The Research Of Capacitive Inrush Current Of High Voltage Circuit Breaker

Actual operating experience has shown that the accident rate of high-voltage capacitor banks has increased in recent years. More than half of the accidents are associated with the process of closing. Lots of papers indicate that the actual value of the capacitive inrush current is larger than the setting value of protection relay, causing the malfunction of circuit breakers, as a result of triggering the protection relay ahead of time, which could cause accdents. In order to investigate the reason of switching accidents of capacitive banks, the paper analyses the transient process of capacitive inrush current and its impact on high-voltage circuit breakers with the electromagnetic transient simulation software ATP-EMTP. Finally the paper sums up possible causes and the main work is as follows:on the one hand the paper analyzes how the inrush current varies and why the actual value of the capacitive inrush current is larger than the theoretical value. All the content can be summarized as the following three aspects:Firstly, the paper analyzes the transient process of capacitive inrush current under the condition of homochronous closing of three phases and under the condition of the actual closing process. Finally the paper gets the conclusion that the difference of closing time influences the transent process of the inrush current a lot, making the transient process very complex; Secondly, the paper recalculates the inrush current of back-to-back capicitor, and found that the capacitive inrush current calculating method of previous national standard ignores the influence of power source; Finally the paper analyzes how the actual coupling inductance influences the transient process of the capacitive inrush current, with ATP-EMTP program. Finally the paper got a conclusion that coupling inductance can make the inrush current much larger than the theoretical value.On the other hand, from the perspective of actual operations, this article analyzes how the inrush current influences the high voltage circuit breakers from the point of arc quenching principle and the structure of interrupters, production technology and so on. Finally the article proves the theoretical analysis with test report and gets the conculsion that the design of SF6 circuit breaker is more suitable for switching capacitor banks.