Switchgear combines switching, isolation, protection, control and measurement equipment in an assembly. Depending on the system, it can include busbars, circuit breakers, disconnectors, earthing switches, fuses, instrument transformers, protective relays and surge arresters. These devices connect normal circuits and isolate equipment during maintenance or faults.
Specify switchgear for system voltage, continuous current, short-circuit withstand, interrupting duty, insulation level, internal-arc risk and installation environment. Equipment that breaks fault current must have an interrupting rating at least equal to the available current at its terminals. Safe operation also depends on protection coordination, interlocks, accessible isolation, working clearances and maintenance.
