Analysis of the 6kV System Overvoltage Caused by the Input of the 35kV Vacuum Circuit Breaker

摘要

In this paper we analyze possible causes of the Very Fast Transient Overvoltage (VFTO for short), which can be found occasionally when an SVC is brought into service by a vacuum breaker. Using EMTP, a simulation model is built based on a practical and simplified application. Two possible causes are found accordingly. One is the resonance of the circuit oscillation and the VFTO in power cables, and correspondingly a rule of fault identification is given. The other is the undersize direct-to-ground capacity of the transformer's 6kVside, and a method is introduced to evaluate the effect when using another capacitor bank to limit the peak value of VFTO.