A grounding switch is a mechanical grounding device designed to discharge static electricity from equipment and circuits under maintenance and to ensure the personal safety of maintenance personnel during power-off repairs.

It can withstand current for a limited time under abnormal conditions (such as short circuits) but does not carry load current under normal conditions. It is typically an integral part of a disconnect switch.

I. Function of an Earthing Switch

1. Ensuring Maintenance Safety: By reliably grounding equipment to discharge residual charges and neutralize induced voltages, the system maintains a zero-potential state, eliminating the risk of electric shock for maintenance personnel.

2. Limiting fault voltage: Works in conjunction with surge arresters to divert excess charge generated by lightning strikes and switching overvoltages, thereby protecting equipment insulation from damage.

3. Auxiliary Debugging and Troubleshooting: Establish controllable ground fault points to simulate faults for testing the reliability of relay protection devices. This method can also be used for post-maintenance insulation testing of power lines.

II. Earthing Switch Application Scenarios

1. Line maintenance safety grounding: Ensures equipment and personnel safety during maintenance.

2. Disconnecting Induced Electricity: Handling induced voltage and current after power outages on shared towers or adjacent parallel overhead lines.

3. Closing Short-Circuit Current: Suitable for various voltage and current conditions, capable of closing rated short-circuit closing currents.

4. Maintenance and Testing Support: Used for power system fault simulation and line insulation condition testing.

III.Types of Earthing Switchs

1. Maintenance Grounding Switch: Primarily used to establish a safety grounding loop during equipment maintenance, with operation rhythms aligned to operational procedures.

2. Rapid-Closing Fault Grounding Switch: Features rapid response capability, enabling swift closure during system ground faults to limit fault currents and overvoltages.

From an application perspective, grounding switches cover all voltage levels in power systems. In conventional open-type substations, they are often installed alongside disconnectors on the line side and busbar side.

In advanced power equipment such as GIS (Gas-Insulated Switchgear) and HVDC (High-Voltage Direct Current) converter stations, built-in grounding switches are critical components for ensuring internal maintenance safety and limiting internal overvoltages.