Report for Six Week Training At GURU HARGOBIND THERMAL PLANT (GHTP) LEHRA MOHABBATIn Electrical Maintenance 1 cell Submitted to- Submitted byDivanshu Garg Ms--------------------EIED Thapar University, Patiala 100904027 B Tech. Electrical (2009-2013) Thapar University, Patiala 3 Acknowledgement I am extremely thankful & indebted to the numerous PSPCL Engineers, who provided vital information about the functioning of their department thus helping me to gain an overall idea about the working of organization. I am highly thankful for the support & guidance of each of them. I am highly indebted to my project guide, Er. Baldev Singh (J.E.), Er. Rajinder Bhagat (Sr. XEN) for giving me his valuable time and helping me to grasp the various concepts of switchyard equipments. Last but not the least, I would like to thank my parents & all my fellow trainees who have been a constant source of encouragement & inspiration during my studies & have always provided me support in every walk of life. - Divanshu Garg 4 Certificate 5 About PSPCL Punjab State Power Corporation Limited (PSPCL) is the electricity generating company of the Government of Punjab state in India. PSPCL was incorporated as company on 16-04-2010 and was given the responsibility of operating and maintenance of State's own generating projects. The business of Generation of power of erstwhile PSEB was transferred to PSPCL. The existing Thermal Power Plants under PSPCL are GURU NANAK DEV THERMAL PLANT BHATINDA, GURU GOBIND SINGH SUPER THERMAL PLANT ROPAR and GURU HARGOBIND THERMAL POWER PLANT LEHRA MOHABBAT (BHATINDA). The existing Hydro Power Plants are RANJIT SAGAR DAM (HYDRO ELECTRIC PROJECT), SHANAN POWER HOUSE (HYDRO ELECTRIC PROJECT), ANANDPUR SAHIB HYDEL PROJECT (HEP), MUKERIAN HYDEL PROJECT STAGE - I and U.B.D.C. HYDRO ELECTRIC POWER HOUSE STAGE I & II. MEGAWATT STORY Total power from state's current sources Peak demand in 2011-12 Demand increase per year Present shortfall Thermal generation (Ropar, Lehra Mohabbat, Bathinda) Hydel generation BBMB projects Central pool and banking Solar (9 plants) Biomass (3 plants) Micro Hydel (2 plants) 6,950 MW 10,010 MW 8% 3,100 MW 2,620 MW 1,000 MW 1,250 MW 3,200 MW 14.5 MW 6 MW 0.85 MW 6 1. Brief History of Plant Ever widening gap between the power demand and its availability in the state of Punjab was one of the basic reasons for envisaging a thermal plant at lehra mohabbat Distt. Bathinda. The others favourable factors were low initial cost and generation period as compared to hydroelectric generating stations, its good railway service and proximity to load centre. Initially it was going to set up at Bathinda under GNDTP but the air force personal restricted its set up at Bathinda hence plant shifted to Lehra Mohabbat about 22 Km from Bhatinda city. Later this plant was approved as a separate autonomous body with its name as Guru Hargobind Thermal Plant .The Construction of plant commenced in 1992. It consists of 2 stages:Stage 1:First unit commissioned on 27/12/1997 Second unit commissioned on 16/10/1998 Stage 2:Third unit commissioned on 16/10/2008 Fourth unit commissioned on 31/01/2009 The capacity of both units of stage 1 is 210 MW each and that of stage 2 is 250 MW each. It meets 20-25% of total power requirement of Punjab. The main companies whose technology paved the way for the plant are Tata Honeywell and BHEL in turbine and boiler control. 7 1. General procedure 2.1 Introduction Power is generated from two units of stage 1 (each 210 MW) at 15.75 KV and two units of stage 2 (each 250 MW) at 16.5 KV which is stepped up through 250 MVA (15.75/220 KV) and 315 MVA generators transformer respectively. Power is transmitted through eight 220 KV bi-directional feeders. The whole system is connected to northern grid. Supply to auxiliary of thermal plant is given through UAT (Unit Auxiliary T/F) of output 6.6 KV and UST (Unit Station T/F) of output 6.6 KV. 2.2 Site Selection and location Bathinda district is located in southern part of Punjab. GHTP is near Rampura-Phul on Bathinda Barnala road. 2.3 Railway Rail line is taken from lehra mohabbat railway station from Dhuri Bathinda Broad Gauge railway line. 2.4 Water resource Water requirement of all type of need is met from Bathinda branch of Sirhind canal. 2.5 Geology The subsoil of the area generally consists of alternating layers of poorly graded silt sand and clay sand. 2.6 Climate Bhatinda has hot dry but very healthy climate. Relative HumidityMax: 83% Min: 22% Rainfall depends on SW monsoon. Average annual rainfall is around 600 mm 8 2.7 Fuel Used Primary fuel is Coal from PANEM (PSEB captive mine established as joint venture with EMTA group), CCL & ECL, and the subsidiary Companies of coal India Limited. Secondary fuel is Furnace Oil and Light Oil. 2.8 Total energy contribution Total energy contribution is 220.8 Lac units daily. 