Isolating Switch
The definition of disconnector is as follows:
When in the open position, there is an insulation distance between the contacts that meets the specified requirements and an obvious disconnection mark; when in the closed position, it is a switching device that can carry the current under normal circuit conditions and the current under abnormal conditions (such as short circuit) within a specified time
When the circuit current is "very small", or when the voltage between the two terminals of each pole of the disconnector does not change significantly before and after closing and opening, the disconnector has the ability to close and open the circuit.
Function:
Used to disconnect or connect the circuit without load current, forming a visible electrical isolation breakpoint.
Not used to cut off load current or fault current (no arc extinguishing ability), only to ensure that the circuit is physically disconnected during maintenance.
Purpose:
Isolate the power supply during maintenance to ensure safety;
Used with circuit breaker (break the circuit breaker first, then operate the isolating switch).
Features:
Visible break, clear mechanical indication;
Usually without arc extinguishing device.
Earthing Switch
The definition of grounding switch is as follows:
A mechanical switching device used to ground a circuit, which can carry a specified abnormal current for a specified time under abnormal conditions (such as short circuit); but is not required to carry current under normal circuit conditions.
Function:
Directly ground the disconnected line or equipment to release residual charge and prevent electric shock or induction shock in case of misoperation.
It is divided into maintenance grounding switch (manual operation) and fast grounding switch (can close short-circuit current).
Purpose:
Ensure reliable grounding of equipment during maintenance;
In GIS (gas insulated switchgear), it is often linked with the disconnector.
Features:
Usually does not have the ability to break current (unless specially designed);
Before operation, it must be confirmed that the line is de-energized.
Summary
| Features | Isolating switch | Earthing switch |
|---|---|---|
| Main functions | Electrical isolation (visible break) | Mandatory grounding (to ensure safety) |
| Operation time | Operate when there is no load | Operate after confirming that there is no power |
| Arc extinguishing capability | None | Generally none (except for fast earthing switch) |
| Interlocking relationship | May be interlocked with circuit breaker | Often interlocked with isolating switch |
Common combinations
Three-position disconnector: The functions of the disconnector and the grounding switch are integrated into one device, divided into three positions: "disconnection-disconnection-grounding" to avoid misoperation.
In GIS: The disconnector and the grounding switch are usually designed as a linkage mechanism to ensure the correct operation sequence.
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