Electric field calculations by boundary element method for a 230 kV composite bushing

Composite polymer bushings provide technical and safety advantages over other types of bushings. The US Navy is making an attempt to use composite bushings of two different diameters (24" and 30") in their applications. The composite bushings are made of a fiberglass tube surrounded by silicone rubber sheds as housing. The high voltage cylindrical conductor runs through the centre of the bushing. There are aluminum flanges at the two ends. The bushings are filled with gases like SF₆ at a certain pressure. A study of potential and electric field is an important index in determining the limits of corona free operation. Corona is detrimental to polymer materials. Potential and electric field calculations for a 230 kV composite bushing are presented. An electric field solver package, COULOMB^©, has been used for the analysis. The role of field shaping elements in relieving electric stress is discussed.