A Non-Intrusive Electrical Discharge Localization Method for Gas Insulated Line Based on Phase-Sensitive OTDR and Michelson Interferometer

To overcome the high cost and low-spatial resolution of the electrical discharge localization systems for the gas insulated line (GIL), a non-intrusive distributed optical fiber sensing system based on the phase-sensitive optical time domain reflectometer (phi-OTDR) and the optical fiber Michelson interference is proposed. In the system, the Michelson interference provides a trigger signal since it has a better sensitivity and a higher frequency response, and the phi-OTDR localizes the ultrasonic vibration induced by a discharge. First, the principle of the proposed discharge localization system is introduced. Then, the bandwidth and multi-points distributed sensing performances of the system are investigated based on the ultrasonic signal induced by a piezoelectric transducer. Furthermore, the localization results of experiment using gas insulated switchgear spacer discharges indicate that the sensing distance of the sensing system can reach 1 km and the positioning accuracy of the discharge is smaller than 15 m. Thus, the system meets the requirement of the GIL discharge localization. Contrary to the traditional GIL discharge methods, the system has several advantages, such as non-intrusive, better spatial resolution, lower cost, and greatly simplified structure.