Presentation On Summer Training from UPPTCL 132/33 KV Sub-Station Minto Park, AllahabadSUBMITTED BY :-
SHAILESH YADAV Mob.No.- 9415147950Emailemail@example.com
India has been divided into five regions for power system planning and operation. These regions are the Northern region, Western region, Eastern region and North-eastern region. Present almost 70% of the population is enjoying the fruits of electricity. The present day electricity power system is AC i.e. electric power is generated, transmitted and distributed in the form of alternating current. The electric power is produced at the power station, which are located at favourable place, generally quite away from the consumers1.Transformer:
A transformer is an electrical device that transfers energy between two or more circuits through electromagnetic induction.
1.2Types Of Transformer:
Step Up Transformer Step Down Transformer Power Transformer Distribution Transformer
Its primary and secondary winding resistances are negligible . Its leakage flux and leakage inductance are zero . There are no losses due to resistance, hysteresis and eddy currents. The efficiency is 100 percent.
In case of ideal transformer Np*Ip = Ns*Is
Ideal transformer as a circuit element :
2.PROTECTION AND COOLING EQUIPMENT:
2.1CONSERVATOR: 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 oil in 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, and full oil level.
2.2 RADIATOR 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 position on tank flange. The valve blanking plate is to removed only when the radiators is ready for mounting on flanges. On removal of blanking plate a small quantity of oil which may have collected between valve and blanking plate will seep 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
2.3 BUCHHOLZ RELAY: 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.
2.4 SILICA GEL BREATHER: 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.
2.5 MARSHALLING BOX: It has two indicators which indicate the temperature of oil and winding of main tank, known as OTI and WTI. If the temperature of oil or winding exceeds the specified value , relay operates to sounds an alarm. If there is further increase in temperature then relay completes the trip circuit open the circuit breaker controlling the transformer.
2.6 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.
2.6.1 AIR NATURAL COOLING
In a dry type self-cooled transformer, the natural circulation of surrounding air is used for cooling. This process of cooling is satisfactory for low voltage small transformer up to few KVA.
2.6.2 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 produces the blast.
2.6.3 Forced Oil with Circulating Water Cooling:
In this type of system heat exchanger is used for cooling the transformer .This system is used for large rating of power transformer.
3. EQUIPMENT OF SUB-STATION:
3.1 LIGHTING ARRESTER:
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 equipment such as power poles and towers, power transformer, circuit breaker, bus structure, and steel superstructure in substation.
3.2 WAVE TRAP:
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 substations.
3.3 CURRENT TRANSFORMER:
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.
3.4 POTENTIAL TRANSFORMER:
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.
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.
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 manufacturer of insulator is porcelain .But the most wild use of insulator is 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.
3.7 CIRCUIT BREAKER:
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 .
Types of circuit breaker is :
1. Low voltage air circuit breaker2. oil circuit breaker3. Sulphur Hexa Fluoride circuit breaker4. Air blast circuit breaker5. vacuum circuit breaker
3.8 CAPACITOR BANK:
The load on the power is varying, being high during morning and evening and low at other times. During low load period, supply voltage is increased which increases the magnetization current, thi