The Deadly Reality of Electrical Hazards

Electricity is silent, invisible, and unforgiving. According to HSE statistics, nearly 10% of all fatal accidents in the UK construction industry are caused by electrical faults, with around 1,000 electricity-related injuries reported annually across all sectors.

What makes electrical hazards particularly dangerous is their invisibility. You can't see, smell, or hear electricity—until it's too late. A moment's inattention around live electrical equipment can result in severe burns, cardiac arrest, or death.

Common Electrical Hazards on Construction Sites

Overhead Power Lines

Contact with overhead power lines is one of the most common causes of electrical fatalities on construction sites. Cranes, excavators, tipper trucks, scaffolding, and even ladders can come into contact with lines carrying thousands of volts. You don't even need direct contact—electricity can arc across air gaps, especially in damp conditions.

Underground Cables

Every year, workers are killed or seriously injured striking buried cables during excavation work. Even cables that should be "dead" may still be energised, and cable locations shown on drawings may be inaccurate.

Portable Electrical Equipment

Power tools, leads, and extension cables take a beating on construction sites. Damaged cables, missing earth connections, and wet conditions create serious risks. The combination of metal tools, standing water, and damaged equipment is potentially lethal.

Temporary Electrical Installations

Site electrical supplies are exposed to harsh conditions—mechanical damage, dust, water, and constant modification. Unlike permanent installations, temporary systems often lack the protection and maintenance of building electrical systems.

Working Near Existing Electrical Installations

Refurbishment and renovation work often takes place near live electrical equipment. Accidental contact with concealed cables in walls and floors is a common cause of electric shock.

The Legal Framework

Electricity at Work Regulations 1989 (EAWR)

The primary legislation requiring:

• Electrical systems to be constructed and maintained to prevent danger
• Work on or near electrical systems to be carried out safely
• Persons to be competent to prevent danger and injury

BS 7671 (IET Wiring Regulations)

The UK standard for electrical installations, currently BS 7671:2018+A3:2024 (18th Edition with Amendment 3). Construction sites are classified as special locations requiring specific precautions due to the increased risk from mechanical damage and harsh conditions.

CDM Regulations 2015

Require electrical hazards to be considered in design and planning, with information about electrical services included in the pre-construction information pack.

Key Safety Measures

Reduced Voltage Systems

On UK construction sites, 110V centre-tapped earth (CTE) systems are standard for portable tools. This limits the maximum voltage to earth to 55V, significantly reducing shock severity. All portable equipment on site should be 110V unless there's a specific, risk-assessed reason to use 230V.

Residual Current Devices (RCDs)

RCDs detect earth faults and disconnect the supply rapidly—typically within 40 milliseconds. They should be:

• Rated at 30mA maximum for personal protection
• Tested regularly (test button should be pressed monthly)
• Used for all socket outlets on site

Important: RCDs don't prevent all shocks—they limit the duration. Contact between live and neutral without earth involvement won't trip an RCD.

Equipment Inspection and Maintenance

All portable electrical equipment should be:

• Visually inspected before each use by the user
• Formally inspected at regular intervals based on risk
• Tested by a competent person (PAT testing)
• Removed from service immediately if damaged

Cable Protection

• Route cables overhead where possible
• Use cable protectors or bury cables where crossing trafficked areas
• Never run cables through water
• Use armoured cables for fixed installations
• Avoid trailing leads wherever possible

Working Near Overhead Power Lines

Before work begins near overhead lines:

1. Contact the network operator to identify the voltage and get advice
2. Establish safe clearance distances:
   • Low voltage (up to 1kV): 1 metre minimum
   • 11kV: 3 metres minimum
   • 33kV: 6 metres minimum
   • 132kV and above: 9 metres minimum
3. Consider whether lines can be diverted or isolated
4. Install goal posts or barriers to prevent plant encroaching on exclusion zones
5. Brief all workers including delivery drivers

Excavation Near Underground Cables

Before any excavation:

1. Obtain utility drawings from the network operator and other services
2. Use cable locating equipment (CAT and Genny) to trace cables
3. Hand dig trial holes to confirm cable positions
4. Assume cables are live until proven otherwise by the network operator
5. Don't use mechanical excavators within 500mm of known cable locations
6. Use insulated hand tools when hand digging near cables

Isolation Procedures

Before working on electrical equipment:

1. Identify the circuit and all possible sources of supply
2. Isolate at the appropriate point
3. Secure the isolation (lock off/lock out)
4. Prove the supply is dead using an approved voltage indicator
5. Test the voltage indicator before and after use
6. Earth where necessary
7. Only then permit work to begin

Never work on or near live electrical equipment unless it's absolutely unavoidable and a specific safe system of work is in place with appropriate precautions.

Emergency Response

If someone receives an electric shock:

1. Don't touch them directly—you may become a second casualty
2. Isolate the supply if you can do so quickly and safely
3. If you can't isolate, use a non-conducting object to push them away from the source
4. Call emergency services immediately
5. If they're not breathing, begin CPR and use an AED if available

Competence

Only competent persons should work on electrical systems. Competence means having:

• Adequate knowledge and experience of electricity
• Understanding of the specific work to be undertaken
• Ability to recognise when it's unsafe to proceed
• Knowledge of emergency procedures

For construction site electrical installations, this typically means a qualified electrician with experience of temporary systems and BS 7671 requirements for construction sites.

Conclusion

Electrical hazards deserve respect. The consequences of getting it wrong are severe—electrocution can kill in an instant, and even non-fatal shocks can cause lasting injuries including cardiac problems, burns, and psychological trauma.

Include electrical hazards in your RAMS documents, specify appropriate controls, and ensure only competent persons work on electrical systems. It's one area where cutting corners can have fatal consequences.