Electrical Safety
Electrical Safety tests shock hazards, earthing, protective devices, safe work practices, and emergency response.
Core rules
- Current through the body, not voltage alone, causes injury; contact resistance and path matter. Earth fault raises metalwork potential unless bonded.
- Earthing: equipment earthing gives a low-impedance fault path; system neutral earthing stabilizes voltage. Earth resistance is measured by fall-of-potential or loop tester.
- MCB protects against overload and short circuit; ELCB/RCCB detects residual current to earth; fuse melts on overcurrent. Select ratings with discrimination.
- Lockout/tagout isolates energy; test-before-touch; use insulated tools and PPE; work permit for high-voltage work.
- Electrical fire: use CO2 or dry powder, never water. First aid: isolate supply, call help, start CPR if trained.
Worked example
A 230 V supply feeds a faulty appliance with a 30 mA RCCB. If a person contacts live metal and 30 mA flows to earth, the RCCB trips within its rated residual current. The touch voltage depends on the earth path; a low-resistance earth keeps it lower.
Traps
An ELCB is not an overload protector. A fuse does not protect against all earth leakage. Do not reset a tripped protective device repeatedly without finding the fault. Do not assume rubber gloves are sufficient for high voltage.