Key points to cover
- Always assume cables and electrical equipment are live until proven otherwise by a competent person
- Use 110V (CTE) reduced voltage tools on site — 230V tools are not suitable for construction environments
- Check overhead power lines before using cranes, MEWPs, tipper lorries, or scaffolding near them
- Locate underground cables using up-to-date utility plans and a cable avoidance tool (CAT) before digging
- Portable electrical equipment must be kept in a safe condition — on site that means regular inspection and testing (PAT)
- RCDs (residual current devices) provide additional protection but do not eliminate the risk of electric shock
Do's and don'ts
Do
- Use 110V tools and check for the yellow CTE plug
- Use a CAT and Genny before any excavation work
- Maintain safe distances from overhead power lines as per HSE guidance (minimum exclusion zones)
- Check RCDs are working by pressing the test button daily
- Report any tingling sensations or shocks from equipment immediately
Don't
- Never use 230V domestic tools on a construction site
- Never run cables through water or across walkways without protection
- Never attempt electrical repairs unless you are a competent electrician
- Never bypass or remove fuses, circuit breakers, or RCDs
- Never use metal ladders near live electrical equipment or overhead lines
Questions to check understanding
Q1: What voltage should portable tools operate at on a construction site?
Show the answer
110V via a centre-tapped earth (CTE) transformer. This limits the maximum voltage to earth to 55V, which significantly reduces the risk of a fatal shock.
Q2: What equipment should you use before digging to locate underground cables?
Show the answer
A cable avoidance tool (CAT) and signal generator (Genny), together with up-to-date utility drawings. The CAT detects electromagnetic signals from buried cables and pipes.
Q3: What should you do if someone receives an electric shock?
Show the answer
Do not touch the casualty. Isolate the electrical supply if you can do so safely (switch off, pull the plug). Call 999. If the supply cannot be isolated, use a non-conductive item to separate the person from the source. Begin CPR if they are unresponsive and not breathing.
Q4: What is the minimum safe distance from an overhead power line?
Show the answer
There is no single figure. HSE guidance GS6 says to plan and manage any work within 10 metres of an overhead line and to keep plant out of a safety zone at least 6 metres from the outermost wire on each side of the line. Always ask the line owner for the safe clearance distance before work starts.
This is general guidance for UK construction sites. Check it against your own risk assessment, method statement and the site before you deliver it.