacities Values and indication storages are the facilities provided at SCADA (NPCC). They are given below: Values : Storage Time 10 Seconds Instant values only for AGC = 250 : (45 min) 30 Seconds Instant……………………… = 1000 : ( 1Hrs ) 15 Minutes Instant ………………………= 650 : (5 days) One Hour Instant………………………….. ALL : (5 days) One Hour Indications………………………ALL : (5 days)
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3. Suggestions for improvement in the status of Present SCADA System Present SCADA system used in Pakistan is of 1980’s technology and has various limitations and problems, which needs to be resolved. I am providing some suggestions for improving its status, operation, etc. These information and suggestion are based upon my own study regarding SCADA and also on various materials that I have collected from NPCC Islamabad. First of all, it is extremely important to discuss here that, for optimization the cost of generation; following factors are key areas of concern:
Minimization of transmission losses Quick restoration of supply Minimization of outages Avoiding major collapse Quality and reliability of supply Voltage and frequency control By upgrading existing SCADA & Tele-communication with latest version
All the above terms have importance at their own place, but the last one is much worthy here. Present SCADA using 1980’s technology, should be upgraded with the state of art technology for optimization purpose. Various technical features of SCADA, which can be upgraded, are given table wise below:
3.1. SCADA Hardware Existing System
Proposed New System
Make :
Latest Available At the time of Procurement
Modcomp USA /ABB
Operating System MAX-IV ( DOS environment)
Window Based (User Friendly)
Capacity
:
4 MB
Latest Available At the time of Procurement Present day PC RAM : 1000 MB
Hard Disk Space
:
340MB
Latest Available At the time of Procurement PC Hard Disk : 40000- 80000 MB
Speed
:
30 MHz
VDUs are of special design, Replacement of VDU is due ( Life was 10 years) Cost is very High, being of special
Normal PC Speed > 2000 MHz VDU are of common design. Easy replacement being readily available. Low Cost.
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design Interfacing with PC is not provided in the system.
Can be easily Interfaced with PC.
Spares no longer manufactured becoming difficult to maintain Technical support from manufacturer if required may not be available in future.
In new system this problem will be solved.
Table-2: SCADA Hardware
3.2. SCADA Software Existing System
Proposed New System
New application Software cannot be used due to less memory and speed.
New Software would be easy to run. The following new software are proposed which are essential for NPCC. Unit Commitment and economic dispatch. Automatic Generation control. Optimal Power flow. Load Forecasting Software. Training Simulator software. On line Load flow studies. Contingency Analysis Table-3: SCADA Software
3.3. Remote Terminal Units Existing System
Proposed New System
Only ABB Collector 300 and Collector 400 RTUs can be Interfaced
RTUs of any make & type can be interfaced.
Cost Per RTU : Rs 12.5 Mln. Existing Stations( without RTUs): 9 Future stations up to 2008 : 17 Cost of 26 RTUs ( 9 + 17) :Rs.325 Mln.
Rs. 3 Mln. Rs. 78 Mln.
Expensive Transducers are required due to software limitation and is proprietary item of ABB
Low cost transducers can be used.
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Expensive spares have to be purchased from manufacturer being proprietary item of ABB
Cheap Spares can be purchased from open market.
Limit to interface number of RTUs is 40, which is about to exhaust.
Communication Lines Interfacing Limit of both RTUs and Lines would be enhanced.
Global Positioning system ( GPS ) for time clock cannot be interfaced.
GPS is easy to interface.
Only 6 – channels for interfacing with other system.
Enhanced number of channels.
Table-4: Remote Terminal Units
3.4. Telecommunications Existing System
Proposed New System
Analogue Microwave backbone from Islamabad to Jamshoro
Digital Microwave communication highway from Islamabad to Jamshoro.
Number of Channels
Number of Channels
Channels saturated
Capacity
:
60
: 630
already
Channels capacity enhancement possible up to 1890 Channels.
Spares no longer manufactured, Becoming difficult to maintain.
Spare availability shall be ensured for about 15 years.
Failure rate of system is on increasing trend.
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System is working in 1 + 0 -configuration at several points instead of 1 + 1 requirement. Table-5: Telecommunications
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References [1] A.S. Siddiqui & Aziz Ahmad: ‘Use of SCADA Systems in Power System Automation’ International Journal of Engineering Studies, Research India Publications, ISSN 0975- 6469 Volume 2, Number 2 (2010), pp. 183–192. http://www.ripublication.com/ijes.htm [2] John Mc Donald ‘LADWP Taps Non Operational Data with Power System Data Mart Project’ P & E Magazine, March/April 2006. [3] W.J. Ackerman ‘The Impact of IEDs on the Design of Systems Used for Operation and Control of Power Systems.’ Power System Management and Control Conference, 17-19 April 2002. [4] Loney, George Coach ‘Oracle Complete Reference’ Tata McGraw-Hill Publications, ISBN 0-07-049902-0. [5] National Power Control Centre-Islamabad, Pakistan
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