| With the development of the power grid,GIS（gas insulated switchgear）has become the key equipment in the modern power grid by its small volume and long maintenance cycle.It is inevitable that there will be insulation defects in GIS.Insulation defects are formed in production,installation and operation.The metallic protrusion defect on the surface of the GIS conductor is one of the insulation defects.The dielectric strength of SF6in GIS is significantly affected by the uniformity of electric field,the existence of metallic protrusion defect causes the existence of non-uniform electric field in the GIS,which seriously affect the dielectric strength of GIS.In addition,due to poor seal or damp,the excessive H2O and O2content in GIS will also damage the dielectric strength of the equipment.The influence of metallic protrusion shape and excessive H2O and O2on streamer discharge process in GIS has been seldom studied in the past.In addition,it is difficult to react with the microscopic characteristics of discharge by experimental methods.This paper analyzes the influence of metallic protrusion shape and micro-water and micro-oxygen environment on insulation performance of GIS.This paper has some guiding significance for the operation safety assessment,manufacturing process improvement and operation maintenance of GIS.When the discharge process is in atmospheric pressure,long gap and under heterogeneous electric field,streamer discharge theory can better explain the micro discharge phenomenon.The fluid dynamics-chemical reaction mixing model is widely used in gas discharge research field.Based on the theory of streamer discharge,this paper adopts the fluid dynamics-chemical reaction mixing model.The macroscopic factors such as electrode structure and gas composition were changed.Introduce the changes of the electric field intensity,the average energy of the electron,electron density,streamer discharge channel and the average development rate of the discharge.The characteristics of streamer discharge are analyzed from the micro level.The main results of this paper are as follows:⑴Based on the streamer discharge theory,this paper adopts the fluid dynamics-chemical reaction mixing model,which is a commonly used model in gas discharge theory.The electron and ion drift-diffusion equations are established to describe the motion of charged particles.Poisson equation is established to calculate the electric field distribution.Verify the correctness of the model used.The longer the metallic protrusion is,the more harmful it is to the insulation performance of the equipment⑵A simulation model was built to simulate the appearance of metallic protrusion defect in GIS.By changing the shape parameters such as the head shape,length and radius of the metallic protrusion,analysis the damage of various metallic protrusion with different shapes due to different forming reasons to the insulation performance of GIS.The head shape and radius of the metallic protrusion are the most important factors to determine its influence on the insulation performance of GIS.The metallic protrusion with high curvature head shape and small radius is easy to have discharge accident,and eventually developed into gap breakdown.The longer the metallic protrusion is,the more harmful it is to the insulation performance of the equipment.Increasing the distance from the conductive rod to the housing in GIS is helpful to reduce the influence of metallic protrusion on the insulation performance of the equipment.⑶Aiming at the problem of excessive H2O and O2content in GIS,improvement the original SF6discharge chemical reaction model,considering the influence of H2O and O2on discharge reaction.Setting H2O and O2with different contents,research the influence of sealing failure and moisture exposure on insulation performance of GIS.Excessive H2O and O2will aggravate the risk of discharge accident in GIS.The more serious the excess of H2O and O2,the greater the probability of gap breakdown happen in GIS.Excessive H2O and O2will reduce the internal gas insulation strength of the GIS and damage the self-recovery performance of SF6. |