2.9 Cost of generation Cost of generation is 184.65 paisa per unit. 9 3. Electrical maintenance circle Electrical maintenance circle is one of the most important Departments of GHTP. It is divided into four different cells to carry out the maintenance of electrical equipments in thermal plant so the thermal plant will work with maximum efficiency without any shutdown. Organisation chart of EMC Electrical maintenance circle EM 1 cell 220 KV Switchyard 66 KV Switchyard All Transformers, Lighting Protection cell Protection system, Fix detection and alarm, Communication system, Variable frequency drives, Gen. Excitation system EM 3 HT & LT motors, Generators, bus ducts lifts, hoists EM 4 HT & LT switchgear, DC batteries, Battery chargers 10 The four cells are: Electrical maintenance 1 cell:Maintenance of all lighting equipments, maintenance of 220 KV grid and 66 KV grid. Protection cell:Maintenance of equipments for protection of all HT and LT auxiliaries, fire fighting and telephone exchange. Electrical maintenance 3 cell:Maintenance of HT and LT motors, DG sets, Turbo generators, Bus ducts, hoists, EOT cranes. Electrical maintenance 4 cell:Maintenance of all switchgear equipments of plant. 11 3.1 Electrical Maintenance 1 cell It is divided into two parts: 3.1.1 220 KV switchyard, 66 KV switchyard, transformer yard 3.1.2 Lighting cell 3.1.1 220 KV switchyard, 66 KV switchyard, transformer yard Introduction Electrical energy management system ensures supply of energy to every consumer at all times at rated voltage, frequency and specified waveform, at lowest cost and minimum environmental degradation. The switchgear, protection and network automation are integral parts of the modern energy management system and national economy Modern 3 phase 50 Hz AC interconnected system has several conventional and non-conventional power plants ,EHV AC and HVDC transmission system ,back to back HVDC coupling stations, HV transmission network, substations, MV and LV distribution systems and connected electrical loads. To fulfil these requirements, state of art, scientifically and technologically advanced substation is required. The substation at GHTP has one 220 KV switchyard. There are four input units, two having a capacity 210 MW and two others have capacity of 250 MW. The generated voltage is limited to 15.75 kV and 16.5 KV which is stepped up to 220 KV via generating transformer manufactured by BHEL. A part of 15.75/16.5 KV supply is fed to unit auxiliary transformer, which is used to run the auxiliaries of the plant. After step up, the 220 KV output from the generator transformer is fed to either of the two bus bars through relays and circuit breakers and these are connected to various feeders through various equipments What is an Electrical Substation? "Electric Power is generated in Power Stations and transmitted to various cities and towns. An electrical substation is a subsidiary station of an electricity generation, transmission and distribution system where voltage is transformed from high to low or the reverse using transformers. Electric power may flow through several substations between generating plant and consumer, and may be changed in voltage in several steps. The word substation comes from the days before the distribution system became a grid. The first substations were connected to only one power station where the generator was housed, and were subsidiaries of that power station. 12 Elements of a substation Substations generally have switching, protection and control equipment and one or more transformers. In a large substation, circuit breakers are used to interrupt any short-circuits or overload currents that may occur on the network. Smaller distributions stations may use reclose circuit breakers or fuses for protection of distribution circuits. Substations do not usually have generators, although a power plant may have a substation nearby. Other devices such as power factor correction capacitors and voltage regulators may also be located at a substation. Substations may be on the surface in fenced enclosures, underground, or located in special- purpose buildings. High-rise buildings may have several indoor substations. Indoor substations are usually found in urban areas to reduce the noise from the transformers, for reasons of appearance, or to protect switchgear from extreme climate or pollution conditions. Where a substation has a metallic fence, it must be properly grounded (earthed) to protect people from high voltages that may occur during a fault in the network. Earth faults at a substation can cause a ground potential rise. Currents flowing in the Earth's surface during a fault can cause metal objects to have a significantly different voltage than the ground under a person's feet; this touch potential presents a hazard of electrocution. Transmission substation: A transmission substation connects two or more transmission lines. The simplest case is where all transmission lines have the same voltage. In such cases, the substation contains high-voltage switches that allow lines to be connected or isolated for fault clearance or maintenance. A transmission station may have transformers to convert between two transmission voltages, voltage control devices such as capacitors, reactors or static VAr compensator and equipment such as phase shifting transformers