Substation


Substation

A Substations generally have switching, protection transformer and control equipments. A substation performs no. of function in electrical systems. Substations transform voltage from high to low level, or the reverse, frequency conversion, PF improvement 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.
In a large substation, Circuit Breaker are used to interrupt any short circuits or overload currents that may occur on the network.

A substation may include transformer to change voltage levels between high transmission voltages and lower distribution voltages, or at the interconnection of two different transmission voltages.

Substations may be owned and operated by an electrical utility, or may be owned by a large industrial or commercial customer.
Substations may be on the surface in fenced enclosures, underground, or located in special purpose buildings. Some  Buildings may have several indoor substations. Indoor substations are usually found in urban areas.


Types
Transmission substation
A transmission substation connects two or more transmission lines. A transmission station may have transformer to convert between two transmission power factor improvement devices such as capacitors, static VAR/synchronous capacitor and equipment such as phase control transformer to control power flow between two adjacent power systems.
Distribution substation
A distribution substation transfers power from the transmission system to the distribution system. The distribution station reduces voltage to a level suitable for local distribution at 440V, 3 Phase.


A sub-station may be called upon to change voltage level or improve power factor or convert a.c. power into d.c. power etc. According to the service requirement, sub-stations may be classified into :

·       Switching sub-stations. These sub-stations do not change the voltage level i.e. incoming and outgoing lines have the same voltage. However, they simply perform the switching operations of power lines.

·       Transformer sub-stations. Those sub-station change the voltage level of electric supply are called transformer sub-stations. These sub-stations receive power at some voltage and deliver it at some other voltage

·       Power factor correction sub-stations. Those sub-stations which improve the power factor of the system are called power factor correction sub-stations. These sub-stations generally use synchronous condensers as the power factor improvement equipment.

·       Converting sub-stations. Those sub-stations which change a.c. power into d.c. power are called converting sub-stations. These sub-stations receive a.c. power and convert it into d.c. power. 

·        Frequency changer sub-stations. Those sub-stations which change the supply frequency are known as frequency changer sub-stations.

·        Industrial sub-stations. Those sub-stations which supply power to individual industrial concerns are known as industrial sub-stations.



Equipments used in a substation


Lighting arrestor

Instrument transformer
Bus bar
Power transformer
Isolator 
Circuit breaker
Batteries 
Capacitor..etc

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