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Under Guidance,
Mr.S R Tiwari
Mr.Sujeet Kr. Singh
“There are people, who, simply by being what they are, influence, encourage &
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  1. 1. 1 [Type text] Page 0 CXDDDD SUMMER TRAINING FROM UPPTCL Under Guidance, Mr.S R Tiwari (S.D.O.) Mr.Sujeet Kr. Singh J.E,UPPCL Summer Training report,132 KV Substation,MINTOPARK, ALLAHABAD Uttar PradeshPower CorporationLtd Submitted By Shashikant Bharti ,3rd year BBS college of engineering and Technology, Allahabad , UPTU
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  4. 4. 3 INTRODUCTION Uttar Pradesh Power Corporation Limited or in short UPPCL was recognised on January 14, 2000. UPPCL was formed because of the need of reforms in power and energy sector in Uttar Pradesh. These modifications were necessarily responsible for the management and planning of electrical power industry while considering electricity (power) generation, transmission, distribution and supply. At many places in the power system, it may be desirable and necessary to change some characteristics e.g. voltage, ac to dc, frequency, power factor etc. of electric supply. This accomplished by suitable apparatus called substation. For example; generation voltage (11 KV or 33 KV) at the power station is set up to high voltage (say 220 KV or 132 KV) for transmission of electric power. The assembly of apparatus (e.g. transformer etc.) used for this purpose in the substation. Similarly near the consumer’s localities the voltage may have to be step down to utilization level. This job is again accomplished by suitable apparatus called substation. The assembly of apparatus to change some characteristic of electric power supply is called substation. Figure 1 View of sub-station
  5. 5. 4 About 132/33kv minto park sub-station Figure 2 High voltage and low voltage transmission side The sub-station gets its 132KV supply from the power grids located at 220kv S/S REWA ROAD. At first a Lightning Assertor is used in a 3-phase transmission setup in order to protect the grid from surges due to lightning. After this comes the need to measure the voltage and current in the transmission lines. For that we use a Capacitor Voltage Transformer and Current Transformer respectively. Just like an ammeter and a voltmeter, a CT is connected in series with the transmission line whereas a CVT is connected parallel to the transmission line. Since they both are transformer they must have a transformation ratio. Now comes the time of implementing some safety features in the transmission line setup. For that we first use a Line Isolator and then a Bus Isolator. But these alone are not enough, so we use a Gas Circuit Breaker. These circuit breakers can be operated via control panel in the operating room. Four transformers of 40MVA capacity each are installed in Minto Park sub-station, thereby making a total station capacity of 160MVA. A lightning arrestor, current transformer and some control equipment are used on both sides of the transformers for better monitoring. The transformers step down the 132KV supply to 33KV supply. Then this 33KV supply is fed to the sixteen feeders that are installed in the sub-station. There is also a jack bus which is connected to the main bus with the help of a bus coupler. It is used as a backup feeder when some other feeder is under maintenance. Also
  6. 6. 5 there is another step down transformer installed in the sub-station which is used to supply electricity to the sub-station. ROUGH DESCRIPTION OFMINTO PARKSUB-STATION INCOMING LINE VOLTAGE:  132kv incoming-1 from 220kv S/S Rewa Road  132kv incoming-1 from 220kv S/S Rewa Road OUTGOING FEEDER VOLTAGE:  TAGORE TOWN  RAMBAGH  DARAGANJ-1  BAIRAHNA  DARAGANJ-2  STATION T/F-1  KYEDGANJ  GAUGHAT  ALLAHPUR  FORT ROAD  GEORGE TOWN TRANSFORMER CAPACITY: FOUR TRANSFORMER OF 40MVA ARE USED IN 132KV MINTO PARK SUB-STATION As we know, MVA=√3VI For 40 MVA, 40×106 = √3×132×103×I I = 175A (HV) 40×106 = √3×33×103×I I = 700A (LV) Therefore, total transformer capacity = 4×40MVA= 160MVA
  7. 7. 6 SINGLE LINE DIAGRAM :- Figure 3 Single line diagram 132 kv minto park
