(i) Earth Switch
It’s function is to discharge the ground capacitance when line is open circuited for maintenance purpose by isolator.) Earthing switch is inter - locked with isolator from the safety point of view
It sense the faults & gives signal to trip circuit of C.B. to open. There are different types of relay e.g. Earth fault relay, Phase to Phase fault relay, Thermal relay etc.
iii) Lightning Arrester: -
It is provided for protection of substation, transformer against lightning stroke .It is connected in between line and ground at the starting point of substation. Under normal condition it acts as an insulator.
iv) Auxiliary Transformer : -
Its function is to step down the input voltage (11 KV) to distribution voltage (3-ph, 4wire, 400V) to give supply to control room, area lighting, staff quarters etc,