Auto reclosing circuit breaker is widely used in overhead line transmission and overhead line power supply lines on the effective anti-accident measures (cable transmission, power supply can not be used).
That is, when the line fails, after the circuit breaker is tripped by relay protection, the auto reclosing circuit breaker closes the circuit breaker again after a short time interval. In most cases, line faults (such as lightning stroke, wind damage, etc.) are temporary. The insulation performance (insulator and air gap) of line can be restored after circuit breaker tripping, and the reclosure can be successful, which improves the reliability of power supply in power system.
The minimum allowable time interval for reclosure is 0.15-0.5 seconds. The higher the rated voltage of the line, the longer the deionization time of insulation. The success rate of automatic reclosure depends on the line structure, voltage level, meteorological conditions and main fault types.
According to the statistics of Chinese electric power sector, it can generally reach 60%-90%. Another widely used anti-accident measure in power sector is the automatic input of standby power supply, which usually takes 0.2-0.5 seconds. It requires little investment and brings great economic benefits to maintain normal power supply.
Main functions of auto reclosing circuit breaker:
1. It greatly improves the reliability of power supply and reduces the number of power outages, especially for single-circuit lines with one-side power supply.
2. Using Reclosure on high voltage transmission lines can also improve the stability of parallel operation of power system.
3. In the process of design and construction of power grid, in some cases, the double-circuit line can be postponed to save investment due to the consideration of reclosure.
4. It can also correct the wrong tripping of circuit breaker itself caused by bad mechanism or misoperation of relay protection.
The economic benefit of reclosure should be measured by the national economic loss caused by power outage when there is no reclosure. Because the reclosing device itself has low investment and reliable operation, it has been widely used in power system.
