Equipment in a 132 KV substation
The equipment required for a transformer substation depends upon the type of substation, service requirement and the degree of protection desired. 132KV substation has the following major equipment.
When a number of lines operating at the same voltage have to be directly connected electrically, busbar are used, it is made up of copper or aluminum bars (generally of rectangular X-Section) and operate at constant voltage.
There may be double line in the bus so that if any fault occurs in the one, the other can still have the current and the supply will not stop. The two lines in the bus are separated by a little distance by a conductor having a connector between them.
This is so that one can work at a time and the other works only if the first is having any fault.
The insulator serves two purpose. They support the conductor (or busbar) and confine the current to the conductor. The most commonly used material for the manufactures of insulators is porcelain.
There are several type of insulator (i.e. pine type, suspension type etc.) and their use in substation will depend upon the service requirement.
Post insulators are used for the busbars. A post insulator consists of a porcelain body, cast iron cap and flanged cast iron base. The whole cap is threaded so that busbars can be directly bolted to the cap. When the line is subjected to a greater tension, strain insulators are used.
When tension in line is exceedingly high, two or more strings are used in parallel.
In a power substation, it is always desired to disconnect a part of the system for general maintenance and some repairs. This is accomplished by an isolating switch or isolator.
An isolator is originally a knife switch and is design to often open a circuit under no load. Isolator switch operates only when the line is which they are connected to carry no load.
This may batter the supporting insulators and may even cause a fatal accident to the operator, particularly in the high voltage circuit.
The operating principle is manual plus one of the following:
- Electrical Motor Mechanism
- Pneumatic Mechanism
Isolators cannot be opened unless the Circuit Breakers are opened. Circuit Breakers cannot be closed until isolators are closed.
A circuit breaker is an equipment, which can open or close a circuit under normal as well as fault condition. These circuit breaker breaks for a fault which can damage other instrument in the station.
Whenever a fault occurs trip coil gets energized, the moving contacts are pulled by some mechanism and therefore the circuit is opened or circuit breaks.
When circuit breaks an arc is stack between contacts, the production of arc not only interrupts the current but generates enormous amount of heat which may cause damage to the system or the breaker itself.
Therefore the main problem in a circuit breaker is to extinguish the arc within the shortest possible time so that the heat generated by it may not reach a dangerous value.
|Title:||132 KV substation basic training for students – Rahul Saha (JIS School of Polytechnic)|
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