Disconnector or breaker switching operations generates Very Fast Transient Overvoltages (VFTO) in Gas Insulated Substations (GIS). These VFTO have their rise-times in the range of a few nanoseconds and is followed by high frequency oscillations which can endanger the insulation of transformer winding. Hence it is necessary to develop appropriate models to study these transients. In this study, a simplified transformer circuit model capable of simulating the high frequency range from 100 kHz to several MHz is proposed to simulate the high frequency surge over voltages generated in an actual system. A 22 kV interleaved transformer winding is considered for the analysis. Resonant frequencies for different transformer models are obtained in circuit simulation package and compared with measured frequencies obtained from Sweep Frequency Response Analyser (SFRA). The results of the proposed model demonstrate better agreement with the measured values.
展开▼
