Abstract
An automatic fault-recorder installed in a substation of Chubu Electric Power Company detected a peculiar phenomenon that bus-bar voltage fell to around 20-30% of the nominal value for a short time (about 8-10 cycles) though electric current didn't change during the period. The phenominon was recorded several times.
In this paper, we analyzed the origin of this phenomenon and conducted simulations by EMTP. As a result, we estimated that this phenomenon occurred by the saturation of VT (voltage transformer), and this saturation caused by lightning strokes to the transmission line with line arresters, which have been increasingly installed in recent years. Moreover, we evaluated the influence of the phenomenon to protection relays.
