Damaging Open-Phase Overvoltage Disturbance on a Shunt-Compensated 500-kV Line Initiated by Unintended Trip

Abstract

Shunt reactors are applied to long extra high voltage transmission lines to compensate for their natural capacitance which otherwise could cause over-voltages under light load conditions. However, when the level of compensation approaches around 65% or higher, these reactors themselves can, due to contingency, become the cause of hazardous over-voltages during unbalanced openphase conditions on the healthy line. This paper reports on an over-voltage incident that occurred on a 500 kV 72% shunt compensated line in the BC Hydro System. The overvoltage occurred when one of the breaker poles failed to interrupt the current following an inadvertent three-phase trip of the healthy line. The uninterrupted current kept one phase energized for an extended time. Temporary overvoltages during this condition and restrike transients eventually led to surge arrester failures at both terminals.Analysis of recordings of voltage and current provided useful insight into the mechanism responsible for the damaging over-voltages as well as the protection and control responses during the disturbance. The intent of this paper is to share the knowledge gained from analyses of the recorded waveforms with other utilities either having or planning for highly compensated lines.

The resonance overvoltages in nonsinusoidal modes of extra high voltage transmission lines

“…Non-sinusoidal modes are characterized by the appearance of higher harmonics of current and voltage [4,6,[9][10][11]. The distortions of voltage and current waveforms in the case of non-sinusoidal modes appear due to nonlinearity of the magnetization shunts of unloaded autotransformer.…”

“…Because of the reasons mentioned above, the simulation model has been developed in environment MATLAB ® / Simulink ® [1,9] Fig. 1.…”

Integrated Photovoltaic Inverters Based on Unified Power Quality Conditioner with Voltage Compensation for Submarine Distribution System

“…In normal or heavy load conditions, undervoltage will occur due to cable resistance or cable inductance. On the other hand, in light loads, overvoltage can occur due to submarine cable capacitance-the so-called Ferranti effect [6,7]. In this condition, sensitive electric equipment can be damaged due to undervoltage or overvoltage grid conditions.…”

Effect of interphase magnetic coupling of shunt reactor on transmission‐line open‐phase overvoltages and neutral reactor optimisation

“…Nagpal et al [3] reports occurrence of damaging overvoltages of about 1.7 pu on two open‐phases of a 500 kV 72% shunt compensated TL when the other phase remained energised due to stuck breaker pole. The observed overvoltages are analysed based on electromagnetic transient simulations, and some mitigation methods are proposed to avert similar events in the future.…”