Measurement of Overvoltage Induced by Breaker Operation in a Pumped Storage Power Plant

In recent years, several cable and transformer failures have occurred in pumped storage power plants (PSPPs). Because the structures in the PSPPs are different from the traditional power substations. We suspected that overvoltages induced by breaker operation are causes of the failures. However, the PSPPs are usually located in remote mountainous areas where testing opportunities are rare. The switching transient research has been rarely reported. So the field measurement results arevery important for studying the failure factors. In this paper, through the previous very fast transient overvoltages (VFTO) sensors, the field switching transient waveforms were measured in a 500 kV PSPP. According to the measured waveforms, the measured wave velocity in the high voltage cable was 151.2 m/μs. The maximum amplitude of switching overvoltage induced by breaker operation was 1.04 p.u. (per unit). Meanwhile, more than 5 times oscillation and polarity reversal could be a great threat to the transformers and cables, which may weaken the insulation and cause serious damage.