Study On The Propagation Characteristics Of UHF Partial Discharge Electromagnetic Wave Signals In GIL

Gas-insulated metal enclosed transmission line(GIL)has been widely used in modern power system thanks to its extensive applicability,strong electromagnetic compatibility,more maintainable and reliable in operation.As a result of modular design on GIL system,it has sophisticated manufacturing and overhaul processes,which makes it difficult to apply some conventional monitoring method.Therefore,the ramifications will be severe onece partial discharges fault occurred.In order to recover the equipmemnt quickly when things go wrong,monitoring system are usually installed in GIL.UHF method has strong anti-jamming capability and high detection sensitivity,particularly applies to GIL equipment which is nearly composed of coaxial transmission wave-guides.Online monitoring and roughly location of fault points can be achieved by detecting UHF signal through UHF sensors.For an in-depth understanding of the propagation characteristics of UHF electromagnetic signals in the GIL,thereby achieving economical and reasonable placement of UHF sensors.Based on the GIL testing line product by NARI group,this paper study the propagation characteristics of UHF signals in GIL.First,some typical structures of GIL like cavity,insulators,L-type branch,T-type branch and segregation unit are buit by Pro/E,then import these files into electromagnetic simulation software XFDTD to analyze the time-frequency property of UHF signals in varied structures of GIL,electric field distribution of GIL cross cection and distribution of high-order mode.By investigating the influence of GIL special structures on propagation characteristics,summing up the placement law of UHF built-in sensors in practical GIL engineering.Furthermore,the signal characteristics have been studied when UHF electromagnetic wave pass through disc spacer and propagate via hole of GIL mental flange,based on this the placement law of external radiating antenna has been proposed.