Research On Applications Of Ultrasonic Partial Discharge Detection Method In GIS Equipment Breakdown Test

GIS is short form of gas insulated switchgear, which combines the primary equipment into one unit. GIS equipment has advantages of long maintenance cycles, safe and reliable operation and few maintenance workloads, etc., which makes GIS equipment widely used in power system, and its safety and reliability has also been widespread concern all over the world.The insulation fault is always one of the important factors affecting the reliability of GIS; the withstand voltage test can detect the insulation status of GIS, ultrasonic wave generated in the discharge process is an important method in discharge process. The partial discharge characteristics and classic fault model in GIS is studied. A multi-channel GIS fault detect system is developed, with which GIS breakdown location method and insulation fault analysis is studied.The applications of ultrasonic test method in GIS withstand voltage test is studied, which mainly includes:The source, develop process of partial discharge in GIS are studied. Based on three capacitors model, the equivalent circuit, frequency characteristics and discharge current, and real discharge magnitude are studied.5 classical independent insulation failure models in GIS are designed, which are needle-plate model, leakage model, floating potential model, inner gap model and free metal particle model. Based on FEM method, the space electric field strength distribution of these models are calculated with the software ANSYS.Ultrasonic partial discharge detecting method is studied. The mechanism of ultrasonic wave generated by partial discharge is analyzed from the physics aspect, which include the frequency spectrum and the propagation characteristics; the detection principle, detection process and classic discharge spectrum of partial discharge are studied; the time-frequency characteristics of the 5 classic insulation failures are studied.A multi-channel ultrasonic GIS failure detection system is developed based on wireless network and digital signal process method, the data sampling and transmission model of the hardware is developed. Fault measurement software is programmed with Microsoft Visual Studio.Net 2008.GIS breakdown location method based on multichannel acoustic emission principle is introduced. The breakdown in 550kV GIS withstand voltage test of a 500kV substation is detected with the ultrasonic partial discharge detecting system. The fault reason is analyzed according to the returning factory check and free particle material analysis in the fault air chamber.