The automatic reclosing circuit breaker is a facility that automatically recloses the circuit breaker by using a mechanical device or an automatic relay device after it is opened for some reason. If the fault in the power system is temporary, after the circuit breaker is tripped by the relay protection device to cut off the power supply, it will be automatically reclosed after a predetermined time. If the fault has been automatically eliminated, the line will resume power supply; if the fault is persistent, the circuit breaker is tripped again and is no longer reclosed. According to the number of reclosings, it is divided into one-time reclosing and multiple reclosing; according to the number of phases, it is divided into three-phase and single-phase automatic circuit reclosers; Generally speaking, the automatic circuit recloser is divided into four states: single-phase reclosing, comprehensive reclosing, three-phase reclosing, and deactivation reclosing.
Most lines of 110kV and above use three-phase one-time reclosing. According to operating experience, more than 70% of short- circuit faults on high-voltage overhead lines of large grounding current systems above 110kV are single-phase grounding short-circuits, especially for overhead lines above 220kV. The distance between the lines is large, and the single-phase ground fault is even as high as 90%. In this case, if only the faulted one phase is disconnected, and then single-phase reclosing is performed, and the two non-faulted phases are continued during the reclosing cycle, the reliability of the power supply and the system can be greatly improved. Parallel operation stability. Therefore, in the large ground current system above 220kV, single-phase reclosing is widely used.
Generally, single-circuit tie lines with voltages of 220kV and below, and lines with weak interconnection between power sources on both sides (including electromagnetic ring networks with weak connection through low-level voltage lines), especially high-voltage distribution lines of large-scale steam turbine generator sets.
When a single-phase ground fault occurs, the single-phase circuit recloser method is adopted, and when a phase-to-phase short circuit occurs, the three-phase reclosing method is adopted. Generally, when three-phase reclosing is allowed, but single-phase reclosing has a better effect on the system or power supply recovery, the comprehensive reclosing method can be used.
Three-phase reclosing means that when a single-phase short circuit or an inter-phase short circuit occurs on the transmission and distribution lines, the relay protection device will trip the three-phase circuit breaker of the line at the same time, and then start the automatic reclosing and then reclose the three-phase circuit breaker at the same time. way of the device. Generally, there are power supply and electricity users on both sides of the line, and the line with strong mutual connection adopts three-phase automatic circuit recloser.