Anearthing switch, which is also namedground switch, is a mechanical switching device used to intentionally ground a circuit.
Under abnormal conditions (such as short circuit), the earthing switch can carry the specified rated short circuit current and the corresponding peak current within a specified time; However, under normal working conditions, it is not required to carry rated current.
The earthing switch and the disconnecting switch are often combined into a single device. At this time, in addition to the main contact, the isolation switch is also equipped with a earthing switch for grounding one end of the isolation switch after opening. The main contact and earthing switch are usually mechanically interlocked in such a way that the earthing switch cannot be closed when the isolation switch is closed and the main contact cannot be closed when the ground switch is closed.
Earthing switch according to the structure can be divided into open and closed two kinds. The conductive system of the former is exposed to the atmosphere with a earthing switch similar to the isolation switch, and the conductive system of the latter is enclosed in a charge SF. Or oil and other insulating media.
The earthing switch needs to close the short circuit current, and must have a certain short circuit closing ability and dynamic and thermal stability. However, 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 knife is usually connected to the ground point through the current transformer. The current transformer can give a signal for relay protection.
The earthing switches of various structures are divided into single pole, double pole and three pole. The single pole is used only in neutral grounded systems, while the double and triple poles are used in neutral ungrounded systems and share a single operating mechanism for operation.
Post time: Aug-15-2023