Electrical Substation, How does it work?
The electrical power system is AC i.e. Electrical power is generated, transmitted and distributed in the form of alternating current. Substations serves as source of energy supply for area of distribution in which these are located. The main functions are to receive energy transmitted at high voltage from the generating stations, reduce the voltage to a value appropriate for local distribution and provide facilities for switching. Some substations are simply switching stations where different connection between various transmissions lines are made others are converting substations which either convert AC into DC or vice versa or convert frequency from higher to lower or vice versa. Substations have some additional functions they provide points where safety devices may be installed to disconnect equipment or circuit.
Definition of substation
The Assembly of apparatus which is used to change electrical voltage frequency and power factor of electrical supply is called a substation sub stations are important part of power system there are some following important. Which must be kept in mind while playing out a substation
– It should be located at proper site as far as possible
– It should be located at the centre of gravity of load
– It should provide safe and reliable arrangement for safety consideration must be given to the maintenance of regulation clearance.
-It should be easily operated at maintained it should involve minimum capital cost.
Classifications of substation
The substations may be classified in numerous base such as on the basis of nature of duties, service rendered, operating voltage, design importance.
Classifications of substations on the basis of nature of duties:
Substations on the basis of nature of duties may be classified into the following 3 category.
1. Step up or primary substation: Step up primary substations are usually associated with generating stations which generates voltage which is usually low its step up to primary transmission voltage so that huge blocks of power can be transmitted over long distance to the load Centre economically.
2. Primary grid substation: are located at suitable load centre along the primary transmission lines in these substations the primary transmission voltage is stepped different suitable secondary voltage.
3. Step down or distribution substation: Such sub stations are located at the lowest and We’re the subs stations primary distribution board is easy step to secondary distribution bol test.
Classification of substations on the basis of service render:
On the basis of service renders the substations maybe classifieds into the following three categories
1. Transformer substations: Transformer are installed on such substations to transform the power from one level to another level.
2. Switching substations: such substations are made for switching operations of power lines without transforming the voltage.
3. Converting substations: such substations are made for converting AC to DC or vice versa converting frequency from higher to lower or vice versa.
Classifications of substations on the basis of operating voltage:
The sub-stations on the basis of operating voltage may be classified into following three categories
1. High voltage substations: These substations involve voltage between 11 KV and 66 KV.
2. Extra high voltage substations: These substations involved voltage between 132 KV and 400 KV
3. Ultra high voltage substations: These substation operates on voltage above 400 KV.
Classifications of substations on the basis of importance:
On the basis of importance, transformers are classified into flowing categories.
1. Grid substations: these are the stations from where bulk power is transmitted from one point to another point in the grid.
2. Town substations: These substations stepped down the 33/11KV for further distribution in the towns and any failure in such substitution result in failure of supply for whole of the town.
Classification of substations on the basis of design:
1. Indoor types substations: In such substations the operators is installed in the substation building.
2. Outdoor substation: In such substitutions the operators is installed outside the substation building.
Equipment used in a transformer substation :
Generally a transformer substations has the following main equipments
1. Bus Bar: When a number of lines operating at the same voltage have to be directly connected electrically, busbar are used as the common Electrical government component. Bus bar are copper or aluminium bars and operates at constant voltage.
2. Insulators: insulators are used to provide insulation in the electric substation. They support the conductors and canfine the current to the conductor.
3. Isolating switch: In substation it often desired to disconnect a part of substations for general maintenance and repair this is accomplished by an isolating switch or isolator.
4. Power transformer: A power transformer is used in substations to step up or step down the voltage.
5. Circuit breaker: A circuit breaker is an equipment which can open or close a electric circuit under normal as well as faulty condition. It is so designed that it can we operate manually under normal conditions and automaticaly faulty conditions.
6. Instrument Transformers: The lines in substations operates at Higher voltage and carry current of thousands of ampere. The measuring instrument and protective devices are designed for low voltage and current. They will not work satisfactorily at higher voltage and current. This difficulty is overcome by installing instrument Transformer on the power line. There are two types of instrument transformer
– current transformer
– voltage transformer
7. Metering and indicating instruments: There are several metering and indicating instruments installed in a substation to maintain watch over the circuits quantities.