Comparative Testing of Helical & Concentric Shed Profiles on HV Bushings by Roger Hedlund

Polymeric insulators used on HV bushings are available in different variants, either molded in sections with concentric shed profile or extruded in a helical-shaped continuous process. The silicone rubber material can either be LSR or HTV, where the former is used for concentric shaped insulators while the latter can be used for both types. This presentation reports on findings from full-scale comparative testing of these variants performed on commercially available transformer bushings during heavy rain and after complete loss of hydrophobicity