송전계통에서의 보호계전 방식을 고려한 순간전압강하 평가 연구

Abstract

This paper presents how to evaluate the expected sag frequency at sensitive load points considering the protection schemes in transmission systems. Voltage sag is one of the most severe problem of power quality. Voltage sag is defined as short duration reduction of RMS voltage, and mainly caused by faults in power system. Industrial process involving sensitive equipment can be affected by such voltage sags. Voltage magnitude and duration are essential characteristics of a voltage sag. The magnitude mainly depends on the fault location and fault type. The voltage sag duration depends on the flow duration of the fault current in a network. Therefore, the duration can be determined by the characteristics of the system protection. In order to establish the optimal countermeasures against voltage sags, the voltage sag assessment at sensitive load points should be performed. In general, the magnitude is only considered in the assessment of voltage sags. However some equipment can be affected by duration as well as magnitude of voltage sag. In this paper, a method for assessing voltage sag durations considering the characteristics of the protection systems is addressed. The proposed method can be efficiently used to assess the voltage sag performance of a transmission system.