High-Voltage Areas and Switchyards: Safety Rules When Working

High-voltage substations and switchyards are among the most dangerous places anyone can work. HV electricity can arc across air gaps without contact, and isolated equipment can still carry induced or stored voltage. These rules apply to engineers, technicians, contractors and anyone else entering an HV area.

Only authorised people may enter

• Only trained and authorised personnel may enter HV areas. Visitors must be escorted.
• Keep substation doors and gates locked. The last person out locks up and resets any alarm.
• Report any unlocked substation, damaged fence or missing danger sign immediately.

Wear the right PPE

• Safety helmet
• Long-sleeve flame-resistant clothing and long trousers
• Safety footwear
• Safety glasses
• Insulating gloves rated for the work being done
• High-visibility vest where vehicles move

Assess hazards before starting

Every job starts with a hazard assessment and a clear method statement. Confirm which equipment is live, which is isolated, and where the boundaries are.

Keep a safe distance from live conductors

• Maintain the required safe approach distance from all exposed live conductors.
• Keep tools, ladders and long objects under control and away from live parts.
• Do not use metal measuring tapes. Use non-conductive alternatives.
• Treat any conductor covered with tape or cloth as bare and live.
• Ordinary fire extinguishers must not be used on live HV equipment.

Use permit-to-work and lock-out

No work may start on HV equipment until it has been:

1. Switched off and isolated from every possible source of supply, including generators and back-feeds
2. Locked off, with danger notices fitted
3. Proved dead with an approved voltage detector
4. Earthed at the point of work
5. Covered by a written permit-to-work issued by an authorised person

Where equipment is fed from a DisCo network, coordinate the isolation with the utility before work starts.

Beware of induced and stored voltage

Live circuits nearby can induce dangerous voltages in isolated conductors, long metal structures and vehicles. Cables and capacitors can also hold a stored charge. Use correctly rated earthing and bonding leads to discharge and bond equipment, and position yourself so your body never becomes part of the circuit while applying them.

Protect the earthing system

• Never touch or attempt to repair a damaged substation earth. Report it.
• Work on equipment earths only after the equipment is isolated and proved dead.
• Never connect external equipment to the substation fence or earth grid without approval, as dangerous voltages can be transferred.
• Excavation near buried cables and earth grids needs a permit and careful digging.

Vehicles, cranes and mobile plant

Tall vehicles and cranes must follow approved routes and keep well clear of overhead conductors, with a dedicated spotter where clearances are tight.

Gas-insulated and enclosed switchgear

GIS rooms and SF6 equipment have their own hazards, including gas release. Follow the site-specific risk assessment and the manufacturer’s instructions.

Planning new HV equipment? Read our guide to planning high voltage switchgear installations.

Talk to Corustar

Corustar Technological Services is an electrical engineering contractor based in Ikeja, Lagos, working across Nigeria. See our HV/LV Switchgear Maintenance & Commissioning service, request a quote, or call +234 816 976 9672. For outages and faults, call our 24/7 emergency line on 0705 739 9297.