During on-site withstand voltage tests of gas-insulated switchgears (GIS)

once a breakdown occurs

it is hard to locate the breakdown position due to the intricate branch structures and minimal breakdown energy. The existing methods may require the placement of a large number of sensors with unsatisfactory accuracy

which adversely affects the process of inspecting and repairing

as well as the subsequent tests. To address this issue

this paper introduces a novel GIS breakdown location method. This method is predicated on the natural frequency of the transient voltage caused by the breakdown. The relationship between the breakdown position and the natural frequency is first derived

which is referred to as the location equation. Then

the natural frequency characteristics are discussed from both mathematical and energy perspectives. Based on these characteristics

the location method is proposed that utilises the location equation and the frequencies at two measurement points. The results of the laboratory experiments demonstrate the accuracy of the method and certain advantages over the ultrasonic method. Further

the effectiveness of the method in GIS and gas-insulated transmission lines (GIL) with complex structures and high voltage levels is also confirmed by simulation cases and field experimental data.