to control power flow between two adjacent power systems. Transmission substations can range from simple to complex. A small "switching station" may be little more than a bus plus some circuit breakers. The largest transmission substations can cover a large area (several acres/hectares) with multiple voltage levels, many circuit breakers and a large amount of protection and control equipment (voltage and current transformers, relays and SCADA systems). Distribution substation: A distribution substation transfers power from the transmission system to the distribution system of an area. It is uneconomical to directly connect electricity consumers to the high-voltage main transmission network, unless they use large amounts of power, so the distribution station reduces voltage to a value suitable for local distribution. The input for a distribution substation is typically at least two transmission or sub transmission lines. Input voltage may be, for example, 115 kV, or whatever is common in the area. The output is a number of feeders. Distribution voltages are typically medium voltage, between 2.4 and 33 kV depending on the size of the area served and the practices of the local utility. 13 Outgoing lines of substation: 220 KV line 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Barnala 1 Barnala 2 Himmatpura 1 Himmatpura 2 Bajakhana 1 Bajakhana 2 Bhatinda 1 Bhatinda 2 Mansa 1 Mansa 2 66 KV line 1. 2. 3. 4. 5. Vikram Cement factory Phool Bhuco mandi Rampura Lehra Mohhabat 14 Brief description of all outdoor Equipments: Bus Bars Bus bar is a term used for main bar of conductor carrying an electric current to which many connections can be made. These are mainly convenient means of connecting switches and other equipments into various arrangements. At GHTP there are two 220 KV bus bars and two 66 KV bus bars which are made of aluminium. All incoming and outgoing supplies are connected through the bus bars. Specifications: Minimum short circuit current in bus bars 40 KV Minimum phase to phase clearance 2.5 M Number of horizontal levels of tubular bus bar/flexible bus bars 2.0 M Height of tubular bus-bar of first level above ground 6 m Height of tubular bus-bar of second level above ground 4 m Tubular aluminium bus bar AL ASTMB241 4"IPS (International pipe standard) Lighting Arrestors These are equipments designed to protect insulators of power lines and electrical installations from lightning surges by diverting the surge to earth. High Voltage Power System experiences over voltages that arise due to natural lightning or the inevitable switching operations. Under these overvoltage conditions, the insulation of the power system equipments is subjected to electrical stress which may lead to catastrophic failure. Broadly, three types of overvoltage occur in power systems: (i) temporary over-voltages, (ii) switching over voltages and (iii) lightning overvoltage. The duration of these over voltages vary in the ranges of microseconds to sec depending upon the type and nature of overvoltage. Hence, the power system calls for overvoltage protective devices to ensure the reliability. Conventionally, the overvoltage protection is obtained by the use of lightning / surge arresters. Under normal operating voltages, the impedance of lightning arrester, placed in parallel to the equipment to be protected, is very high and allow the equipment to perform its respective function. Whenever the overvoltage appears across the terminals, the impedance of the arrester collapses in such a way that the power system equipment would not experience the overvoltage. As soon as the overvoltage disappears, the arrester recovers its impedance back. Thus the arrester protects the equipment from overvoltage. The technology of lightning arresters has undergone major transitions during this century. In the early part of the century, spark gaps were used to suppress this overvoltage. The silicon carbide gapped arresters replaced the spark gaps in 1930 and reigned supreme till 1970. During the mid 1970s, zinc oxide (ZnO) gapless arresters, possessing superior protection characteristics, replaced 15 the silicon carbide gapped arresters. Usage of ZnO arresters have increased the reliability of power systems many fold. Current Transformer In electrical engineering, a current transformer (CT) is used for measurement of electric currents. Current transformers, together with voltage transformers (VT) (potential transformers (PT)), are known as instrument transformers. When current in a circuit is too high to directly apply to measuring instruments, a current transformer produces a reduced current accurately proportional to the current in the circuit, which can be conveniently connected to measuring and recording instruments. A current transformer also isolates the measuring instruments from what may be very high voltage in the monitored circuit. Current transformers are commonly used in metering and protective relays in the electrical power industry. Current transformers are used extensively for measuring current and monitoring the operation of the power grid. Along with