Presentation On Substation 220 Kv 2m1j2f

P.P.T ON STUDY OF SUBSTATION AND AVAILABILITY TARIFF SUBMITTED BYPIYUSH BANSAL 101084007

INTRODUCTION ABOUT ABLOWAL SUBSTATION

It is situated in Sarabha Nagar 7.5 KM from Railway Station.Until 1978 it was transmitting 132KV energy and on 29 July 1982 it was upgraded to 220KV.It is has four parts. 1. 22KV switch yard 2. 220/66KV switch yard 3. 66/11KV switch yard 4. 11KV control room The 220 KV Ablowal grid has incoming supply of 220 KV from Gobindgarh and Fagun Majra and it supplies the stepped down power of 66 KV to the areas of Rakhra, Pasiana, Patiala, DCW,Shakti Viharand Sirhind Road and the stepped down power of 11 KV to the areas of Model Town Jail Road, Dashmesh Nagar, Lung, Maltex (independent feeder), Bakshiwala and Asa majra.

Schematic Power System Diagram

ADVANTAGES OF HIGH VOLTAGE The use of higher voltage (hence lower current in the line) reduces voltage drop in line resistance and reactance. 1. It reduces the losses and efficiency of line inceases. 2. As current decreses, size of conductor (cross sectional area) decreases. 3. Impedance Drop reduces which increses voltage regulation of the line. As high transmission voltage makes the system economical, but intial cost ofsystem increases because decrease in current increases the voltage level.Thus , capital cost increases due to 1. Increase in tower heights (more ground clearance) 2. Larger cross arms are needed. 3. Rating of protective equipments (like circuit breakers) increases. But besides capital cost increases, decrease in losses are able to generate more revenues to the supplier.

TYPES OF SUBSTATION According to the service requirement: • Transformer substation • Power factor correction substation • Converting substation • Industrial substation According to the constructional features: • Indoor substation • Outdoor substation • Underground substation • Polemounted substation

EQUIPMENTS USED IN SUBSTATION POWER TRANSFOMERS

Substation has the two220/66kv power transformers (100 MVA) installed made by BHEL and ABB and two 66/11 kv power transformer (20 MVA) made by ECE and TA. The power transformers are used to step down the220 KV incoming to 66 kv and further step down 11kv.

66/11 KV POWER TRANSFORMER

220/66 KV POWER TRANSFORMER

NAME PLATE OF T/F • • • • • • •

220/66KV (MADE BY ABB) 70 M.V.A(ONAN),85 M.V.A(ONAF),100M.V.A(OFAB) 174.94/1049.73 A (ONAN) YNyn0 (VECTOR GROUP) CLASS C INSULATION SHORT CIRCUIT CURRENT (1.75/5.83 KA) FOR 5 SEC. 65920 LITRES OF OIL

MAINTENANCE 1. Inspect bushings for cracked porcelain and deterioration.

2. Check the dielectric strength of transformer oil by oil tester in which oil is put in 2 mm gap and voltage is increased up to 2kv.If flash occur then oil is dehydrated.

Oil tester 3. Check the color of silica gel in breather ;it must be blue in color if it is turned pink then replace it

INSTRUMENT TRANSFORMER CURRRENT TRANSFORMERES Current transformer (CT) steps down the current of a circuit to a lower value current transformer. It 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.

RATING OF C.T • • • • • •

SYSTEM VOLTAGE 220 KV CURRENT RATING 150-300/1-1-1 A ACCURACY CLASS .2S FOR METERING 5P10 FOR PROTECTION BURDEN 200 V.A

POTENTIAL TRANSFORMER It steps down the voltage level of line for – 1. Measurement : voltmeter, frequency meter,kw meter, kwh meter ,power factor meter. 2. Control & protection used in directional over currentprotection and under frequency relay operation. 3. P.T IS ALSO CALLED (C.V.T)CAPACITOR VOLTAGE T/F. 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 relays.

