In case of insulation breakdown accident of ultra-high voltage（UHV） gas insulated metal-enclosed transmission line（GIL）

the accurate location of breakdown position is conducive to emergency repair and rapid recovery of power transmission. This paper proposes a fault location method based on transient voltage monitoring for UHV GIL

which is actually applied in 1 100 kV Sutong GIL utility tunnel project. The system includes voltage sensor

monitoring terminal

and storage and control unit

which are successfully installed and implemented. During GIL field tests

when the GIL flashover occurs

the system successfully triggers and completely records the transient voltages generated during the breakdown. Through waveform analysis

it is found that when UHV GIL solid insulation breaks down

the half-wave steepening time of transient voltage is less than 130 ns and spreads between the breakdown point and bushing port

forming a typical traveling wave process. According to the time when the transient traveling wave first reaches the measuring points at both ends of GIL

combined with the propagation speed of traveling wave

the accurate position of the fault point is calculated and the fault point is quickly disassembled for maintenance. According to the results of disintegration verification

the positioning error of the system is less than 5 meters. It can be seen that the adoption of wide-band voltage sensing based on capacitive voltage divider can realize the rapid and accurate location of insulation breakdown faults of UHV GIL

which is conducive to improving the operation reliability of UHV transmission system.