Specified current in emergency load switches

The authors deal with the problems which arise in the contacts of power switches at LV distribution systems, especially in cases where emergency loads cannot allow programmed power interrupts through the central distribution panels to perform maintenance. Dust and other local impurities accumulated on the metal surfaces deteriorate the contacts with the time and the switch´s ability to supply its specified current. An explanation of the contact deterioration mechanism is attempted, and a solution of the maintenance problem is suggested: a design of a bypass supply system, including isolators and automatic switches. The proposed system was tested in actual industrial conditions, namely in hospitals, where maintenance is an awkward procedure, and proved to perform adequately