Electrical Safety

What is Portable Appliance Testing (PAT)?

• ATesting of electrical devices for safety before use✓
• BTesting of portable toilets
• CTesting of equipment portability
• DTesting of personal audio devices

Answer: PAT is a process of examining electrical equipment for faults that could cause hazards. It involves visual inspection and electrical testing to ensure user safety.

When must an electrical circuit be isolated before work?

• AOnly if the work appears dangerous
• BBefore working on or near live circuits or cables✓
• COnly if workers request it
• DNever; isolation is unnecessary

Answer: Isolation removes the energy source, preventing shocks and arcs. It is mandatory before electrical work. Appearing dangerous and worker request are insufficient; procedure must be followed.

What is the risk of working near overhead power lines on a construction site?

• ANo risk if you don't touch them
• BElectrocution from proximity arcs, especially with cranes or tall equipment✓
• COnly minor burns
• DThe risk is exaggerated

Answer: High-voltage overhead lines create arcs over distances (typically 3–5 metres). Cranes and boom lifts can arc without direct contact, causing electrocution. Proximity alone is dangerous.

Before using an electrical power tool on a construction site, what should be checked?

• AThe cost of the tool
• BThe colour of the cable
• CPAT test status, cable condition, plug integrity, and that it is appropriate for the environment (e.g., wet areas)✓
• DThe user's name

Answer: Pre-use checks must verify PAT compliance, cable damage, plug safety, and environmental suitability. Cost, colour, and user name are irrelevant to electrical safety.

What is a Residual Current Device (RCD)?

• AA type of electrical cable
• BA safety device that cuts power instantly if an earth fault is detected✓
• CA circuit breaker that prevents overloading
• DA testing meter

Answer: RCDs (earth leakage breakers) compare current in and out. If they differ, power is cut in milliseconds, preventing electrocution. This is different from overload breakers.

Buried electrical cables can be present on construction sites. What precaution should be taken before excavation?

• AAssume there are no cables
• BExcavate carefully and monitor for cables
• CCall the utility company to locate cables or use safe digging practices like hand-digging and cable detection✓
• DNo precautions are necessary

Answer: Buried cables pose electrocution and fire hazards. The duty-holder must identify cable routes via utility companies or cable detection equipment before excavation.

What does 110V portable site lighting reduce compared to standard mains voltage?

• AThe brightness
• BThe shock hazard, making it safer for temporary construction site use✓
• CThe cost
• DThe cable length

Answer: 110V is a lower voltage standard for construction sites. It reduces shock severity if contact occurs, making it safer than 230V mains voltage, especially in wet conditions.

An electrical fault is discovered on a site, such as a damaged cable. Who should be notified and what should happen?

• AIgnore it and continue work
• BThe supervisor; the equipment should be isolated, labelled, and removed from service✓
• CThe worker should attempt to repair it
• DWait until the end of the day to report it

Answer: Faulty equipment must be isolated immediately (tagged 'Do Not Use') and removed from service. Continued use, attempted repair, and delayed reporting all create electrocution hazards.

Under UK law, who is responsible for ensuring that electrical equipment on a construction site is safe?

• AThe worker using the equipment
• BThe equipment manufacturer only
• CThe employer (duty-holder), who must ensure safe provision, maintenance, and use✓
• DThe HSE

Answer: HSWA 1974 and the Electricity at Work Regulations 1989 place duty on employers to provide safe equipment, maintain it, and ensure competent use. Manufacturers and workers support this but cannot substitute.

What should be done if a worker receives an electrical shock on site?

• ALeave them to recover alone
• BDisconnect the power source, call emergency services (999), and provide first aid if trained✓
• CAssume they are unharmed if conscious
• DMove them immediately to a distant location

Answer: Immediate action: disconnect power, call 999, administer CPR/first aid if trained, and keep the person warm. Never assume shock effects are absent; internal injuries are possible.

What is the primary purpose of an RCD (Residual Current Device) on a construction site electrical system?

• ATo save electricity costs
• BTo detect leakage current (earth leakage) and quickly disconnect the circuit, preventing electrocution if a person touches a live conductor or earth fault✓
• CTo prevent overheating of cables
• DTo extend cable lifespan

Answer: RCDs detect leakage current (as low as 30mA) and trip within milliseconds, limiting the duration and severity of electric shock. Cost savings, heat prevention, and cable lifespan are incidental. Electrocution prevention is the core function.

Why is 110V reduced voltage preferred for portable electrical tools on construction sites rather than 230V mains voltage?

• AIt is cheaper to install
• B110V reduces the severity of electric shock if contact occurs; the voltage difference between 110V and earth is lower, reducing current and heart fibrillation risk✓
• CIt provides more power to tools
• DIt requires no RCD protection

Answer: 110V step-down reduces shock severity compared to 230V because the voltage-to-earth is only 55V maximum. This is a risk reduction measure, not elimination. RCD protection still applies. Cost and power are secondary.