voltage leads, revenue-grade CTs drive the electrical utility's watt-hour meter on virtually every building with three-phase service and single-phase services greater than 200 amp. The CT is typically described by its current ratio from primary to secondary. Often, multiple CTs are installed as a "stack" for various uses. For example, protection devices and revenue metering may use separate CTs to provide isolation between metering and protection circuits, and allows current transformers with different characteristics (accuracy, overload performance) to be used for the devices. Care must be taken that the secondary of a current transformer is not disconnected from its load while current is flowing in the primary, as the transformer secondary will attempt to continue driving current across the effectively infinite impedance. This will produce a high voltage across the open secondary (into the range of several kilovolts in some cases), which may cause arcing. The high voltage produced will compromise operator and equipment safety and permanently affect the accuracy of the transformer. Potential Transformer These are used to step do the voltage to a level that the potential coils of indicating and monitoring instruments can read. These are also used to feed the potential coils of relays. The primary winding is connected to the voltage being measured and the secondary winding to a voltmeter. The PT steps down the voltage to the level of the voltmeter. 16 Power Transformer These are used to step up down the voltage from one ac voltage to another ac voltage level at the same frequency. In GHTP there are 2 power transformer located in substation which converts 220 KV to 66 KV of power 100 MVA each. Losses in the transformer are of the order of 1% of its full load kW rating. These losses get converted in the heat thereby the temperature of the windings, core, oil and the tank rises. The heat is dissipated from the transformer tank and the radiator in to the atmosphere. Transformer cooling helps in maintaining the temperature rise of various parts within permissible limits. In case of Transformer, Cooling is provided by the circulation of the oil. Transformer Oil acts as both insulating material and also cooling medium in the transformer. For small rating transformers heat is removed from the transformer by natural thermal convection. For large rating transformers this type of cooling is not sufficient, for such applications forced cooling is used. As size and rating of the transformer increases, the losses increase at a faster rate. So oil is circulated in the transformer by means of oil pumps. Within the tank the oil is made to flow through the space between the coils of the windings. Several different combination of natural, forced, air, oil transformer cooling methods are available. The choice of picking the right type of transformer cooling method for particular application depends on the factors such as rating, size, and location. 17 Wave Trap Line trap also is known as Wave trap. What it does is trapping the high frequency communication signals sent on the line from the remote substation and diverting them to the telecom/teleportation panel in the substation control room. This is relevant in Power Line Carrier Communication (PLCC) systems for communication among various substations without dependence on the telecom company network. The signals are primarily teleportation signals and in addition, voice and data communication signals. The Line trap offers high impedance to the high frequency communication signals thus obstructs the flow of these signals in to the substation bus bars. If there were not to be there, then signal loss is more and communication will be ineffective/probably impossible. Indicating and Metering Instruments Ammeters, voltmeters, wattmeters, KWhr meters and KVar meters are installed in substation to work over the currents flowing in the circuits and the voltages and power loads. Circuit breaker Circuit breakers are mechanical devices designed to close and open contact or electrical circuit under normal or abnormal conditions. CB is equipped with a strip coil directly attached to relay or other means to operate in abnormal conditions such as over power etc In GHTP 3 types of circuit breakers are used. SF6 C.B.is used to control 220 KV in switchyard. Vacuum C.B. is used to control 6.6 KV in switchgear and Air blast C.B. are used to control 415 V in switchgear. A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Its basic function is to detect a fault condition and, by interrupting continuity, to immediately discontinue electrical flow. Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city. Once a fault is detected, contacts within the circuit breaker must open to interrupt the circuit; some mechanically-stored energy (using something such as springs or compressed air) contained within the breaker is used to separate the contacts, although some of the energy required may be obtained from the fault current itself. 