When working on Exposed Energized Electrical Equipment it is important to understand the hazards and what Personal Protective Equipment (PPE) to select.
With guidance from the NFPA 70E Standard for Electrical Safety in the Workplace it is understood that work on exposed energized electrical equipment should be limited to voltage measuring, troubleshooting, testing, infra-red scanning, ultrasound, or visual inspections by a qualified worker wearing the appropriate PPE for the task. Anything that falls outside of the these items requires the worker to put the equipment in an electrically safe working condition or fill out an energize work permit and get authorization from the required on-site personnel given authority to review and sign-off on energized electrical work permits.
When working on exposed energized electrical equipment it is important to understand the three main hazards that the worker is exposing themselves too.
The first hazard and the electrical hazard that currently kills the most workers in the U.S.A. each year is electrocution. It is important that each individual working on exposed energized electrical equipment selects at a minimum the proper voltage rated gloves anytime they are coming in contact with an exposed energized piece of equipment with either their hands, voltage probes, insulated tools, or any other equipment that might come in contact with an energized piece of equipment. This voltage rated PPE is required anytime personnel are inside the restricted approach boundary(This information can be found on arc flash labels on the equipment or in table 130.4(D)(a) of NFPA 70E 2018).
The second hazard generated from electrical equipment is the heat or arc flash hazard. With an industry change in the last 5 to 10 years of requiring employees to wear Fire-Retardant (FR) uniforms, the amount of workers dying from the heat/arc flash has dropped. Studies have found that in some cases the difference between life and death when an arc flash occurs, is if the personnel in the affected area had FR clothing on or not. The majority of personnel dying each year from the heat generated in an arc flash are people that did not wear any FR protection. FR clothing should be selected to exceed the incident energy calculated on the posted arc flash labels or if there aren’t any posted arc flash labels, table 130.7(C)(15)(a) from NFPA 70E 2018 should be referenced to assist in the selection of the required FR PPE.
The last of the three hazards is the blast hazard. A good way to determine the effects of the blast when an arc flash occurs have not been determined yet. The blast is not directly tied to the amount of heat available, but also is based on the voltage and amount of fault current present. Because at this point in time there is not a good way to calculate how large the blast is in different situations, most personnel in the industry draw the line at 40cal/cm^2 even though PPE can be purchased that is rated at over 100cal/cm^2. By not allowing personnel to work in areas with an incident energy over 40cal/cm^2 we are able to limit their exposure to the blast. The current PPE just offers protection from the fire and cannot protect against broken bones or other effects from the pressure that results in areas with large fault currents.
When working on Exposed Energized Electrical Equipment it is important to analyze the risk of each situation and employ the hierarchy of risk-control methods before proceeding with the work to try and limit the hazards that employees are being exposed to. After analyzing the situation the proper PPE can be selected for the job so that the work can be done safely.
Ryan Fecteau Electrical Engineer Switchgear Power Solutions Mobile: (920) 470-0415 Office: (920) 234-2500 www.switchgearpowersolutions.com