what is automatic reclosing switch?
Introductoin of automatic recloser
The automatic reclosing switch circuit breaker is automatically reclosed by mechanical means or relay automatic device after it has been tripped for some kind of fault. If the fault occurred in the power system is temporary, after the circuit breaker trips to cut off the power supply by the relay protection device, it will automatically reclose after a predetermined time. If the fault has been automatically eliminated by itself, the will resume power supply; if the fault is continuous Then, the circuit breaker is tripped again and no longer reclose. According to the number of reclosing, there are one-time auto recloser and multiple-time recloser; according to the number of phases, there are three-phase and single-phase automatic recloser; according to the application circumstances, there are single-side power supply recloser and double-side power supply automatic recloser.
In the failure of power systems, most of them are faults of transmission lines (especially overhead lines). Operational experience has shown that overhead line faults are mostly “transient”, for example, flashover caused by lightning, flashing caused by strong winds, short circuits caused by birds and branches falling on the wires, etc. After being quickly disconnected by the relay protection, the arc is extinguished, and external objects (such as branches, birds, etc.) are also burned by the arc and disappear. At this time, if the disconnected circuit breaker is closed again, normal power supply can be restored. Therefore, such a fault is called a “transient fault.” In addition to this, there are also “permanent failures” such as failures due to line reversal, wire breakage, insulator breakdown or damage, and they are still present after the line is disconnected. At this time, even if the power is turned on, since the fault still exists, the line is again disconnected by the relay protection, and thus the normal power supply cannot be restored.
Since the fault on the transmission line has the above properties, it is possible to greatly improve the reliability of the power supply by performing a closing after the line is disconnected. For this reason, an automatic reclosing device capable of automatically closing the circuit breaker after the circuit breaker trips is widely used in the power system.
The automatic reclosing device is an automatic device that automatically inputs the circuit breaker as needed after the fault has been removed. The experience of power system operation shows that the vast majority of faults in overhead lines are “instantaneous”, and permanent faults are generally less than 10%. Therefore, after the short-circuit fault is removed by the relay protection action, the arc will automatically extinguish, and in most cases the insulation at the short-circuit can be automatically restored. Therefore, automatically overlapping the circuit breakers not only improves the safety and reliability of the power supply, but also reduces the power loss, and also increases the transient level of the power system, increases the power transmission capacity of the high voltage line, and corrects the miss-trip due to Mal-operation caused by the relay or relay protection device. Therefore, automatic reclosing is required for overhead lines.
The main role of automatic reclosing:
(1) greatly improve the reliability of power supply, reduce the number of power outages, especially the single-circuit line of single-sided power supply;
(2) The use of reclosing on the high-voltage transmission line can also improve the stability of the parallel operation of the power system;
(3) In the process of designing and constructing the power grid, in some cases, due to the role of reclosing, it is possible to suspend the double-circuit line to save investment;
(4) It can also correct the malfunction of the circuit breaker itself due to malfunction of the mechanism or malfunction of the relay protection.
For the economic benefit of reclosing, it should be measured by the loss of national economy caused by power outage when there is no reclosing. Since the reclosing device itself has a low investment and is reliable in operation, it has been widely used in power systems.