Preventing Failures in Outdoor Distribution-Class Metalclad Switchgear

Failure of the insulation in distribution- class metalclad switchgear may release large amounts of energy resulting in an explosive hazard to adjacent equipment and personnel. Many such failures have occurred in older outdoor and generating station switchgear within Ontario Hydro. The failures have often been caused by partial discharge (PD) activity and surface tracking which destroy organic bus support insulation. Test methods have evolved to help locate deteriorating insulation in the field, and to qualify new insulation systems. The life of the switchgear can often be extended by incorporating appropriate preventive maintenance.