  8. 8. 7 SUBSTATIONS A substation is a part of an electrical generation, transmission and distribution system. Substations transform voltage from high to low, or the reverse, or perform any of several other important functions. Between the generating station and consumer, electric power may flow through several substations at different voltage levels. Substations may be owned and operated by an electrical utility, or may be owned by a large industrial or commercial customer. Generally substations are unattended, relying on SCADA for remote supervision and control. A substation may include transformers to change voltage levels between high transmission voltages and lower distribution voltages, or at the interconnection of two different transmission voltages.  Substations are classified by two broad categories:-  According to the service requirement:-  Transformer substation  Switch substation  Power factor correction substation  Frequency change substation  Converting substation  Industrial substation  Collector Substation  Convertor Substation
  9. 9. 8  Switching Substation  According to the constructional features:  Indoor substation  Outdoor substation  Underground substation  Pole mounted substation  TRANSFORMER SUBSTATION:-  They are known as transformer substations as because transformer is the main component employed to change the voltage level, depending upon the purposed served transformer substations may be classified into: a) STEP UP SUBSTATION  The generation voltage is steeped up to high voltage to affect economy in transmission of electric power. These are generally located in the power houses and are of outdoor type. b) PRIMARY GRID SUBSTATION  Here, electric power is received by primary substation which reduces the voltage level to 33KV for secondary transmission. The primary grid substation is generally of outdoor type. c) SECONDARY SUBSTATIONS  At a secondary substation, the voltage is further steeped
  10. 10. 9 down to 11KV. The 11KV lines runs along the important road of the city. The secondary substations are also of outdoor type. d) DISTRIBUTION SUBSTATION  These substations are located near the consumer’s localities and step down to 400V, 3-phase, 4-wire for supplying to the consumers. The voltage between any two phases is 400V & between any phase and neutral it is 230V.  SUBSTATIONCHARACTERISTICS:- 1. Each circuit is protected by its own circuit breaker and hence plant outage does not necessarily result in loss of supply. 2. A fault on the feeder or transformer circuit breaker causes loss of the transformer and feeder circuit, one of which may be restored after isolating the faulty circuit breaker. 3. A fault on the bus section circuit breaker causes complete shutdown of the substation. All circuits may be restored after isolating the faulty circuit breaker. 4. Maintenance of a feeder or transformer circuit breaker involves loss of the circuit. 5. Introduction of bypass isolators between bus bar and circuit isolator allows circuit breaker maintenance facilities without loss of that circuit.
  11. 11. 10 STEPS IN DESIGNING SUBSTATION :- The First Step in designing a Substation is to design an Earthing and Bonding System.  Earthing and Bonding:- The function of an earthing and bonding system is to provide an earthing system connection to which transformer neutrals or earthing impedances may be connected in order to pass the maximum fault current. The earthing system also ensures that no thermal or mechanical damage occurs on the equipment within the substation, thereby resulting in safety to operation and maintenance personnel. The earthing system also guarantees equipotent bonding such that there are no dangerous potential gradients developed in the substation. In designing the substation, three voltages have to be considered these are: 1. Touch Voltage This is the difference in potential between the surface potential and the potential at earthed equipment whilst a man is standing and touching the earthed structure. 2. Step Voltage This is the potential difference developed when a man bridges a distance of 1m with his feet while not touching any other earthed equipment. 3. Mesh Voltage This is the maximum touch voltage that is developed in the mesh of the earthing grid.
