Electrical Faults #
Types #
- Short circuit: two conductors at different voltages make contact. Enormous current → fire risk.
- Overload: current exceeds rating but less than short circuit. Gradual overheating → long-term fire risk.
- Earth fault: live conductor contacts equipment casing. Risk of electrocution.
Protection Devices #
- Fuse: wire melts at overcurrent (single-use)
- MCB (circuit breaker): magnetic trip (short circuit, instant) + thermal trip (overload, delayed). Reusable.
- RCD (residual current device / “safety switch”): detects current leaking to earth. Trips at 30 mA — saves lives.
Coordination Rule #
$$I_B \leq I_n \leq I_z$$\(I_B\) = operating current, \(I_n\) = protection rating, \(I_z\) = cable capacity.
Conclusion #
Every fault type has its specific protection: MCB for short circuits and overloads, RCD for earth faults. Good protection is the difference between a safe installation and a disaster.
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