Electrical enlightenment

In brief:

• The maintenance function is a significant determinant to the efficiency and reliability of an electrical distribution system.
• Because of its universal applicability, electricians need to comply with all of the requirements in NFPA 70E, not just those one feels are relevant.
• The smart grid will require plants to be more proactive in monitoring and controlling electrical consumption.

Plant personnel have little control over the electrical supply upstream of the service entrance, but complete control over the distribution system within the plant. Yet many plants find themselves in the dark about electrical safety and system maintenance.

Solving an electrical distribution problem shouldn’t be a case of stumbling around blindly seeking diagnostic data. Instead, shine some light on the hardware components themselves. You might find obvious defects in cable routing or in panel layout. While you’re at it, it might be worthwhile to update your current single-line diagram to replace an out-of-date version.

Safety issues also need to be illuminated, as electrical systems carry not only power, but potential hazards, as well.

Figure 1. A panel cluttered as a result of repeated equipment and process upgrades can complicate maintenance and introduce potential hazards. (B. Miller Engineering)

“While arc flash gets a lot of attention, there are still electric shock and fire hazards in many facilities,” says Ben Miller, president of B. Miller Engineering (www.bmillerengineering.com) in Deerfield, Illinois. “These are the result of older systems that have been modified over the years and have exposed live conductors, excessive box and conduit fill, or inadequate equipment short-circuit ratings resulting from previous power system upgrades (Figure 1). Proper employee training often is overlooked as an important step to ensure that systems operate properly and safely. Downtime caused by operator error or accidents can be extremely costly.”

“Personal protective equipment, safety category ratings and arc flash calculation are,” says Frank Healy, Power Quality Products Manager at Fluke Corp. (www.fluke.com), “extremely important to plant maintenance personnel, as well as to engineers. In general, avoid working power live unless it’s necessary to troubleshoot performance. If live electrical work is required, carry appropriate liability insurance. Only qualified personnel are permitted to conduct live electrical work, and then only after conducting an arc flash survey and while wearing personal protective equipment and using measurement tools that are appropriately rated for the electrical environment.”

Figure 2. The presence of cobwebs in an electrical panel might be indicative of negligent maintenance practices. (EMP Engineering Services)

Figure 3. Mold growing in a panel might lead to carbon tracking and the problems that brings. (EMP Engineering Services)

Joseph Weigel, product manager at Schneider Electric (www.us.schneider-electric.com), says he’s spoken with thousands of customers and knows a bit about their current practices relative to their electrical distributions systems. “There’s one common universal problem many of these facilities face in their electrical systems,” he explains. “That is the lack of funding for, or lack of attention to, routine electrical system maintenance. Lack of maintenance ultimately will lead to failures that can interrupt production or operational processes, and it poses a serious safety hazard, as well.”

Douglas K. Smithman, P.E., president of EMP Engineering Services (www.empes.com), offers one easy-to-do answer: “Infrared inspections and periodic connector tightness checks are common, but cleanliness often is overlooked,” he says. “Cobwebs and using cabinets to store spare part and documents provide a backbone for dust accumulation and eventual problems with carbon tracking and failures.” (Figure 2 and Figure 3)

Thermal imaging has become commonplace in many daily plant operations, says Rick Maday, product manager at Fluke (www.fluke.com/irwindows). “It’s no longer left to a simple yearly inspection,” he explains. “As the frequency of IR inspections increases, so too does the exposure to and risk of arc flash. Enclosures must be opened to scan with IR and doing so greatly increases the likelihood of an arc flash explosion. IR windows can mitigate this risk. They let infrared scans be performed without opening enclosures, virtually eliminating the risk of an arc flash.”

Weigel also says, if he could choose one thing to help improve electrical system safety and reliability in most facilities, it would be to exercise more diligence about electrical maintenance and testing of electrical system components, and standards from the National Fire Protection Assn. (NFPA, www.nfpa.org) are a good place to start. “The standard NFPA 70B (Recommended Practice for Electrical Equipment Maintenance — 2006) is a useful guide to electrical equipment maintenance,” suggests Weigel. “Other sources, such as the original equipment manufacturer’s O&M documentation, also are useful to establish proper maintenance practices and intervals.”