The role and classification of the isolating switch

The isolating switch has no special arc extinguishing device in its structure, and it is not allowed to use it to carry out the pulling or closing operation. When the isolating switch is pulled, the isolation switch must be pulled after the circuit breaker cuts off the circuit; when closing, the isolation switch must be connected first, and then the circuit breaker is used to close the circuit. The main function of the isolating switch is:

1, isolated power supply

When the electrical equipment is out of power, the isolation switch is used to isolate the equipment that needs to be shut down for maintenance, and the power supply is clearly visible to ensure the safety of the workers and equipment.

2, switching operation

The operating state of electrical equipment can be divided into three working states: operation, standby and overhaul. The operation of changing an electrical device from one operating state to another is referred to as a switching operation. For example, in a circuit with double busbar wiring, an isolating switch (called a busbar isolating switch) connected to the busbar can be used to switch the power supply line from one set of busbar power supply to another set of busbars without interrupting the user's power supply.

3, pull, combine no current or small current circuit

Although there is no special arc-extinguishing equipment, the high-voltage isolating switch can cut off the small current during the pulling process. When the moving and static contacts are quickly opened, the arc between the contacts can be extinguished according to the arc-extinguishing principle of rapidly expanding the arc. . Therefore, the high voltage isolation switch allows the following circuits to be pulled and closed:

1) Pulling and closing voltage transformers and arrester circuits;

2) Pulling and closing the busbar and the capacitance current of the device directly connected to the busbar;

3) No-load transformer with pull and combined excitation current less than 2A: general transformer with voltage of 35kV and capacity of 1000kVA and below; voltage of 110kV with transformer of 3200kVA and below.

4) No-load lines with pull-on and combined capacitor currents not exceeding 5A: overhead lines with a typical voltage of 10kV and a length of 5km or less; overhead lines with a voltage of 35kV and a length of 10km or less.

There are many types of isolating switches, which can be classified according to the following methods:

According to the installation location, it can be divided into indoor and outdoor;

According to the movement mode of the knife gate, it can be divided into horizontal rotation type, vertical rotation type and plug-in type;

According to the number of insulators per phase, it can be divided into single column, double column and three column;

According to the characteristics of operation, it can be divided into single pole and three pole type;

According to the presence or absence of the grounding knife gate, it can be divided into a grounded knife gate and a groundless knife gate.