The opening and closing principle of circuit breaker

The opening and closing principle of circuit breaker

The control of the circuit breaker in the high and low voltage switchgear is to control its closing and opening. According to the control location, there are two kinds of control: local control and centralized control. In the vicinity of the circuit breaker, the manual operation mechanism of the circuit breaker is operated by hand or the button control is adopted (through electromagnet or motor) to complete the task of closing and opening, which is the local operation.

This way you can save money, cables and secondary equipment. Centralized control is carried out in the main control room, such as generators, main transformers, busbar sections and busbar contact circuit breakers and other important equipment, all adopt centralized control mode. In this control mode, there is usually a distance of tens to hundreds of meters between the controlled circuit breaker and the main control room, so it is also called "remote control".

The control of the circuit breaker is achieved through the auxiliary circuit. The control screen in the main control room should be equipped with control switches or buttons that can issue closing and opening commands, and the circuit breaker should have operating mechanisms to execute commands (i.e. closing and opening coils). The control switch and the operating mechanism are connected by a control cable.

The electrical circuit that completes the closing and opening tasks of the circuit breaker is called the control circuit. According to the type of operating power supply, the control circuit can be divided into DC operation and AC operation. According to the wiring and equipment used, there are strong current control and weak current control two categories.

1.Circuit breaker basic requirements

There are many types of circuit breakers and various operating mechanisms, so there are many types of control circuits. However, the basic requirements are the same.

(1) can be manually closed and opened, can also be realized by the relay protection and automatic device automatic closing and opening. After the closing and opening operation is completed, the closing and opening circuit should be automatically cut off to avoid burning out the coil.

(2) can indicate the circuit breaker closing, opening position state. When the circuit breaker is in the closing position, the red signal lights up; At the switch position, the green signal lights up. The flash indicates its automatic closing and switching state. The control circuit shall be protected by fuses.

(3) can monitor the integrity of the control circuit and power supply.

(4) with mechanical or electrical anti-jump locking device.

(5) Wiring should be simple and reliable.

2. Several control circuits of circuit breaker

(1) Manual and automatic control circuit. The figure shows the circuit for manual and automatic control of circuit breaker 1101 and switching. SA in the figure is the control switch with a self-replicating mechanism, that is, the handle will automatically return to the original middle position when the circuit breaker is finished.

QF2 and QE respectively represent the opening and closing coils of the electromagnetic operating mechanism; KM is the closing contactor; QF1 and QF4 are the auxiliary contacts of the circuit breaker QF; IKAU is the normally open contact of the rl operating device; KPo is the normally open contact of the protection outlet relay.