UHF Partial Discharge Detection Technology For GIS Based On Envelope Detection Circuit

Nowadays,GIS(Gas Insulated Substation)is the most important part of the insulation safety of substations.Partial Discharge(PD)detection can effectively detect insulation faults.It has the remarkable advantage of avoiding all kinds of interferences in the field by using UHF method to detect partial discharge in GIS.So it is widely recognized in power grid enterprises.Now the ultra-high frequency partial discharge monitoring system is favored by the grid operation and inspection units,because the system can monitor the operation of GIS all-weather,in order to ensure the reliable grid operation which is of great significance.UHF method has many advantages,but the field partial discharge defects have various types,and it may occur in various locations.Thus the test signal has certain differences.Whether these differences can be accurately identified and the fault types can be accurately judged,there are still difficulties in engineering application.A real-type test system of GIS is established based on operation state.The size,internal structure and equipment arrangement of the sealed are same with the actual situation.The non-PD high voltage system is changed from the traditional single-phase to the three-phase system,which is more suitable for the actual operation state.And it can be connected with the power grid to simulate the operation state of GIS as far as possible.The ultra-high frequency sensor is optimized and designed.The UHF signal has been intelligent analysised sampled and fast processed by combining high-speed oscilloscope and computer.Five typical discharge models are optimized.In the models,the distribution of field intensity,discharge intensity and discharge process around the discharge point are very similar to the actual PD in GIS.The whole propagation process of PD can be simulated more authentically and intuitively.Five kinds of typical discharge signals were collected from the test system of GIS.Feature extractions of single power frequency cycle UHF signal were completed in the traditional uncoated detection circuit.It was concluded that the characteristic recognition of discharge signals was too similar to be distinguished.By using the optimized detection circuit studied in this paper,the UHF signal is detected under stable partial discharge state.Thus,the same type of discharge detection signal has high similarity,while the different types of discharge envelope signals have obvious differences,which can be well compared and classified,so as to facilitate the identification of PD types.In order to verify and confirm the research results,lots of on-line monitoring datas of UHF PD are processed with the detection technique in this paper.Several suspected GIS discharge devices were detected and analyzed,and good results were obtained.