High voltage electrical systems on construction sites include substations, switchgear, transformers, and HV cables carrying 11kV and above. These systems can kill at distance through arcing without direct contact. Only authorised and competent persons may work on or near HV equipment. This talk explains the HV hazards, the exclusion zone requirements, and the rules that protect every person working near HV infrastructure.
Key Hazards
Fatal electrocution from contact with or proximity to energised HV equipment
Arc flash causing catastrophic burns and blast injuries from HV fault energy
Induced voltage in nearby metalwork and equipment from HV electromagnetic fields
Unauthorised access to HV enclosures by untrained construction workers
Control Measures
Maintain exclusion zones around all HV equipment as specified by the asset owner and GS6 guidance.
Ensure all HV enclosures, substations, and switchrooms are locked and clearly marked with danger signs.
Only persons holding a current HV authorisation may access, operate, or work near HV equipment.
Use approved safety rules and a formal switching programme for all HV isolation and switching operations.
Ensure safety keys, locks, and earthing equipment are maintained in good condition and tested regularly.
Brief all site personnel on HV exclusion zones, danger signs, and the prohibition on unauthorised access.
Report any damage to HV fencing, enclosures, or warning signs to the site electrical engineer immediately.
Ensure crane operations, scaffolding, and MEWPs maintain safe clearance from all HV equipment.
Carry out a risk assessment before any construction work within the HV safety zone boundary.
Emergency / Rescue
If someone contacts HV equipment, do not touch them. Call 999 immediately and request the HV supply to be isolated by the network operator. Do not approach within the safe distance until confirmed de-energised.
Remember
Only persons with current HV authorisation may access or work near high voltage equipment
Maintain exclusion zones around HV equipment as the asset owner and GS6 guidance specify
All HV enclosures and switchrooms must be locked and marked with clear danger warning signs
Cranes, scaffolding, and MEWPs must maintain safe clearance from all HV infrastructure
Report any damage to HV fencing, enclosures, or warning signs to the electrical engineer immediately
Applicable Legislation: Electricity at Work Regulations 1989 · HSE GS6 (Avoidance of Danger from Overhead Lines) · Health and Safety at Work etc. Act 1974 · CDM Regulations 2015