Protection and Switchgear
Fuses, circuit breakers, relays and earthing that detect faults and isolate them quickly and selectively.
Protection systems must be reliable, selective (trip only the faulty section), fast, sensitive and economical. A protection scheme combines sensing (CTs and PTs), decision (relays) and interruption (circuit breakers or fuses).
Sub-topics (6)
Fuses
The simplest protection: a wire that melts when current exceeds its rating for long enough.
Circuit Breakers
Switches that automatically open on faults and can be reset — MCB, MCCB, ACB, VCB and SF6 breakers.
RCD and RCCB
Residual current devices trip when current leaks to earth — protecting people from electric shock.
Protective Relays
Relays that detect abnormal conditions and command breakers to trip — overcurrent, differential and distance protection.
Instrument Transformers
Current transformers (CT) and voltage transformers (PT/VT) scale high currents and voltages down for meters and relays.
Earthing and Grounding
Connecting equipment and system neutrals to earth for safety and protection operation.
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