high-voltage electric switching gear used for rapid connection and disconnection of electric circuits operating under normal conditions, and also of load circuits and no-load power lines and transformers. Under emergency conditions a load disconnect must also withstand the short-circuit current of the circuit in which it is installed; in such situations it must have sufficient dynamic and thermal strength to withstand the let-through short-circuit currents flowing through its current-carrying system.
Since load disconnects are not intended for interruption of short-circuit currents, their arc-arresting parts and drive mechanisms are much simpler and their cost lower than those of other high-voltage breakers. The most common arc arresters in load disconnects are those that use a solid arc-arresting substance, elegaz (sulfur hexafluoride), as well as vacuum arc arresters and those with magnetic blowout. High-voltage fuses are usually installed in series with load disconnects to protect electrical equipment from short-circuit currents. In a radial distribution network a main breaker is often installed at the origin point of the transmission line as a protective device, and load disconnects are installed on the branches. In the event of a short circuit in one of the branches, the main breaker opens, followed by the lead disconnect of the damaged branch; the main breaker can then be reclosed and power supplied to all other users. Other network connection circuits with load disconnects are also in use.
REFERENCESChunikhin, A. A. Elektricheskie apparaty. Moscow, 1967.
Lisovskii, G. S. , and M. E. Kheifits. Glavnye skhemy i elektrotekhnicheskoe oborudovanie podstantsii 35–500 kv. Moscow, 1970.
Poltev, A. I. Elegazovye apparaty. Leningrad, 1971.
A. M. BRONSHTEIN