The grounding switch is a kind of mechanical grounding device that releases the static electricity of the equipment and circuit under maintenance and the personal safety of the maintenance personnel to ensure the power failure maintenance. It can withstand a certain amount of current under abnormal conditions, but does not pass the load current under normal conditions. It is usually part of the disconnector.
Earth switch in switchgear and disconnectors are often combined into one unit. In this case, the isolating switch has a grounding switch in addition to the main contact for grounding one end of the isolating switch after opening. The main contact and grounding switch typically achieve mechanical interlocking in such a way that the grounding switch cannot be closed when the isolating switch is closed and the main contact cannot be closed when the grounding switch is closed.
The earthing switch can be divided into open type and closed type according to the structure. The former's conductive system is exposed to a grounded knife gate similar to an isolating switch in the atmosphere, and the latter's conductive system is enclosed in a sf. Or in an insulating medium such as oil.
The grounding switch needs to close the short-circuit current, and must have a certain short-circuiting capability and dynamic and thermal stability. But it does not need to break the load current and short-circuit current, so there is no arc extinguishing device. The lower end of the blade is usually connected to the ground point via a current transformer. Current transformers give signals for relay protection.
Grounding switches of various construction types are divided into single pole, double pole and three poles. The single pole is only used for the neutral point grounding system, and the bipolar and three poles are used for the neutral point ungrounded system, sharing a single operating mechanism for operation.