  12. 12. 11 SubstationEarthingCalculation Methodology Calculations for earth impedances, touch and step potentials are based on site measurements of ground resistivity and system fault levels. A grid layout with particular conductors is then analyzed to determine the effective substation earthing resistance, from which the earthing voltage is calculated. In practice, it is normal to take the highest fault level for substation earth grid calculation purposes. Additionally, it is necessary to ensure a sufficient margin such that expansion of the system is catered for. To determine the earth resistivity, probe tests are carried out on the site. These tests are best performed in dry weather such that conservative resistivity readings are obtained. Earthing Materials :- 1. Conductors Bare copper conductor is usually used for the substation earthing grid. The copper bars themselves usually have a cross-sectional area of 95 square millimeters, and they are laid at a shallow depth of 0.25-0.5m, in 3-7m squares. In addition to the buried potential earth grid, a separate above ground earthing ring is usually provided, to which all metallic substation plant is bonded. 2. Connections Connections to the grid and other earthing joints should not be soldered because the heat generated during fault conditions could cause a soldered joint to fail. Joints are usually bolted. 3. Earthing Rods
  13. 13. 12 The earthing grid must be supplemented by earthing rods to assist in the dissipation of earth fault currents and further reduce the overall substation earthing resistance. These rods are usually made of solid copper, or copper clad steel. Switchyard Fence Earthing The switchyard fence earthing practices are possible and are used by different utilities. These are: a) Extend the substation earth grid 0.5m-1.5m beyond the fence perimeter. The fence is then bonded to the grid at regular intervals. b) Place the fence beyond the perimeter of the switchyard earthing grid and bond the fence to its own earthing rod system. This earthing rod system is not coupled to the main substation earthing grid. CONDUCTORSUSEDIN SUBSTATIONDESIGN An ideal conductor should fulfill the following requirements: a) Should be capable of carrying the specified load currents and short time currents. b) Should be able to withstand forces on it due to its situation. These forces comprise self-weight, and weight of other conductors and equipment, short circuit forces and atmospheric forces such as wind and ice loading. c) Should be corona free at rated voltage. d) Should have the minimum number of joints. e) Should need the minimum number of supporting insulators. f) Should be economical.
  14. 14. 13 The most suitable material for the conductor system is copper or aluminums. Steel may be used but has limitations of poor conductivity and high susceptibility to corrosion. In an effort to make the conductor ideal, three different types have been utilized, and these include: Flat surfaced Conductors, Stranded Conductors, and Tubular Conductors. OVERHEADLINETERMINATIONS :- Two methodsare used to terminate overheadlines at a substation. a) Tensioning conductors to substation structures or buildings b) Tensioning conductors to ground winches. The choice is influenced by the height of towers and the proximity to the substation. The following clearances should be observed: VOLTAGE LEVEL MINIMUM GROUND CLEARANCE
  15. 15. 14 less than 11kV 6.1m 11kV - 20kV 6.4m 20kV - 30kV 6.7m greater than 30kV 7.0m  STANDARD SIZES OF CONDUCTOR FOR LINES OF VARIOUS VOLTAGES The following sizeshave now been standardized by CEA for transmission lines of different voltages:- 1. For 440 KV Lines Twin 'Moose' ACSR having 7-Strands of steel of dia 3.53 mm and 54-Strands of Aluminum of dia 3.53 mm. 2. For 220 KV Lines 'Zebra' ACSR having 7-strand of steel of dia 3.18 mm and 54- Strands of Aluminum of dia 3.18 mm. 3.For132 KV Lines 'Panther' ACSR having 7-strands of steel of dia 3.00 mm and 30-Strands of Aluminum of dia 3.00 mm. Clearance in accordance with voltage value
  16. 16. 15 -: ISOLATOR :-  Mainly the isolator is connected after the circuit breaker .The circuit breaker is trip due to the fault, or when suddenly a heavy current is flows , it means that the current will not flow after the breaker ,but small amount of current is flows inner circuit.  For making this current total zero the isolator is open and isolator is connected to ground so all inner current will grounded. This is the main work of isolator and other equipments are saved.
