Research And Development Of Power System Circuit Breakers Interdiction Capacity Of Real-time Calibration Function

Short-circuit currents in power systems are increasing with the economy increasing year by year. It is an insecure factor for power system operation if short circuit currents exceed breakers interrupting capabilities.Generally, there are four measures to limit short-circuit current: considering from designing power systems, changing the network topology, adding or changing equipments, add Fault Current Limiter (FCL) into power systems. Except the first and the third measures, Considering that no fundamental breakthrough has happened on existing fault current limiters yet, to change the network topology is the unique attainable way to limit short-circuit currents. It is necessary to check the interrupting capabilities of circuit breaker in real time because the network varies.To calculate short-circuit currents in a large system using a real-time short-circuit current analysis totally based on EMS system is first introduced in this paper.Then, the principles to get maximum short-circuit through breakers for typical breaker configurations based on the result of real-time short-circuit current calculation are analyzed in detail.In this paper, characteristic and structure of the Real-time Short Circuit Monitoring System (SCMS), developed with Zhejiang Electric Powrer Company cooperatively, were introduced in detail. Meanwhile, combining the actual running situation of the power network of Zhejiang province, the validity of various projects restricting the short-circuit current was analyzed by this system.The ANSI and IEC methods and standards of rating breaker-interrupting capabilities are explained. Some advice to choose breakers correctly is also put forward in the end of this paper.