Research On Discharge And Flashover Characteristics Of Silicone Rubber Pillar Creeping Model Under DC Electric Fields

The solid-state insulation device and the charged conductors it is fixed are mostly in the air,and a discharge phenomenon occurs under the specific conditions at the interface between the insulation structure and the air,which is called creeping discharge.If the discharge develops into a penetrating air breakdown,it is called flashover.At present,silicone rubber is widely used as a high-voltage insulating material with excellent performance and is widely used in DC transmission lines and equipment insulation systems.In the actual operation of UHV DC equipment,different insulation structures require differences in the vertical component of the electric field on the surface of the insulating material.The surface flashover and discharge characteristics under different vertical components of the electric field are not the same,which will affect the withstand voltage evaluation and discharge detection system of the insulation structure.Therefore,the surface flashover and discharge characteristics under the vertical component of DC strength are urgently needed.Aiming at the above problems,a DC flashover and discharge experiments platform with the "pillar-plate-ring" three-electrode structure as the research subject was designed and constructed.Based on the test platform,by adjusting the diameter of the ring electrode and the bottom plate electrode,the adjustment of the creeping discharge pitch and the vertical component of the electric field of the silicone rubber is realized,and the electric field distribution of the material required for the test is obtained.Furthermore,the surface flashover voltage,the surface discharge PRPD spectrum and the creeping discharge waveform of the silicone rubber under various test conditions were measured and analyzed.The main research results are as follows:(1)The effects of vertical component of different discharge spacing,positive and negative polarity and electric field strength on flashover voltage are studied.The results show that under the same discharge spacing,the positive vertical strong vertical flashover voltage<positive weak vertical vertical flashover voltage<negative negative weak vertical flashover voltage<negative polarity strong vertical flashover voltage;with the increase of discharge spacing.The flashover voltage increases;but at short discharge intervals(1-2 cm)weak vertical component,the positive and negative flashover voltage values are similar.The analysis shows that the vertical component of the electric field is weakened under the condition of positive polarity.The characteristic flashover voltage a and the zero-probability flashover voltage y increase,and the sensitivity of the silicon rubber creeping insulation system to the voltage increment ?decreases;under the negative polarity condition,as the vertical component decreases,a,p,y decrease.As the discharge spacing increases,the difference between y and a increases.(2)The development law of creeping discharge of silicone rubber under the vertical component of positive and negative DC electric field is studied.The results show that the average discharge Qav and the discharge frequency Thc increase with the increase of the applied voltage amplitude and the pressurization time,and the Qav and Tnc of the strong vertical plane are larger and the strong vertical creeping discharge TRPD spectrum The graph shows discharge stratification at+14 kV and-16 kV.The results show that there are four types of discharge in positive and negative strong vertical creeping discharges:corona discharge,branch discharge,Single-channel discharge and multi-channel discharge;with the increase of pressurization time and voltage amplitude,the discharge type will be transformed into each other.The main discharge type is changed from corona discharge to branch discharge to single-channel discharge;in addition to corona discharge,discharge The rising edge time of the pulse decreases with the increase of voltage and approaches saturation,and the amplitude of the discharge pulse increases with the increase of voltage.The main types of discharge in the weak vertical plane are:corona discharge and single-channel discharge,but when the applied voltage is high,the surface component and air component appear in the discharge,and the phenomenon persists until flashover;compared with the strong vertical plane,the weak vertical The halo voltage is higher,the amplitude of the discharge pulse is smaller,the number of discharges is less,and the discharge is more random.