Field Stress Control of a Functionally Graded Disk Type Spacer in a Gas Insulated Bus Duct with Metal Inserts

High voltage electric utilities are hindered with certain difficulties like high stress distribution and insulation damage that are needed to be taken care for reliable operation of the system. In a Gas Insulated bus duct, high field stress along the spacer surface especially at the contact point of the conductor, insulator and gas (called triple junction) is a major factor affecting the insulation strength. Research studies of shaping the spacer were found effective in controlling the stress distribution but found to be complicated in real time application. In this paper, functionally graded materials of disc type spacer with different permittivity are proposed for controlled field stress distribution at the spacer surface. Electric field calculations with different gradings from high to low and U shape are done. Properly shaped metal inserts are incorporated to have a uniform stress distribution along the spacer.