Mechanical Forces and Thermal Effects in Substation Equipment Due to High Fault Currents

Mechanical forces and thermal effects produced by high fault currents can damage or destroy substation equipment. This damage is a serious safety issue for a number of reasons. All substation equipment can suffer damage from mechanical forces caused by short circuits. The short-circuit forces on a conductor are added to the other forces to produce a total force, which must be less than the minimum yield stress of the conductor material. Flexible conductor buses may be constructed as strain buses, suspended from insulator strings. When short-circuit forces increase, force safety devices (FSDs) can mitigate pinch-force effects. Cables are subject to thermal damage from prolonged exposure to short-circuit currents. The internal arcing fault-withstand capability of gas-insulated substations (GIS) is based on the thickness of the metal walls and the gas pressure, and is thus not easy to upgrade.