  17. 17. 16  Isolatorsare two types :- 1- Bus Isolator- the isolator is directly connected with main bus. 2- Line Isolator- the isolator is situated at line side of any feeder. -: INSULATOR :-
  18. 18. 17  The insulator serve two purpose. They support the conductor (bus bar ) and confine the current to the conductor . The most commonly used material for the manufacturerof insulatoris porcelain .  But the most wild use of insulatoris to insulate the support or tower from the electric current .These are several type of insulators (e.g. pin type ,suspension type , post insulator ,shackle insulator etc.) and their use in the substation will depend upon the service requirement .For example post insulator is used for bus bars can directly bolted to the cap. -: TRANSFORMER :-
  19. 19. 18  A transformer is an electrical device that transfers energy betweentwo ormore circuits through electromagneticinduction.  TypesofTranformer:-  Step Up Transformer  Step Down Transformer  Power Transformer  Distribution Transformer  IdealTransformer :-  Its primary and secondary winding resistances are negligible .  Its leakage flux and leakage inductanceare zero There are no losses due to resistance, hysteresis and eddy currents.  The efficiency is 100 percent.
  20. 20. 19  In case ofideal transformer Np*Ip =Ns*Is  Idealtransformerasacircuitelement PROTECTION OF TRANFORMER :-
  21. 21. 20 CONSERVATOR:- As the temperature of oil increases or decreases during operation there is corresponding rise or fall in volume. To account for this an expansion vessel is connected to the transformer tank.  The conservator has got a capacity between minimum and maximum oil level equal to 10% of the total oilin transformer.  The conservator is provided with magnetic oil level gauge on one of the end covers which has a low oil level alarm. The ideal indicates empty 1/4,30.c, ¾ and fulloillevel. RADIATOR:-
  22. 22. 21  Owing the transport limitation and considering possible transient damages. Large transformer are provided with detachable radiators with radiator value.  At the time of dispatch these radiators are detach and sent separately keeping the valve in positionon tank flange. The valve blanking plate is to removed only when the radiators is ready formounting onflanges. On removal ofblanking plate a small quantity ofoilwhich may have collected between valve and blanking platewillseep out.  The radiator section is made of 1mm thick cold rolled carbon steel sheets. The distance between each section is 50mm. The number of section per radiators and the number of radiators per transformer will depend upon cooling requirement of that transformer. BUCHHOLZ RELAY :-
  23. 23. 22  The transformer is fitted with double float buchholz relay.  It is fitted in the feed pipe from conservator to tank and it is provided with two sets of mercury contacts.  The device comprises with the cast iron housing containing the hinged floats, one in upper part and other in lower part . Each float is fitted with mercury switches, leads of which are connected to terminal box for external connection.  An arrow in cast on the housing to indicate the direction of conservator. The operation of buchholz relay should be tested before installing by injecting air at the lowest cock.  It is connected to the protection circuit to give an early alarm in case of gas collection and to disconnection of transformer from supply in case the sever fault inside the transformer. SILICA GEL BREATHER :-
  24. 24. 23  When transformer is loaded or unloaded the oil temperature inside the transformer is rise or falls. Accordingly the volume of air is changes by either by sucking in or pushing out . This transformer phenomena is called BREATHING of transformer.  The air which I being sucked in container may have foreign impurities and humidity which changes dielectric stray of transformer oil . Hence it is necessary that the air entering into the transformer is free room moisture and foreign impurities. The breather is connected to an outlet pipe of conservator vessel and the air which is sucked by the transformer is made to pass through silica gel breather to dehumidify the air and remove the foreign impurities . The air which is pass through the gel is pass first to oil compartment of the breather. The oil removes all foreign impurities which enter into the gel compartment. Silica gel breather keeps all the properties of oil constant so transformer has a long life.
  25. 25. 24 COOLING :-  When a transformer is in operation the heat is generated due to iron loss in winding and core loss. The process of minimise this heat is called cooling. AIR NATURAL COOLING :-  In a dry type self-cooled transformer, the natural circulationof surrounding air is used for cooling. This process of cooling is satisfactory for low voltage small transformer up to few KVA. AIR BLAST COOLING :-  It is similar to natural cooling with an addition that continuous blast of filtered cooled air is forced through the core and winding for better cooling. A fan producesthe blast. ForcedOil withCirculatingWaterCooling :-
  26. 26. 25  In this type of system heat exchanger is used for cooling the transformer . This system is used for large rating of power transformer.
