Working on Live Circuits
Working near energized circuits.
Working on live circuits means actually touching energized parts. Working near live circuits means working close enough to energized parts to put you at risk even though you may be working on de-energized parts.
Common tasks where you need to work on or near live circuits include:
- taking voltage and current measurements;
- opening and closing disconnects and circuit breakers;
- racking circuit breakers on and off the bus;
- removing panels and dead fronts; and
- opening electric equipment doors for inspection.
There should be standard written procedures and training for these common tasks. For instance, when opening and closing disconnects, use the left-hand rule when possible (stand to the right side of equipment with a disconnect on the right, and operate the disconnect with your left hand). For other situations where you might need to work on or near live circuits, your employer should institute a written live-work permit system, which must be authorized by a qualified supervisor.
Lineman working on a power line.
A 40-year-old male meter technician had just completed a 7-week basic lineman training course. He worked as a meter
technician during normal working hours and as a lineman during unplanned outages. One evening, he was called to repair a
residential power outage. By the time he arrived at the site of the outage, he had already worked 2 hours of overtime and worked 14 straight hours the day before.
At the site, a tree limb had fallen across an overhead powerline. The neutral
wire in the line was severed, and the two energized 120-volt wires were disconnected. The worker removed the tree limb and climbed up a power pole to reconnect the three wires. He was wearing insulated gloves, a hard hat, and some safety goggles.
He prepared the wires to be connected. While handling the wires, one of the energized wires caught the cuff of his left glove and pulled the cuff down. The conductor contacted the victim's forearm near the wrist. He was electrocuted and fell backwards. He was wearing a climbing belt, which left him hanging upside down from the pole. Paramedics arrived 5 minutes after the contact. The power company lowered his dead body 30 minutes later.
Several factors may have contributed to this incident. Below are some ways to eliminate these risk factors:
- Ask for assistance when you are assigned tasks that cannot be safely completed alone. The task assigned to the
victim could not have been done safety by only one person.
- Do not work overtime performing hazardous tasks that are not part of your normal assignments.
- Employees should only be given tasks they are qualified to perform. All employees below the journeyman level should be supervised.
Live-Work Permit System
A live-work permit should, at least, contain this information:
- a description of the circuit and equipment to be worked on and the location,
- explanation why the work must be done "live"
- date and time covered by the permit
- a description of the safe work practices to be used
- results of shock hazard analysis and determination of shock protection boundaries
- results of flash hazard analysis and determination of the flash protection boundary
- PPE needed to safely perform the job
- who will do the work and how will unqualified persons be kept away
- evidence of completion of job briefing, including discussion of job-specific hazards
- energized-work approval signatures (authorizing or approving management, safety officer, owner, etc.)
A company was contracted to install wiring and fixtures in a new office complex. The third floor was being prepared in a
hurry for a new tenant, and daily changes to the electrical system blueprints were arriving by fax. The light fixtures in the
office were mounted in a metal grid that was fastened to the ceiling and properly grounded.
A 23-year-old man apprentice electrician was working on a light fixture when he contacted an energized conductor. He came
down from the fiberglass ladder and collapsed. Apparently, he had contacted the "hot" conductor while also in contact with
the metal grid. Current passed through his body and into the grounded grid. Current always takes a path to the ground. In
this case, the worker was part of that path.
He was dead on arrival at a nearby hospital. Later, an investigation showed the victim had cross-wired the conductors in
the fixture by mistake. This incorrect wiring allowed electricity to flow from the live circuit on the completed section of
the building to the circuit on which the victim was working.
Below are some safety procedures that should have been followed in this case. Because they were ignored, the job ended in
- Before work begins, all circuits in the immediate work area must be shut off, locked out, and tagged out- then tested
to confirm they are de-energized.
- Wiring done by apprentice electricians should be checked by a journeyman.
- Supervisors should always review changes to an original blueprint in order to identify any new hazards the changes
Safe Work Practices
To work on or near live parts, you must do the following:
- Have a written live-work permit for the work to be done.
Wear the right PPE to protect against electric shock and arc flash. Never wear clothing made from synthetic materials, such as acetate, nylon, polyester, polypropylene, or rayon - alone or combined with cotton. Such clothing is dangerous because it can burn and melt into your skin.
The PPE that is needed depends on the type of electric work being done. The minimum PPE required while working on line circuits would be an untreated natural fiber long-sleeve shirt and long pants plus safety glasses with side shields. Depending on the voltage and the electric task to be done, different types of PPE are required. Fire-resistant protective clothing can include multi-layer flash suit jacket and pants, wraparound face shield, double-layer switching hood, voltage-rated gloves with leather protectors, electrically rated hard hats, and so forth. [(See Table 130.7(C)(15)(A)(b) Arc-Flash Hazard PPE Categories for A/C systems, Table 130.7(C)(15)(B) Arc-Flash Hazard PPE Categories for D/C Systems, and Table 130.7(C)(16) Personal Protective Equipment (PPE)) NFPA 70E, 2015 Edition].
Use the proper type of protective equipment, such as insulated tools and/or handling equipment that is rated for the voltage. These can include insulated fuse or fuse holding equipment, nonconductive ropes and handlines, fiberglass-reinforced plastic rods, nonconductive portable ladders (such as, fiberglass), protective shields, rubber insulating equipment, voltage-rated plastic guards, and so forth.
A lineman (the victim) was killed after contacting a 17,400-volt charge switch. The victim was part of a three-man crew
replacing cables under a switch cabinet. At the time of the accident, the crew was feeding a new cable under the concrete foundation pad below the cabinet. As one worker pushed the cable under the foundation, the victim looped the cable inside the foundation under the cabinet. The victim was using a hot stick to loop the cable but was not wearing his hard hat when his head came either in close proximity to or contacted the charged switch. Crewmembers saw a flash and came around the switch cabinet to where the victim was located. He was found slumped partially in the cabinet. A crewmember used a hot stick to move the victim away from the cabinet and then began CPR. Emergency medical services transported the victim to a nearby hospital where he was declared dead from injuries associated with high-voltage electrocution.
Based on the findings in the investigation, to prevent similar incidents, employers should:
- Ensure workers use personal protective equipment and enforce its use.
- Ensure workers are capable of recognizing and avoiding hazardous situations.
- Emphasize de-energizing, isolating, or cover energized work areas whenever personnel need to work within high voltage danger zones.