RATING OF P.T • • • • • • •

VOLTAGE 220 KV INSULATION LEVEL 400/1050 KV VOLTAGE RATIO (VOLT) 220000/ ACCURACY CLASS 3P BURDEN 200 V.A H.S.V 245 KV OVER VOLTAGE FACTOR 1.2 TIMES (15-30 SEC)

CIRCUIT BREAKER • A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. TYPES • BULK OIL CIRCIUT BREAKER • MINIMUM OIL CIRCUIT BREAKER • AIR BLAST CIRCUIT BREAKER • VACCUM CIRCUIT BREAKER • SF-6 CIRCUIT BREAKER

SF6 CIRCUIT BREAKER • • • • • • • • • •

A circuit breaker in which the current carrying s operate in Sulphur Hexafluoride or SF6 gas is known as an SF6 Circuit Breaker. Now a days SF-6 circuit breaker replacing ABCB & MOCB due to the following properties: Excellent insulating, arc extinguishing, physical and chemical properties of SF6 gas is greater advantage of SF6 circuit breakers The gas is non-inflammable and chemically stable. The decomposition products are nonexplosive i.e, rhere is no risk of fire or explosion Electrical clearances are very much reduced because of high dielectric strength of SF6 Its performance is not affected due to variation in atmospheric conditions It gives noiseless operation it does not make sound like air-blast circuit breaker during operation No frequent replacement-arcing time is small owing to outstanding arc quenching properties of SF6 and therefore erosion is less. Hence s do not suffer oxidation Therefore is no reduction in dielectric strength of SF6 since no carbon particle is formed during the arcing Minimum maintenance. The breaker may require maintenance once in four to ten year Same gas is re-circulated into the circuit thereby reducing the requirement of SF6 gas.

RATING OF SF6 C.B • • • • • • •

RATED VOLTAGE 66KV NORMAL CURRENT 1700 A SYMM. BREAKING CAPACITY 2000 MVA BREAKING CURRENT 3980 A RATED MAKING CAPACITY 5100MVA SHORT TIME RATING 5000 A (3 SEC) GAS PRESSURE 16.5 Kg/cm²

ISOLATOR An isolator is a non load-breaking switch, and it provides a visible means of isolating a component, such as a circuit breaker, transformer, etc., from the high-voltage lines, whenever it is necessary to perform maintenance of that component. An isolator does not have any specified current breaking capacity or current making capacity. Opening and closing of a current carrying circuit is performed by a circuit-breaker. Normally, isolators come in pairs, with one on each side of the component to be isolated. Isolators are only opened after the load current has been broken using a circuit breaker, and must be closed before the circuit breaker is reclosed. In some designs the isolator switch has the additional ability to earth the isolated circuit thereby providing an additional safety

LIGHTING ARRESTER

A lightning arrester is a device used to protect the insulation and conductors of the system from the damaging effects of lightning. It is a device designed to protect electrical equipments from high voltage surges and to limit the duration and amplitude of the follow current.

LIGHTING ARRESTER (CONTD.) The typical lightning arrester has a high-voltage terminal and a ground terminal. When a lightning surge (or switching surge, which is very similar) travels along the power line to the arrester, the current from the surge is diverted through the arrestor, in most cases to earth. Generally arresters are connected in parallel with the equipment to be protected, typically between phase and earth for three phase installations There are 2 types of designs available for EHV Surge-Arrester. 1. Arrester (Value Type) 2. Metal Oxide Surge-Arrester RATING OF LIGHTING ARRESTER (220 KV) 198 KV 10 KA

CAPACITOR BANK A capacitor bank is used in the outgoing bus so that it can maintain the voltage level same in the outgoing feeder. Capacitor Control is usually done to achieve as many as possible of the following goals: Reduce losses due to reactive load current, reduce kVA demand, decrease customer energy consumption, improve voltage profile, and increase revenue. Indirectly capacitor control also results in longer equipment lifetimes because of reduced equipment stresses. Experience shows that switched feeder capacitors produce some of the fastest returns on equipment investment .Ablowal Substation has two capacitor banks of 2.722 MVAR each.

P.L.C.C (POWEL LINE CARRIER AIDED COMMUNICATION)

• • • • •

Reliable & fast communication is necessary for safe efficient and economical power supply. To reduce the power failure in extent and time, to maintain the interconnected grid system in optimum working condition; to coordinate the operation of various generating unit communication network is indispensable for state electricity boardThe PLCC can be used for the following facilities: Telephony Teleprotection Remote control or indication Telemetry Teleprinting

COMPONENTS OF P.L.C.C WAVE TRAP Consists of lighting arrrester, main coil and tunning device in parallel. MAIN COIL Offeres high impedance to carrier freq.(50khz to 500khz) and connected in series with line.Lighting Arrester protects main coil from high voltages. COUPLING CAPACITOR The modulated carrier is let into power line through coupling capacitor specially designed to with stand line voltage under all weather condition. The upper end of the coupling capacitor is connected directly to the line and the lower end is connected to the ground through a carrier frequency chock coil or drain coil. Thus coupling capacitor forms the link between the PLCC equipment and power line. The coupling capacitor used in PSEB is 2200pf capacitance.