  27. 27. 26 -:EQUIPMENT OFSUB-STATION:-  WAVETRAP:-  Wave trap unit is inserted between bus bar and connection of coupling capacitor to the line. It is parrel tuned circuit comprising L and C. It has low impedance to 50 Hz and high impedance to carrier frequencies.  Thus coupling capacitor allows carrier frequencies signals to enter the carrier equipment, but does not allows 50Hz power frequency current to enter the carrier equipment. This unit prevents the high frequencies signal from entering the neighbouring line, and the carrier current to flow only in the protected line for communication between different substation. LIGHTING ARRESTER :-
  28. 28. 27  Lighting arresters are protective device for limiting surge voltages due to lighting strikes or equipment faults or other events, to prevent damage to equipment and disruption of service. This type of equipment also called surge arresters.  Lighting arresters are installed on many different pieces of
  29. 29. 28 equipment such as power poles and towers, power transformer, circuit breaker, bus structure, and steel superstructurein substation. CURRENT TRANSFORMER:-  A current transformer (CT) is used for measurement of alternating electric currents. Current transformers, together with voltage (or potential) transformers (VT or PT), are known as instrument transformers. When current in a circuit is too high to apply directly 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 isolates the measuring instruments from what may be very high voltage in the monitored circuit. Current
  30. 30. 29 transformers are commonly used in metering and protective relays in the electrical power industry.  They are commonly used in metering and protective relaying in the electrical power industry where they facilitate the safe measurement of large currents, often in the presence of high voltages.  The current transformer safely isolates measurement and control circuitry from high voltage typically present on the circuit being measured. The CT acts as constant current series device with an apparent power burden a fraction of that of high voltage primary circuit.  Common secondary's are 1 or 5 amperes . For example; a 400:1 CT would provide an output current of 1 ampere when the primary was passing 400 amperes.  Current transformers used in metering equipment for three-phase 400-ampere electricity supply  Like any other transformer, a current transformer has a primary winding, a magnetic core and a secondary winding. The alternating current in the primary produces an alternating magnetic field in the core, which then induces an alternating current in the secondary winding circuit. An essential objective of current transformer design is to ensure the primary and secondary circuits are efficiently coupled, so the secondary current is linearly proportional to the primary current.  The most common design of CT consists of a length of wire wrapped many times around a silicon steel ring passed 'around' the circuit being measured. The CT's primary circuit therefore consists of a single 'turn' of conductor, with a secondary of many tens or hundreds of turns. The primary winding may be a permanent part of the
  31. 31. 30 current transformer, with a heavy copper bar to carry current through the magnetic core. Window-type current transformers (aka zero sequence current transformers, or ZSCT) are also common, which can have circuit cables run through the middle of an opening in the core to provide a single-turn primary winding. When conductors passing through a CT are not centered in the circular (or oval) opening, slight inaccuracies may occur. POTENTIALTRANSFORMER:-  A voltage transformer theory or potential transformer theory is just like a theory of general purpose step down transformer. Primary of this transformer is connected across the phase and ground. Just like the transformer used for stepping down purpose, potential transformer i.e. PT has lower
  32. 32. 31 turns winding at its secondary. The system voltage is applied across the terminals of primary winding of that transformer, and then proportionate secondary voltage appears across the secondary terminals of the PT.  The secondary voltage of the PT is generally 110 V. In an ideal potential transformer or voltage transformer, when rated burden gets connected across the secondary; the ratio of primary and secondary voltages of transformer is equal to the turns ratio and furthermore, the two terminal voltages are in precise phase opposite to each other. But in actual transformer, there must be an error in the voltage ratio as well as in the phase angle between primary and secondary voltages.  Potential transformer is designed for monitoring single - phase and three - phase line voltages in power metering application. The primary terminals can be connected either in line - to -line or in line - to - neutral configuration.  A potential Transformer is a special type of transformer that allows meters to take reading from electrical service connections with higher voltage than the meter is normally capable of handling without at potential transformer .  Potential transformer has an accuracy of +_ 5% from 0 to 130% of their rated voltage. CIRCUITBREAKER:-  Circuit breaker is mechanical device which is so designed by which circuit normal current fault position will be on and off .They are used for high capacity. A circuit breaker can make or break a circuit either manually or automatically under all condition viz. no load and short circuit condition .
