Published on 10 Oct 2019 by ES Staff
The purpose of this document is to protect personnel when working on or near exposed energized electrical circuits and equipment.
First and foremost, working on unguarded energized equipment is not permissible. However, situations may arise that require energized work. In such cases, specific approval must be obtained and the following four hazards addressed:
- Shock and burn due to contact
- Electric arc burns caused by high energy electrical faults (arc flash)
- Damage to equipment due to arcing or short-circuited conductors
- Upset or shutdown of an operating unit
Personnel working on or near exposed energized electrical equipment must meet the requirements of "NFPA 70E Table 130.4(C): Standard for Electrical Safety in the work place" before beginning work.
- Only authorized personnel trained on the specific task and the hazards involved are permitted to perform work on energized conductors.
- Energized work within the Prohibited Approach Boundary is done only with the proper authorization on facility operations, and then only on rare occasions when it is absolutely necessary. In these situations, the following document should be followed:
- The facility "Permit For Electrical Work On Or Near Energized Circuits" needs to be filled out completely and approved.
- The I&E supervisor should directly supervise any work on energized equipment.
- Immediately prior to doing any work on energized equipment, a complete review of all safety aspects of the job must be made and a specific job plan is written for the task by the involved supervisor and the qualified electricians who will perform the work.
- Qualified workers should be positive they have received and understood instructions as to how the job is to be done before starting work. Each person receiving oral instruction covering the handling of energized equipment and circuits should immediately repeat the message to the one giving instructions so as to avoid misunderstandings.
- Qualified workers should read and sign the authorized "Permit For Electrical Work On Or Near Energized Circuits" before beginning work.
- No work on energized equipment should be attempted until there is assurance that it can be done safely. Always ensure at least "two layers" of protection between the hazard and personnel. For example, use insulated tools, but do not depend entirely on tool insulation for protection (e.g. do not grip bare wire with insulated pliers; grip insulated part of wire or connector).
- Details concerning work documents, testing and protective equipment, safety measures and other special precautions for a specific job will be specified on an individual basis and documented on the "Permit For Electrical Work On Or Near Energized Circuits".
- Avoid standing or sitting on wet surfaces while doing this type of work. Do not perform hot work if clothing or shoes are wet. Keep in mind that weather and body conditions can change during the course of the job.
- As in all electrical work, no metal ladders should be used.
- Before connecting dead conductors to live ones, the dead wires should be checked with a megger to assure absence of short circuits or grounds. An ohmmeter check is acceptable on low voltage circuits (less than 50 volts), but a megger must be used elsewhere.
- A standby person is required for all energized work.
- Appropriate PPE should be used, including proper PPE for the standby person to perform any task which may be required (e.g. switching).
- While the danger of electrical shock diminishes as voltages drop below 50 volts, even a six-volt battery circuit can inflict painful and severe thermal and/or flash burns when short circuited.
- The use of test equipment such as voltage testers, voltmeters and clamp-on ammeters. However, energized troubleshooting of 480 volt MCC equipment is not recommended. Wiring and component troubles (e.g. faults, overloads) that result in protective
device operation (i.e. fuses, circuit breakers, and overloads) should be subject to de-energized troubleshooting. The cause of a protective device operation should be located and corrected before re-closing the circuit. If test equipment is to
be used for troubleshooting energized circuits, precautions should be taken as follows:
- Electrical troubleshooting should be planned carefully and critically to ensure that the work can be done safety.
- Electrical troubleshooting should be done only by qualified persons who are trained to recognize the hazards that are, or may be present. These persons should also understand the proper protection required to guard against exposure. In addition, trained persons should know what emergency measures to take in the event of an unplanned event occurring while troubleshooting is being performed.
- The use of protective guards (insulators) when done while using approved protective equipment (e.g. installation of rubber protective blankets on hot buswork while wearing voltage rated gloves).
- The use of welding machines having an open circuit voltage not exceeding 100 volts DC and 80 volts AC.
- Connecting and disconnecting wires from plug-in guarded type terminal blocks (such as AMP "Termi-Blok" connectors). Connecting and disconnecting wires from screw type terminal blocks. This exemption applies ONLY to small gauge (No. 12 or smaller) wiring on nominal 120-volt AC circuits protected by 20 amp or smaller fuses or circuit breakers. Minimum PPE for these tasks is safety glasses and voltage rated gloves.
- Working within the prohibited approach boundary of a 120 volt - 20 amps protected control (relay) cabinet when all of the following requirements are met:
- Only qualified persons trained on the specific task and the hazards involved should be permitted to perform work within the prohibited approach boundary.
- Insulated tools, safety glasses and voltage rated gloves should be used to perform the task.
- Fuses located within the cabinet, when needing to be removed for energy isolation, should only be removed using an appropriate voltage rated fuse puller.