Silicon Carbide Arresters (SIC):
The Non linear lightning arrester basically consists of set of spark gaps in series with the silicon carbide non linear resistor elements. Lightning arresters are connected between the phase conductors and ground. During normal system operating voltage conditions, the spark gaps are non conducting and isolate the high tension (HT) conductors from the ground.
However whenever an overvoltge of magnitude dangerous to the insulation of the apparatus protected occurs ( these over voltages or over surges may be caused due to lightning strikes on the conductors or due to Extra High Voltage (EHV) switching) the spark gap breaks down and allows the high voltage surge current to flow through the ground.