Analysis of lightning transient voltage in large hydropower station based on ultra-wideband voltage monitoring

Abstract

When lightning strikes the outgoing lines of a hydropower station， it induces severe overvoltages. Then， the operation of gas-insulated switchgear （GIS） and circuit breakers within the station also triggers very fast transient overvoltages （VFTO）， posing a significant threat to the insulation safety of GIS and transformer equipment. To address this， an ultra-wideband transient voltage sensor is installed on the high-voltage side of the GIS equipment at the main transformer of the hydropower station. This establishes an online monitoring system for transient voltages， capturing the transient response process in the hydropower station during lightning strikes on its outgoing lines. Through the analysis of time domain and frequency domain characteristics of transient voltage， it is observed that when the outgoing lines of the hydropower station experience a lightning-induced ground fault， fracture reignition may occur in the circuit breaker. Based on the waveform of the lightning transient voltage infiltrating the hydropower station， accurate single-end fault location can be achieved. When the lightning strike on lines occurs within 10 km of the hydropower station， the transient voltage infiltrating the station poses a threat to transformer insulation. The ultra-wideband transient voltage monitoring system accurately records abnormal transient events within the hydropower station. Comparative analysis of the time domain and frequency domain characteristics of transient waveforms at various measurement points facilitates the localization of transient excitation sources. This aids in the early detection of equipment anomalies， providing timely warnings and ensuring the reliability of equipment operation and stable hydropower dispatch.

Keywords

• ultra-wideband voltage monitoring
• outgoing line of hydropower station
• lighting strike
• transient voltage
• time-frequency analysis