Design of UHV Long-distance GIL Fault Location System Based on Ultrasonic Method

The length of the single-phase line of the Sutong GIL tunnel is about 6km, and the length of a single gas chamber is about 100m. Because the GIL adopts a fully sealed design, it is difficult for the existing methods to accurately locate the fault when discharge and overheat faults occur during operation. In order to meet the long-distance fault location requirement of Sutong GIL, this paper analyzed the breakdown, propagation and attenuation characteristics of ultrasonic signals in GIL through test. The test results show that the frequency of the ultrasonic signal generated by breakdown should be distributed in the frequency of 40$\sim$60kHz, 100$\sim$150kHz, 230$\sim$250kHz and 500$\sim$530kHz. In addition, the attenuation of ultrasonic signal is 70% and 89% after passing through the gas chamber basin and expansion joint. Based on the above research results, this paper designed the configuration and parameters of the sensors, communication scheme and protection scheme of the long-distance GIL ultrasonic fault location system in detail, and verified the fault location function of the system through engineering app-cations.