18 Small circuit breakers may be manually operated; larger units have solenoids to trip the mechanism, and electric motors to restore energy to the springs. The circuit breaker contacts must carry the load current without excessive heating, and must also withstand the heat of the arc produced when interrupting the circuit. Contacts are made of copper or copper alloys, silver alloys, and other materials. When a current is interrupted, an arc is generated. This arc must be contained, cooled, and extinguished in a controlled way, so that the gap between the contacts can again withstand the voltage in the circuit. Different circuit breakers use vacuum, air, insulating gas or oil as the medium in which the arc forms. Different techniques are used to extinguish the arc including: y y y y Lengthening of the arc Intensive cooling (in jet chambers) Division into partial arcs Zero point quenching (Contacts open at the zero current time crossing of the AC waveform, effectively breaking no load current at the time of opening. The zero crossing occurs at twice the line frequency i.e. 100 times per second for 50Hz ac and 120 times per second for 60Hz ac ) Connecting capacitors in parallel with contacts in DC circuits y Finally, once the fault condition has been cleared, the contacts must again be closed to restore power to the interrupted circuit. Capacitor Voltage transformer (CVT) In high and extra high voltage transmission systems, capacitor voltage transformers (CVTs) are used to provide potential outputs to metering instruments and protective relays. In addition, when equipped with carrier accessories, CVTs can be used for power line carrier (PLC) coupling. A capacitor voltage transformer (CVT) is a transformer used in power systems to step-down extra high voltage signals and provide low voltage signals either for measurement or to operate a protective relay. In its most basic form the device consists of three parts: two capacitors across which the voltage signal is split, an inductive element used to tune the device to the supply frequency and a transformer used to isolate and further step-down the voltage for the instrumentation or protective relay. The device has at least four terminals, a highvoltage terminal for connection to the high voltage signal, a ground terminal and at least one set of secondary terminals for connection to the instrumentation or protective relay. CVTs are typically single-phase devices used for measuring voltages in excess of one hundred kilovolts where the use of voltage transformers would be uneconomical. In practice the first capacitor, C1, is often replaced by a stack of capacitors connected in series. This results in a large voltage drop across the stack of capacitors that replaced the first capacitor and a comparatively small voltage drop across the second capacitor C2 and hence the secondary terminals. 19 Isolator In electrical engineering, a disconnecter or isolator switch is used to make sure that an electrical circuit can be completely de-energized for service or maintenance. Such switches are often found in electrical distribution and industrial applications where machinery must have its source of driving power removed for adjustment or repair. High-voltage isolation switches are used in electrical substations to allow isolation of apparatus such as circuit breakers and transformers, and transmission lines, for maintenance. In the substation following type isolators are used for the protection: Horizontal break centre rotating double break isolator: This type of construction has three insulator stacks per pole. The two one each side is fixed and one at the centre is rotating type. The central insulator stack can swing about its vertical axis through 900 . The fixed contacts are provided on the top of each of the insulator stacks on the side. The contact bar is fixed horizontally on the central insulator stack. In closed position, the contact shaft connects the two fixed contacts. While opening, the central stack rotates through 900 and the contact shaft swings horizontally giving a double break. The isolators are mounted on a galvanized rolled steel frame. The three poles are interlocked by means of steel shaft. A common operating mechanism is provided for all the three poles. One pole of a triple pole isolator is closed position. Pantograph isolator: Illustrates the construction of a typical pantograph isolator. While closing, the linkages of pantograph are brought nearer by rotating the insulator column. In closed position the upper two arms of the pantograph close on the overhead station bus bar giving a grip. The current is carried by the upper bus bar to the lower bus bar through the conducting arms of the pantograph. While opening, the rotating insulator column is rotated about its axis. Thereby the pantograph blades collapse in vertical plane and vertical isolation is obtained between the line terminal and pantograph upper terminal. 