what is Sub-Station,Lighting arrester,single line diagram of a Sub-Station,working of Sub-Station,Classification of Sub-Station

Sub-Station
            The Electrical Sub-Station is the part of a power system in which the voltage is transformed from low to high or high to low for transmission,distribution,transformation and switching.The main components of an electrical Sub-Station are power transformer,circuit breaker,bus-bar,lighting arrester and insulator.
Lighting Arrester
           It is used for the protection of the equipment at the sub-station against travelling waves.It is connected between the line and earth in parallel with the equipment to be protected at the sub-station.
Single Line Diagram of sub-Station



Working of Sub-Station
                 Electricity has to be transmitted over large distances as the place where the power is being generated and the place where it is consumed can be far apart.The electricity is transmitted at very high voltages and low currents to reduce the heat,eddy current and other transmission losses.
                  The sub-station are where the voltages are increased to high value by using step up transformers and after the transmission the are again stepped down for distribution.
                  Sub-stations are normally out doors but in residential areas the substations may be indoors to restrict the humming noise of huge transformers.
Classification of Sub-Station
                The two most important ways of classifying them are according to.
   1-Service requirement.
   2-Construction features.
Service requirement Sub-Station
  • Transformer Sub-Station:-   In this type of sub-station we change the voltage level of electric supply.These sub-stations receive power at some voltage and deliver it at some other voltage with the help of transformer. 
  • Switching Sub-Station:-   In this type of sub-station we do not change the voltage level of incoming and out going lines.They only perform the switching operation of power lines.
  • Power factor correction Sub-Station:-  In this type of sub-station we only improve the power factor of the system.These types of sub-stations are normally located at the receiving end of transmission lines.
  • Converting Sub-Station;-   These sub-stations change a.c power into d.c power.These types of sub-stations receives a.c power and converts it into d.c power.
  • frequency changer Sub-Station:-   These sub-stations use to change the supply frequency.
According to construction features
              According to construction features the sub-stations are classified as.
  • In door Sub-Station:-   For voltage up to 11kv the equipment of the sub-station is installed indoor because of economic consideration.
  • Out door Sub-Station:-   For voltage beyond 66kv equipment is invariably installed out it is because for such voltages,the clearances between conductors and the space required for switches,circuit breakers and other equipment becomes so great that it is not economical to install the equipment indoor.
  • Under ground Sub-Station:-   In thickly populated areas we do not have enough space so under such situation we construct under ground sub-stations.
  • Pole mounted Sub-Station:-    This is an out-door substations with equipment installed over-head on 4 pole structure.

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