Simulation on VFTO by Phase-Selection Technology in Low Voltage

Abstract

Disconnector(DS) operations in GIS may generate very fasttransient overvoltage (VFTO), which is characterized by its high peak value, short rise time, and high frequencies. However,most studies on VFTO are based on statistical data, which cannot show the impact of different phases to VFTO.In this paper, we use a relay with MCU as the Phase-Selection controllerto closeto the 220V power supplyin order to simulate VFTO in high-voltage substations, and acquired transientvoltage waveform of each phase. After analyzing the measured data, some important characteristics of switching fields were obtained. The lower the absolute value of the instantaneous power supply voltage is, the smaller VFTO is. When the absolute value of the instantaneous power supply is same, the amplitude of negative polarity VFTO is of about 20% smaller than the positive polarity in average, the lower the absolute value of the voltage is, the smaller the gap is. These characteristics are useful for theoretical analysis and practical engineering analysis inpower substation.If Phase-Selection controller can be used on disconnnector, then try to close at 0 degrees to left or 180 degreesto right, the offset phase is determined by controller's phase error.