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Working in high-voltage areas and switchyards demands strict attention to safety and adherence to specific ground rules.
This post highlights the essential regulations and best practices that every engineer, technician, and maintenance worker must follow to prevent accidents and ensure a safe, hazard-free environment.
Executing any job in High-voltage (HV) environments demands a rigorous understanding of hazards and strict adherence to safety protocols. As a result of this, only properly authorized personnel may enter these areas. This guide outlines the fundamental rules for ensuring safety in such locations.
Never enter a substation without the following PPE:
– Safety Helmet
– Long Sleeve Shirt and Long Trousers
– High-Visibility Vest or Shirt
– Safety Footwear
– Safety Eyewear
– Protective Gloves (carried on a clip)
Securing the Substation
In high voltage areas, unauthorized access must be prevented by strictly controlling entry points.
When entering, unauthorized persons must be restricted. Also, doors and gates must be closed and locked immediately after use.
When leaving, the last person to exit the station must ensure all doors and gates are locked and reset any security alarms.
Before starting any task, a hazard assessment must be conducted. Key hazards include:
1. Safe Distances from Energized Conductors
When in high-voltage areas, you should always maintain a safe distance from exposed HV conductors to prevent serious injury or fatality.
General Rule: It is important to stay at ground level and keep all tools and equipment below shoulder height.
Equipment Risks: Never use metal measuring tapes, rather, use non-conductive alternatives. Furthermore, avoid using ladders or long objects without proper control; that is, ensure such objects/equipment are kept at a safe distance from the energized conductors.
Fire Safety: Note that fire extinguishers for electrical fires are for low-voltage use only and hence, must not be used on HV equipment.
Covered Conductors: Treat any conductor covered with tape or fabric as an exposed HV conductor.
2. Understanding ‘No-Go’ Areas
High Voltage Cages (fully enclosed areas with exposed conductors) are strictly off-limits unless isolated under an Access Authority. Thus, it is crucial to report any unlocked cages immediately.
3. Vehicle and Mobile Plant Safety
Vehicles under 2.4m are safe for designated roadways. In the case of taller vehicles or off-road movement, ensure to consult a Mobile Plant Assessment professional.
Mobile Plant (Cranes, etc): These can easily move gradually on safe and secure approach distances. Safe routes must also be particularly established and adhered to.
AC currents in HV cables create electric and magnetic fields that can induce voltages in nearby objects.
Personal Risk: Workers can experience minor shocks from static discharge. Because of this, persons in the area must ensure they are not wearing, carrying any device or instrument that could greatly amplify the magnitude of this shock. And, those with medical implants, such as pacemakers, should have a proper consultation with their doctor.
Earthing Objects: Extended metallic structures and large vehicles in areas of high induction must be grounded to the substation earthing system.
Refueling: This must be done away from energized cables. For stationary equipment, use a static bonding kit to prevent sparks.
Isolated equipment can still have dangerous induced voltages from nearby live circuits, and so, Bonding Leads are used to create an equipotential zone and discharge capacitive voltages.
Requirements: A bonding lead must have a minimum cross-section of 35mm² copper and be attached with an appropriate clamp (e.g., MT815S). Moreover, it must not be yellow to avoid confusion with fault-rated equipment.
Application: When applying or removing a bonding lead, keep your body behind the lead and away from the conductors so as to avoid integrating yourself into the circuit.
6. Navigating Enclosed Spaces
Gas-Insulated Switchgear (GIS) buildings may have site-specific risks like gas discharge or moving parts. Therefore, always review site-specific risk assessments and signs before starting work.
The substation earthing system is designed to maintain equipotential conditions; thus, any damage to it can create hazardous voltages.
System Integrity: Do not approach, touch, or attempt to repair a damaged earthing system. Instead, report any damage immediately.
HV Equipment Earths: Work on earth connections may only be done after the equipment is isolated and proven dead.
Voltage Rise & Transferred Potentials: Never connect external equipment to the substation fence or grid, as hazardous voltages can be transferred.
Excavation: An authorized Excavation Permit is required. In addition, use non-destructive methods near buried services and employ a spotter. Also, bridging leads for the earth grid may be required and must be handled by authorized personnel.
8. Working Near HV Cables and Sealing Ends
HV cables can retain hazardous voltages if their earth connections are compromised. Work on cable earthing may only be performed after the cable is isolated and proven safe for work.
Electrical safety forms the bedrock of secure environments, yet often
Building a truly safe electrical system starts beneath the surface. Di
