The Study On UHF Signal Propagation Characteristics And Sensor Arrangement Of GIL Partial Discharge

In recent years,with the rapid development of large-capacity and long-distance power transmission technology,gas-insulated metal-enclosed transmission lines(GIL)have been widely used in the power transmission field due to their strong applicability,excellent electromagnetic compatibility,reliable operation,and easy maintenance.The GIL filled with SF6 gas works in a slightly non-uniform electric field.Once the defect destroys the uniformity of the electric field,partial discharge will occur,and its insulation performance will be greatly reduced.In severe cases,it will cause insulation breakdown.Therefore,in order to ensure the safe operation of GIL equipment,it is necessary to discover its insulation hazards in time.Partial discharge is an important means of insulation detection.The UHF detection can realize the detection and positioning of partial discharge by detecting the UHF electromagnetic waves excited by the partial discharge inside the equipment.The UHF method has excellent anti-interference performance and high detection sensitivity,and is especially suitable for GIL equipment composed almost entirely of wave-guide structures.Firstly,this paper analyzes the common fault types,fault causes,partial discharge generation mechanism of GIL and the frequency characteristics of electromagnetic wave signals.Then gaussian pulse is used as the excitation source to study the propagation characteristics and influence coefficient of UHF electromagnetic signal in GIL coaxial wave-guide,insulator,l-shaped corner structure and t-shaped branch structure.By studying the attenuation of the electromagnetic wave signal through the straight cavity,insulator,L-shaped corner structure and T-shaped branch structure,the reference layout principle of the UHF built-in sensor in the actual project of GIL is summarized.At the same time,the propagation characteristics of the electromagnetic wave signal after escaping through the metal ring casting hole are studied,and the layout strategy for the external sensor is proposed.