  33. 33. 32 Typesofcircuitbreaker is :-  Oil circuit breaker: In oil circuit breaker the fixed contact and moving contact are immerged inside the insulating oil. Whenever there is a separation of electric current carrying contacts in the oil, the arc in circuit breaker is initialized at the moment of separation of contacts, and due to this arc the oil is vaporized and decomposed in mostly hydrogen gas and ultimately creates a hydrogen bubble around the arc. This highly compressed gas bubble around the arc prevents re-striking of the arc after electric current reaches zero crossing of the cycle.  AIR CIRCUIT BREAKER :
  34. 34. 33 For interrupting arc it creates an arc voltage in excess of the supply voltage. Arc voltage is defined as the minimum voltage required maintaining the arc. This circuit breaker increases the arc voltage by mainly three different ways: It may increase the arc voltage by cooling the arc plasma. As the temperature of arc plasma is decreased, the mobility of the particle in arc plasma is reduced, hence more voltage gradient is required to maintain the arc. It may increase the arc voltage by lengthening the arc path. As the length of arc path is increased, the resistance of the path is increased, and hence to maintain the same arc electric current more voltage is required to be applied across the arc path. That means arc voltage is increased. Splitting up the arc into a number of series arcs also increases the arc voltage.  Sulphur Hexa Fluoride circuit breaker :
  35. 35. 34 In such circuit breaker, sulphur hexafluoride (SF6) gas is used as the arc quenching medium. The SF6 is an electronegative gas and has a strong tendency to absorb free electrons. It consists of fixed and moving contacts. It has chamber, contains SF6 gas. When the contacts are opened, the mechanism permits a high pressure SF6 gas from reservoir to flow towards the arc interruption chamber. The moving contact permits the SF6 gas to let through these holes. These circuit breakers are availabl for the voltage ranges from 33KV to 800KV and even more.  Vacuum circuit breaker :
  36. 36. 35 Vacuum circuit breakers are circuit breakers which are used to protect medium and high voltage circuits from dangerous electrical situations. Like other types of circuit breakers, vacuum circuit breakers literally break the circuit so that energy cannot continue flowing through it, thereby preventing fires, power surges, and other problems which may emerge. The operation of opening and closing of electric current carrying contacts and associated arc interruption take place in a vacuum chamber in the breaker which is called vacuum interrupter. CONTROLPANEL:-
  37. 37. 36  This is the main part of the substation. We plant it outside the switchyard. All the equipment which is install inside the switchyard is connected to the control panel by a underground cable. These cable are connected to the measuring devices like as voltmeter and ammeter of high rating.  This control panel also consists a different type of relays like as differential, earth fault, auxiliary etc. control panel gives all the correct reading for example when a line is come in switch yard is connected to CVT. This CVT gives an exact value of incoming voltage on the control panel, If any fault is occurs, the relay is trip and we can see it on control panel and except it control panel gives the rating of all feeders and temperature of oil and winding in the transformer. BATTERYROOM:-
  38. 38. 37  This is the room, which consist DC batteries. There are 55 DC cell of 2 Volt each. These cells are connected in series, so it will give total of 110V. This 110VDC Supply is used for operating the controlpanel, when the AC supply is off. This 110V DC voltage is also supplied to circuit breakers for operating; this supply is used when AC is off. We use this supply as a secondary supply. It means that this DC voltage is used when the AC is interrupted. -: CONCLUSION :-  Now from this report one can conclude that electricity plays an
  39. 39. 38 important role in our life. At the end of the training, I came to know about the various parts of substations and how they are operated. Also I learnt about how transmission is done in various parts of Uttarpradesh.  As evident from the report, a substation plays a very important role in the transmission system. That’s why various protective measures are taken to protect the substations from various faults and its smooth functioning. Power Transmission Corporation of Uttarpradesh Limited takes such steps so that a uniform and stable supply of electricity can reach in every part of this state.
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