In electric power distribution, a busbar is a metallic strip or bar, typically housed inside switchgear, panel boards, and busway enclosures for local high current power distribution. High current busbars are prone to overheating, due to changes in the material structure from overloading. Above a certain current, the resistive losses exceed the cooling of the busbar, causing a temperature rise of the bus, hence increasing the resistivity, which in turn increases the resistive losses and so on. A so-called thermal runaway occurs that can only be stopped by reducing the current in the circuit.

The same can be said for other bolted electrical connections where high currents can change the resistance at the joint and thus cause a thermal runaway and perhaps a fire. Typical applications include electrical motors, solar panels, etc