<p style="text-align:justify"><span style="font-size:14px">Control supply for controlling (making ON and OFF) breakers and isolators and auto control of breakers through protective gear is always d. c., as in case of station supply failure, control is not lost. This d. c. supply (usually 220 V d. c.) is obtained using rectifier. In all substations there is 11 kV/ 415 V station transformer. This 415 V (230 V phase to neutral) supply is rectified to 220 V d. c. to feed to control circuits.</span></p>