I 08 09 Gas Insulated Switchgear Earthing Switches The earthing switch is classified into two types according to its role. ① Device earthing: manually and electrically controlled for maintenance ② Line earthing: controlled at high-speed. It has an input capacity even when the line is energized. For preventing any unforeseen accidents, it is interlocked with associated circuit breaker and disconnecting switches. Busbars Most busbars up to 362kV use three-phase batch tank for reducing the number of parts and installation period. The conductors are automatically connected via the tulip contactor when the housing of the busbars is assembled. The expansion or shrinkage of conductors due to temperature changes can be compensated.
Compartments Current Transformer Current transformer protects the system by sensing any abnormal current in the line and measuring the usual conductive current. Insulation by high-voltage is not required since this is in the enclosure grounded at both ends of the circuit breaker and isolated by the first conductor and SF6 gas. Voltage Transformer Voltage transformer is a small- sized transformer using high- reliable gas insulated winding. It monitors the voltage of the line or the busbar. Voltage transformer is classified into two types: Metering Out Fit (MOF) and general meters. Lightning Arrester The lightning arrester protects the power utilities from overvoltage due to lightnings or surges and prevents the utilities from breakdowns and blackouts. It uses Zine-Oxide Lightning Arrestor (ZLA) which removes the series gap using Zinc Oxide element.