What is an isolating switch?

Isolating switch, commonly known as "knife switch", is one of the most widely used high-voltage switchgear. It generally refers to high-voltage isolating switch, i.e. isolating switch with rated voltage of 1kV and above, usually referred to as isolating switch, which play an isolating role in the circuit. Its working principle and structure are relatively simple, but due to the large amount of use and high reliability requirements of high-voltage power, it has a great impact on the design, establishment and safe operation of substations and power plants. The main feature of the isolating switch is that it has no arc-extinguishing ability and can only open and close the circuit without load current. The isolating switch is used at all levels of voltage to change the circuit connection or isolate the line or equipment from the power supply. It has no current breaking capacity, and can only be operated after the line is disconnected with other equipment.

Let's elaborate on its three functions:

1. Isolated power supply

Between the parts that need to be repaired and other live parts, use the isolating switch to form a large enough visible air insulation interval. If necessary, a grounding switch shall be attached to the isolating switch for grounding during maintenance.

2. Switching operation

Use isolating switch to switch electrical equipment or lines from one group of buses to another group of buses.

In case of power failure, the circuit breaker, load side isolating switch and power side isolating switch must be operated in sequence, and the power transmission operation is opposite; Before operating the isolating switch, check the opening position of the circuit breaker. Before closing the circuit breaker for power transmission, check the closing position of the isolating switch to prevent pulling and closing the isolating switch with load.

3. Opening and closing small current

The isolating switch has no arc-extinguishing device and cannot switch or close the load current and short-circuit current. However, it has certain ability to open and close small current.