1. Working principle of grounding switch
The grounding switch has the ability to close the short circuit current. After the line grounding fault is removed, the shallow supply current of the fault line is formed by the adjacent running lines. The shallow supply circuit can be eliminated by using the close cooperation of the fast grounding switch, and then the grounding switch can be quickly opened to ensure the success of the line automatic reclosing.
In general, the fast grounding switch is installed on the side of the outgoing line disconnector close to the line, which has two functions: one is to cut off the capacitive current generated by classical induction and the inductive current generated by electromagnetic induction in parallel overhead lines; On the other hand, when creepage occurs on the insulator inside the enclosure or arcing occurs inside the enclosure, the fast grounding switch will quickly ground the main conductive circuit and cut off the fault current through the circuit breaker.
2. Function of grounding switch
Grounding switch is divided into two types, namely maintenance grounding switch and fast grounding switch. The configuration of maintenance grounding switch is set beside the disconnectors on both sides of the circuit breaker, which only plays the role of grounding on both sides of the circuit breaker during maintenance. The fast grounding switch configuration, which is located on the side of the outgoing circuit and the sound insulation switch close to the line, has two functions: 1) opening and closing the capacitance circuit caused by electrostatic induction and current induction generated by electromagnetic induction of parallel overhead lines; ② When the insulator inside the shell has creepage phenomenon or arcing inside the shell, the fast grounding switch will lower the main circuit to fast ground, and cut off the fault current through the circuit breaker.
3. Which positions of high voltage power distribution device need to be equipped with grounding switch
(1) For outdoor AIS power distribution device, in order to ensure the safety of electrical equipment and bus maintenance, grounding switch shall be installed on each bus. The installation quantity of grounding switch shall be calculated and determined according to electromagnetic induction voltage on bus, length of parallel bus and interval distance. For 1000kV bus, at least two sets of grounding switches are preferred.
(2) For AIS power distribution equipment with voltage level of 110kV and above, the disconnectors on both sides of the circuit breaker are close to the circuit breaker side, the line isolating switch is close to the line side, and the transformer incoming line isolating switch is close to the transformer side, and the grounding switch shall be installed. Grounding switch shall be installed at high voltage side of shunt reactor for AIS power distribution device with 110kV and above voltage level.
(3) For double bus connection, the circuit breaker side of two groups of disconnectors connected with bus can share one set of grounding switch.
(4) The configuration of grounding switch of GIS power distribution device shall meet the requirements of operation and maintenance. The electrical equipment, bus bar and outgoing line connected with GIS power distribution device and requiring independent maintenance shall be equipped with grounding switch. In general, the grounding switch on one side of the line and the bus grounding switch of the outgoing circuit shall adopt the fast grounding switch with the ability of closing and stabilizing the current.
(5) When the transformer and GIS power distribution device are connected by gas pipeline bus, the grounding switch shall be set at the transformer side or GIS side