Minimisation of electric field stress at triple junction of a functionally graded cone type spacer in a gas insulated busduct with metal inserts

Abstract

Insulation integrity of supporting insulator plays a vital role for determining the continuity of service of the gas insulated substation which depends upon the electric field stress distribution on the surface of the spacer. Triple junction formed by the conductor, SF6 gas and support insulator is another critical area where the field stress is to be maintained at minimum value. Shape control is a technique employed for obtaining uniform field stress along the surface of the spacer but this technique may sometimes leads to very uneven shapes. In this study, a functional graded material is designed for the standard cone type spacer to obtain uniform field stress along the surface of spacer to overcome the above problem. The grading of spacer is done with different permittivities. Electric field is computed for three cases namely grading to high, grading to low and U Shape. The metal inserts were tuned and stress is obtained in account of lower fields at the triple point junction and an improved uniform field distribution along the surface is obtained.