A presentation at the PQ World 2002 Conference in October re-enforced the need to continue to make the electrical workplace a safer place to work in. While it would be ideal, it’s not always possible to de-energize electrical systems before working on them. A leading semiconductor manufacturer has established the concept of EEWF—Energized Electrical Work Friendly—by making electrical panels “touch-safe” when the covers are removed. The need to change the wiring configuration without de-energizing the entire panel comes from their need to convert or modify existing plants to accommodate process changes while still being chartered with meeting wafer-production commitments. This concept has raised other questions, such as maintaining the UL listing of modified equipment, but has been viewed by many as a step in the right direction.
One of several documents from different standards groups that addresses the topic is the “NFPA70B Recommended Practice Electrical Equipment Maintenance,” from which the following is extracted:
Section 7.1.1 Equipment should be de-energized for inspections, tests, repairs, and other servicing. Such maintenance tasks can be performed when the equipment is energized provided provisions are made to allow maintenance to be performed safely.
Section 22.214.171.124 Switchboards, panelboards, industrial control panels, and motor control centers that are likely to require examination, adjustment, servicing, or maintenance while energized, should be field marked to warn qualified persons of potential electric arc flash hazards. The marking should be located so as to be clearly visible to qualified persons before examination, adjustment, servicing, or maintenance of the equipment.
Section 7.3.3 As a general rule, no electrical apparatus should be worked on while it is energized. Work on or near energized conductors or equipment rated over 50 volts should be performed only when it is not feasible to de-energize, or when it would create a greater hazard to perform the work in a de-energized condition. When it is necessary to work in the vicinity of energized equipment, all safety precautions should be followed, such as roping off the dangerous area, using rubber blankets for isolation, and using rubber gloves and properly insulated tools and equipment. All insulating tools such as rubber gloves and blankets should be tested periodically. See 29 CFR 1910.137 “Electrical Protective Devices,” for the testing, care, marking, and use of rubber goods, such as insulating blankets, matting, covers, line hose, gloves, and sleeves.
Section 126.96.36.199 Prior to performing maintenance on or near live electrical equipment, NFPA 70E, Standard for Electrical Safety Require- ments for Employee Workplaces, should be used to identify the degree of personal protective equipment (PPE) required.
These concepts are applicable to conducting measurements for power-quality concerns, as well as for installing monitors for longer-term monitoring. The facility manager, who has just had a critical process interrupted due to a power quality disturbance, may not be willing to have the process interrupted again in order to connect the monitoring equipment on a de-energized circuit. Again, working on de-energized circuits is the preferred method, but that is not always feasible in the work place. But this doesn’t mean that safety should be compromised.
There have been occasions when electricians connect the power-quality monitor without reading the user’s guide to determine the proper connection method, do not wear proper personal protective equipment, and leave the panel off with the energized wires hanging out. Not only are they jeopardizing their safety and the safety of anyone else in the area, they are jeopardizing the operation of the facility as well. An accident is not something that just happens to someone else. They often happen to those who didn’t take the necessary precautions to make them preventable incidents.
The aforementioned semiconductor facility, which actively pursued an EEWF program for the past two years, managed to improve safety conditions for personnel who would have otherwise been exposed to energized electrical equipment, and had 1,000 fewer incidents throughout the corporation over the previous year. They saved money, too. Completion times for process tool installations or removals decreased, and reduction-power reliability issues associated with construction activities dropped to zero in the year following the panel retrofits. Safety is something that you cannot afford to not do. EC
BINGHAM, a contributing editor for power quality, can be reached at 732.287.3680.