SCHEMATIC ARRANGEMENT OF SWITCH GEAR

EVENT OF FAULT

• • • • •

Whenever any fault occurs in the feeder circuit, proportionate secondary current of the CT will flow through the current coil of the relay due to which mmf of that coil is increased. This increased mmf is sufficient to mechanically close the normally open of the relay. This relay actually closes and completes the DC trip coil circuit and hence the trip coil is energized. The mmf of the trip coil initiates the mechanical movement of the tripping mechanism of the circuit breaker and ultimately the circuit breaker is tripped to isolate the fault. Some Relays used in Sub-Station Over Current Relay Over Voltage Relay Differential Relay Restricted Earth Fault Relay Buchholz Relay

PROCEDURE OF REPAIR When any repair/maintenance is done then certain steps are followed DURING OPENING 1. C.B is opened manually 2. ISOLATOR is opened 3. ISOLATOR IS EARHED DURING RECLOSING 1.EARTH is disconnected 2.ISOLATOR is closed 3.C.B is closed

INTRODUCTION TO A.B.T The term Availability Tariff, particularly in the Indian context, stands for a rational tariff structure for power supply from generating stations, on a contracted basis. The power plants have fixed and variable costs. The fixed cost elements are interest on loan, return on equity, depreciation, O&M expenses, insurance, taxes and interest on working capital. The variable cost comprises of the fuel cost, i.e., coal and oil in case of thermal plants and nuclear fuel in case of nuclear plants. In the Availability Tariff mechanism, the fixed and variable cost components are treated separately. The payment of fixed cost to the generating company is linked to availability of the plant, that is, its capability to deliver MWs on a day-by-day basis. The total amount payable to the generating company over a year towards the fixed cost depends on the average availability (MW delivering capability) of the plant over the year. In case the average actually achieved over the year is higher than the specified norm for plant availability, the generating company gets a higher payment. In case the average availability achieved is lower, the payment is also lower. Hence the name ‘Availability Tariff’.

A.B.T IN INDIA To recapitulate, the Indian version of Availability Tariff comprises of three components: (a) capacity charge, towards reimbursement of the fixed cost of the plant, linked to the plant's declared capacity to supply MWs, (b) energy charge, to reimburse the fuel cost for scheduled generation (c) a payment for deviations from schedule, at a rate dependent on system conditions. The last component would be negative (indicating a payment by the generator for the deviation) in case the power plant is delivering less power than schedule.

NECESSITY OF A.B.T Prior to the introduction of Availability Tariff, the regional grids had been operating in a very undisciplined and haphazard manner. There were large deviations in frequency from the rated frequency of 50.0 cycles per second (Hz). Low frequency situations result when the total generation available in the grid is less than the total consumer load. These can be curtailed by enhancing generation and/or curtailing consumer load. High frequency is a result of insufficient backing down of generation when the total consumer load has fallen during off-peak hours. The earlier tariff mechanisms did not provide any incentive for either backing down generation during off-peak hours or for reducing consumer load / enhancing generation during peak-load hours. In fact, it was profitable to go on generating at a high level even when the consumer demand had come down. In other words, the earlier tariff mechanisms encouraged grid indiscipline.

CONCEPT OF U.I Unscheduled Interchange (UI) in Availability Tariff terminology at a rate dependent on frequency at that time. If the energy actually supplied is less than what is scheduled, the generating station shall have to pay back for the energy shortfall, at the same frequency linked rate.

When the frequency is 50.5 Hz or higher, the UI rate is zero, which means that the generating station would not get any payment for the extra energy supplied. It would burn fuel for producing this extra energy, but would not get reimbursed for it at all.

POWER TRADING STEPS TAKEN DURING OFF PEAK PERIOD GENERATING UTILITY 1.Back down the station during off-peak hours 2.Find a buyer for the above off-peak surplus 3.Instead of selling the off-peak surplus power through a bilateral agreement, generate power to its full capability even duringoff peak hours STATE BOARDS 1.Find a buyer for the off-peak surplus, and schedule a bilateral sale. 2.Draw power only according to its actual schedule.

