Analysis of electromagnetic transients in secondary circuits due to disconnector switching in 400 kV air-insulated substation

•Transients due to disconnector switching in 400 kV air-insulated substation are presented.•Stray capacitance between HV and LV side of CVT is important above 10 kHz.•Transferred overvoltages increase as CVT secondary burden decreases.

This paper describes the electromagnetic transients caused by disconnector switching in 400 kV air-insulated substation. Transient overvoltages in the secondary circuits of capacitor voltage transformer (CVT) have been calculated using the EMTP-ATP software. The transfer of electromagnetic transients through substation's grounding grid has been analyzed in order to determine the overvoltages at the terminals of protective relays located in the control (relay) room. The overvoltages in secondary circuits have been recorded during on-site test.