Abstract
This paper describes overvoltage caused by disconnecting a lot of motor-loads on a power distribution line with power-factor-correcting capacitors during a transmission line open-phase. The overvoltage phenomena are studied by a field test, a steady-state analysis and a transient analysis. Experimental results show that the line-to-line voltage on a 6.6kV distribution line with an open-phase 22kV transmission line amounts to 1.7 per unit. The overvoltages are caused by two types of resonance. One is the linear circuit resonance between the power-factor-correcting capacitors and the secondary side impedance of motors. The difference between positive components and negative ones of the impedance produces the resonance. The other is the non linear circuit resonance between the power-factor-correcting capacitors and the saturated reactances of a transformer.
