Research On The DC Discharge Performance Of Air Gaps With The Presence Of The Sand Particles

In HVDC projects,long distance transmission line and complex terrain of cross-domain make it necessary to consider the impact of regional climate characteristics.Frequent sandstorms in northwest China might have bad influence on external insulation characteristics of transmission lines and electrical equipment,threatening the safe and stable operation of power system.To study the discharge performance of typical air gap under sand conditions and fully grasping the insulation strength characteristics of air gaps could determine the required gap distance economiclly and reasonably in pratice,which has importance influence on HVDC projects in China.This paper researches on the sand characteristics of northwest region and gets the parameters of sand weather in northwest area such as wind speed,sand concentration and sand granularity.According to these parameters,A bar-board model is taken as an example and the simulation model of air gap electric field distribution based on the finite element method of electrostatic field is established.The software of COMSOL Multiphisics is used to calculate and analyse the electric field distribution of the bar-board air gap model under sand environment.With the sand weather simulation system and the meteorological parameters surveyed,a sand environment similar to that of northwest area is established.It takes the bar-bar and bar-board air gap as the research objects and carries out the test of typical gap discharge characteristic under sand condition.The discharge performance of air gaps under different conditions like wind speed,sand concentration and sand particles has been experimently studied.According to the electric field simulation results,the electric field distortion only appears around the area of several times the radius of sand when sand in air gap.The electric field distortion caused by sand with charge increases slightly but the electric field of air gap changes little due to the small size of sand particles.Wind speed,the size of sand particles and the concentration of sand have no obvious influence on DC Discharge voltage of Air Gaps.The relationship between air gap discharege voltage and gap distance is linear.Different sand conditions have no obvious influence on the character of gap DC discharge.