Influence of key structure parameters on electrical field distribution of tri-post insulator used in UHV

Gas insulated metal enclosed line (GIL) has been widely applied in power transmission system due to its high safety and reliability level. Because of its cost saving production and excellent mechanical property, tri-post insulator is the key structure of insulation in GIL. Therefore, the safe operation of tri-post insulator determines the insulation strength level of GIL. Tri-post insulators have the characteristic structure with post zone and sphere zone. The thickness and width of sphere zone, conical degree and radius of post zone, depth and radius of metal insert have great influence on electrical field strength. High electrical field are mainly distributed on surfaces of insulator and metal inserts. Over-high partial electrical field may cause the partial discharge or insulation failure. This paper has researched how these parameters impact the field strength, and adjusted the parameters listed above to lower the maximum field value, which is vital for insulation structure design and production.