20 Pantograph isolators cover less floor area. Each pole can be located at a suitable point and the three poles need not be in one line, can be located in a line at desired angle with the bus axis. Isolator with earth switches (ES): The instrument current transformer (CT) steps down the current of a circuit to a lower value and is used in the same types of equipment as a potential transformer. This is done by constructing the secondary coil consisting of many turns of wire, around the primary coil, which contains only a few turns of wire. In this manner, measurements of high values of current can be obtained. A current transformer should always be short-circuited when not connected to an external load. Because the magnetic circuit of a current transformer is designed for low magnetizing current when under load, this large increase in magnetizing current will build up a large flux in the magnetic circuit and cause the transformer to act as a step-up transformer, inducing an excessively high voltage in the secondary when under no load. The main use of using the earth switch (E/S) is to ground the extra voltage which may be dangerous for any of the instrument in the substation. Capacitor bank: A capacitor bank is a grouping of several identical capacitors interconnected in parallel or in series with one another. These groups of capacitors are typically used to correct or counteract undesirable characteristics, such as power factor lag or phase shifts inherent in alternating current (AC) electrical power supplies. Capacitor banks may also be used in direct current (DC) power supplies to increase stored energy and improve the ripple current capacity of the power supply. 21 Transformer yard Generator Transformers The generator transformer is the first essential component for energy transmission, allowing energy supplied by the generator to be transferred to the network at the required voltage. To transmit power to various stations, we have to step down current because there are I2 R losses in transmission line. To do this, generator transformer is used. Power from each generator is stepped up to 220 KV by 250/315 MVA 50 Hz 3-phase 15.75/220 or 16.5/220 KV generator transformer with off load tap charger. There is one Generator transformer for each unit. Station Transformer 22 In general station transformer is used for supplying power to auxiliary equipment in the power plant when the plant is not generating any power. Station Transformer takes power from grid at 220 KV and steps it down to 6.6 KV. Rated KVA corresponds to the load of common auxiliaries of the station. This corresponds to the 10% to 15% of the rating of the generating power. These transformers are Outdoor type. Unit Auxiliary Transformer The Purpose of Unit auxiliary Transformer is to feed power to generator auxiliaries of that unit. These transformers are connected to generators and are used as stepping down transformers. The HV side transformer voltage corresponds to the voltage of the generating unit and the LV side voltage is stepped down to 6.6KV. Rated KVA of Unit Auxiliary Transformers is approximately 15% of the generating rating. Usually these transformers are outdoor transformers. One Unit auxiliary transformer is present for every generating unit. 23 Function of EM 1 cell Maintenance work includes periodical maintenance, breakdown maintenance, shutdown maintenance and attending all types of faults round the clock which occurs during running of equipment or otherwise for preventive maintenance including repair/replacement of any individual component or sub assembly or complete assembly for the equipment at 220 KV and 66 KV switch yard and transformer yard including bus bars, insulators, CTs and PTs, insulators, 66 KV capacitor bank, Super structures, marshalling boxes and other associated equipment, generator transformer, power transformer, power and control cables, service transformer, HV rectifier transformer, cables trays and trenches, electrical wiring of local panels of above equipment, including operation and maintenance. However physical/visual inspection and recording of readings on day to day basis will have to be done. 6.3.2 Lightning cell Periodical/Preventive maintenance, breakdown maintenance, shutdown maintenance and repair of plant lighting system and street lighting system and security lighting system in plant area(except coal handling plant ) of GHTP Lehra Mohabbat. Including 220 KV switchyard, 220 KV Transformer yard, 66 KV switchyard, 220 KV control room building, TG 0m to 15.5m floor, P.R.D.S. 21 floor, boiler 0m to 52m floors, service building, DG set house, DM plant, switchgears, RAWPH, ESP control room, electrical and mechanical workshop, cooling towers 110 m, chimneys 220 m, CW pump house and gas plant, canteen, dispensary, car/scooter stand, fire station, O and M store offices, store sheds, ware house, oil tank area and FODPH. 1. Lighting fixtures. 2. Decorative industrial type tube lighting fixtures. 24 3. L.T. cables installed at plants, security towers, chimneys and for street lighting. 4. L.D.Bs installed for AC and DC supply circuits. 5. Internal electrical installation of various non-residential buildings at the plant. References 1. Website: www.pspcl.in 2. Newspaper: Hindustan Times 3. Website: www.en.wikipedia.org 4. Book: A Course in Power Systems by J.B. GUPTA 25