Electrical Safety
Electrical Safety tests shock protection, protective devices, safe isolation and emergency response.
Core rules
- Current through the body is the hazard: I = V/R. Dry skin may be about 1 kΩ; wet skin is far lower, so the same voltage is much more dangerous.
- Earthing gives a low-resistance fault path; an RCCB/ELCB detects residual current and is set at 30 mA for personnel protection in many socket circuits.
- An MCB protects against overload and short circuit, not against earth leakage; an RCCB does not replace it.
- Use lockout/tagout, prove dead with a tested voltage detector, and treat conductors as live until tested.
- For electrical fires use CO₂ or dry powder, never water. For a shocked victim, isolate the supply before touching the person and start CPR if breathing is absent.
Worked example
A person contacts a 230 V live part while standing on wet ground, giving a body resistance of 1000 Ω. Body current = 230/1000 = 0.23 A = 230 mA, well above the let-go threshold and potentially fatal. A 30 mA RCCB monitoring the circuit should detect the residual current and disconnect the supply. If the person were isolated from earth, the current path might not exist, but that is not a safe assumption.
Traps
Do not say an RCCB protects against overload; do not use water on an electrical fire; do not touch a victim still in contact with live parts; and do not rely on rubber gloves as a substitute for isolation.