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Basic Requirements for Automatic Circuit Recloser

Ⅰ. The number of actions of the automatic circuit recloser


The number of actions of the automatic circuit recloser should meet the pre-determined. For example, a three-phase reclosing device should only act once. When the reclosing device trips again after a permanent fault, it should not run again. In any case, such as damage to the components of the device itself, sticking of the relay contacts or refusal to move, the reclosing should not cause the circuit breaker to repeatedly reclose to a permanent fault.


Ⅱ. The reset method of the automatic circuit recloser


After the reclosing device is activated, it should be able to automatically reset and be ready for the next action. However, for lines with voltages of 10kV and below, if there are local personnel on duty, manual resetting can also be used to simplify reclosing. The disadvantage of using manual reset is that after the reclosing action, the automatic circuit recloser will refuse to act before the on-duty personnel does not reset in time, and another failure occurs. This is especially likely to happen in the thunderstorm season, where there are more lightning activities.


Ⅲ. Action time of automatic circuit recloser


The action time of reclosing is generally 0.5~1.5s. The reclosure time should be as short as possible to shorten the power outage time. Because the speed of the motor drops sharply after the power supply is interrupted, when the reclose is successful, the motor should start automatically. The lower the speed, the greater the self-starting current and the longer the time. This often causes the grid voltage to drop too much, making self-starting more difficult and delaying recovery. Normal working time. However, the reclosing time should not be too short. The time should be longer than the time for the insulating medium to dissociate, so that the insulation strength of the fault point can be restored in time, and the operating mechanism of the circuit breaker should be restored in time to be able to reclose, such as an oil circuit breaker. To make the insulation strength around the contacts have time to recover, the arc extinguishing chamber has time to be filled with oil.


Ⅳ. Coordination of automatic circuit recloser and relay protection


There should be a circuit that accelerates the protection action before or after reclosing, so as to better cooperate with the protection device and accelerate the removal of the fault. The pre-acceleration protection of the automatic circuit recloser is referred to as pre-acceleration, that is, when a fault occurs on the line, the fault is removed by the instantaneous action of the protection for the first time, and then the reclose is performed. If the reclose is on a permanent fault, there are options according to the protection configuration Jumped away. The front acceleration protection is mainly used in the direct wiring route from power plants or important substations below 35kV to quickly remove faults and ensure the bus voltage.


The post-acceleration protection of the automatic circuit recloser is called post-acceleration for short. When the line fails for the first time, the protection has a selective action and then recloses. If the reclose is on a permanent fault, the protection action is accelerated after the circuit breaker is closed. Instantaneous removal of the fault. Post-acceleration protection is mainly used in networks above 35kV and transmission lines that supply power to important loads. If the automatic circuit recloser acceleration mode is adopted, the inrush current generated at the moment of closing and the zero sequence and negative sequence current generated by the three-phase contacts of the circuit breaker not closing at the same time may cause the protection to malfunction, and measures should be taken to prevent it.


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