The Auto Reclosing Circuit Breaker is an automatic device that automatically switches the circuit breaker on demand. The operation experience of power system shows that most of the faults of overhead lines are transient, and the permanent faults are less than 10%. Therefore, after the short-circuit fault is removed by relay protection, the arc will be extinguished instantaneously, and the insulation at the short-circuit can be restored automatically in most cases. Therefore, the automatic overlap of circuit breakers not only improves the security of power supply, reduces the loss of power outage, but also improves the transient stability level of power system, and increases the transmission capacity of high-voltage lines. Therefore, overhead retransmission is necessary.

ONE. The function of automatic reclosing in power system

Overhead line faults are mostly "instantaneous" faults. After the line is disconnected by the quick action of relay protection control circuit breaker, the insulation level of the fault point can be restored by itself, and the faults disappear immediately. At this point, if the broken circuit breaker is reclosed, it will be able to resume normal power supply.  

In addition, there are "permanent faults", and after the circuit is disconnected, "permanent faults" still exist, even if the power supply is closed, can not restore normal power supply.

Therefore, the Auto Reclosing Circuit Breaker is adopted in the power system, that is, when the circuit breaker trips by relay protection or other non-manual operation, it can automatically control the reclosing of the circuit breaker.

TWO. The function of reclosing in power system

1. Greatly improve the reliability of power supply and reduce the number of power failures.
2. PV Auto Reclosing on high voltage transmission lines can improve the stability of power system parallel operation.
3. Reclosing the overhead lines can delay the erection of double circuit lines to save investment.
4. It can also rectify the wrong tripping of circuit breaker caused by bad mechanism or wrong action of relay protection.

However, when it coincides with permanent faults, PV Auto Reclosing will also bring some adverse effects, such as:

(1) The power system is once again subject to the impact of failure.
(2) Because the circuit breaker cuts off two short-circuit currents continuously in a very short time, its working conditions become worse.

THREE. Basic requirements for automatic recloser devices.

1. In normal operation, when the circuit breaker trips by relay protection or other reasons, the automatic reclosing device should operate.
2. PV Auto Reclosing should not start when the circuit breaker is disconnected by manual operation or remote control.
3. After the relay protection is removed, the automatic reclosing device should send out the reclosing pulse as soon as possible.
4. The number of actions of the automatic reclosing device should meet the requirements in advance.
5. The Auto Reclosing Circuit Breaker shall be capable of accelerating the action of relay protection before or after reclosing in order to accelerate the removal of faults.
6. When reclosing the two power supply lines, the reclosing should meet the closing conditions.
7. When the circuit breaker is in abnormal state and does not allow reclosing, the automatic reclosing device should be locked.