U.I. RATE vs. SYSTEM MARGINAL COST UI rate is tightly linked to grid frequency. As the frequency is same all over an A.C. system, and can be readily seen through a simple frequency meter, it is easily possible to know the prevailing UI rate anywhere in the system, without the help of any communication system. With this on-line knowledge of the current UI rate, a State would know what it would have to pay for an extra MW that it may draw from the regional grid. It can readily compare this with the fuel cost it would save if generation were reduced by one MW at its own station, having the highest variable cost. If the UI rate is lower than the latter, it would be beneficial for the State to reduce its own generation and draw the replacement energy from the regional grid, till it has backed down all generation having a variable cost higher than the current UI rate. In the process, the State’s marginal generation cost would move down, towards the prevailing UI rate

EXPECTATIONS FROM CENTER STATIONS • The above availability forecast should be the best assessment by the plant operators of the av operational during the day, the availability forecast can be trimmed by 10 MW output capability. • In case a unit or auxiliary is required to be taken out of service during the next day, it would be expected that it is planned to be done after the morning(during off peak period) • If a unit or auxiliary is to be brought back in operation, it should be so planned that plant availability increases before the onset of morning / evening peak hours.

ROLE OF S.L.D.C • Even if a State overdraws in a low-frequency situation, it would mean meeting consumer demand which would not have been met otherwise, and is beneficial from this angle. However, it has following adverse implications: • The regional grid may be endangered if frequency falls below 49.0 Hz, or if some transmission element gets excessively overloaded. RLDC may then ask the SLDC to curtail its overdrawal and SLDC must take necessary action immediately. • The over-drawing State shall have to pay UI charges at a high rate. The SLDC would have to be sure that it is in the State’s overall interest. PREVENTIVE ACTION • Maximize generation at intra - State stations having variable costs lower than prevailing UI rate. (This can be in the form of standing instructions, i.e., frequency - linked dispatch guidelines). • Harness captive and co-generation, to the extent available at a price lower than the prevailing UI rate.

ADVANTAGES OF A.B.T • The mechanism has dramatically streamlined the operation of regional grids in India. Firstly, through the system and procedure in place, constituents’ schedules get determined as per their shares in Central stations, and they clearly know the implications of deviating from these schedules. • Any constituent which helps others by under-drawal from the regional grid in a deficit situation, gets compensated at a good price for the quantum of energy under-drawn. Secondly, the grid parameters, i.e., frequency and voltage, have improved, and equipment damage correspondingly reduced. • During peak load hours, the frequency can be improved only by reducing drawls, and necessary incentives are provided in the mechanism for the same. High frequency situation on the other hand, is being checked by encouraging reduction in generation during off-peak hours. Thirdly, because of clear separation between fixed and variable charges, generation according to merit-order is encouraged .

CAUSES OF GRID DISTURBANCE 1.Weak Inter-regional Corridors due to multiple outages.The system was weakened by multiple outages of transmission lines in the WR-NR interface. 2.Effectively, 400 kV Bina-Gwalior-Agra (one circuit) was the only main AC circuit availablebetween WR-NR interface prior to the grid disturbance. 3.High Loading on 400 kV Bina-Gwalior-Agra link: The overdrawal by some of the NRutilities, utilizing 4.Unscheduled Interchange (UI), contributed to high loading on this tie line. 5.Inadequate response by SLDCs to the instructions of RLDCs to reduce overdrawal by the NR utilities and underdrawal/excess generation by the WR utilities. 6.Loss of 400 kV Bina-Gwalior link: Since the interregional interface was very weak tripping of 400 kV Bina Gwalior line on zone-3 protection of distance relay caused the NR system to separate from the WR. This happened due to load encroachment (high loading of line resulting in high line current and low bus voltage). However, there was no fault observed in the system.

MEASURES NEEDED • Load Desptach Centres should be equipped with Dynamic Security Assessment and faster State Estimation tools. • NR constituents were instructed by NRLDC to carry out load shedding to relieve the Gwalior-Agra line loading. However, the quantum of load shedding undertaken by the NR constituents seems to be insignificant. WRLDC also issued similar instructions to its constituents for reduction in generation. • To avoid congestion in intra-State transmission system, planning and investment at State level need to be improved • Proper telemetry and communication should be ensured to Load Despatch • Centres from various transmission elements and generating stations

CONCLUSION • I think that my training was successful and 220 kv substation at Ablowal is an excellent training centre for inquisitive emerging electrical engineers to learn about the high voltage electricity transmission and distribution with the the functioning of all other protective devices. In the training session we came to know about the fundamentals of power system which may be quite useful in future • I also learn about AVAILABILITY TARIFF for disciplined and accurate operation of power system.The unique feature of this tariff, to tackle the peculiar problems of grid operation in india, is the frequency linked pricing of the Unschedule Interchange.

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