Presentation On

Summer Training from UPPTCL

132/33 KV Sub-Station

Minto Park, Allahabad

SUBMITTED BY :-

SHAILESH YADAV Mob.No.- 9415147950Email-syee050@gmail.com

Introduction

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 consumers

1.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

1.3Ideal 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, ¾

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.

3.5 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.

3.6 INSULATOR:

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 breaker

2. oil circuit breaker

3. Sulphur Hexa Fluoride circuit breaker

4. Air blast circuit breaker

5. 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, this result in the decreased power factor. The

low power factor is mainly due to the fact that most of the load power factor is

highly undesirable as it causes an increases in current, resulting in additional

losses.

It is important to have power factor is closed as close to unity as possible. In

order to improve the power factor some device taking leading power factor

should be connected parallel with the load. One of such device can be a capacitor

bank. The capacitor draws a leading current and partly or completely neutralizes

the lagging reactive component of load current.

Practically the voltage inside the capacitor bank in the 132KV substation is of

33KV.When the voltage inside the capacitor bank is bellow from 33.5KV the

capacitor bank operated and increased the voltage unto the desired level. If the

voltage is greater than 36.1KV the capacitor bank is of.

Capacitor bank accomplishes following operation

I. To supply reactive power

II. Increase terminal voltage

III. Improve power factor

3.9 CONTROL PANEL:

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.

3.10 BATTERY ROOM :

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 110V DC Supply is used for operating the control panel, 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.