Plant Services - March 2008 - (Page 34)

hen a problem occurs in an electrical distribution system, the ﬁ rst question usually is, “Where?” Which panel, what circuit, what component? A thermal imager probably can provide the fastest answer to this question. Scan the electrical components, look for abnormal temperatures and zero in. e follow-up question, “What happened?” is answered by a combination of technician and electrician expertise, and by various electrical tests and measurements. But, that’s another story. It’s a myth that every electrical hot spot is the result of a loose connection. First, though, you need to identify problems within the electrical distribution system, both when trouble has hit and in advance, through routine preventive maintenance. Loading, safety, emissivity Modern thermal imagers are rugged, easy to use and more affordable than models from even just a few years ago. ey’re a realistic solution for routine electrical maintenance. A qualiﬁed person points the device at the equipment and scans the immediate area, looking for temperature anomalies that appear on a live, false-color image revealing where the equipment is emitting heat. ermal images can be captured and uploaded to a computer for closer analysis, reporting and future trending. Imagers are easy to use, but they’re most eﬀective in the hands of qualiﬁed technicians who understand both electri34 cal measurement and the equipment being inspected. e following three points are especially important. First, the electrical equipment being inspected must be under at least 40% of its nominal load if a thermal imager is to detect problems eﬀectively. If possible, test under maximum load conditions for best results. Second, the electrical measurement safety standards as speciﬁed in NFPA 70E apply. Anyone standing in front of an open, live electrical panel must not be wearing jewelry, a watch or carrying keys, and he or she must use personal protective equipment (PPE) (Figure 1). Depending on the situation and the incident energy level (bolted fault current) of the equipment being scanned, this might include: • A ﬂame-resistant, long-sleeved shirt and workpants • Category-rated leather-over-rubber gloves • Leather work boots • Arc ﬂash-rated face shield, hard hat, hearing protection • Arc ﬂash-rated suit, hood and gloves Always make sure you know the proper PPE for the environment in which you will be working. For PPE guidelines, reference NFPA Standard 70E, Tables 130.7 (c)(9)(a), (c)(10) and (c)(11). e third point is called emissivity, a concept that describes how well an object emits infrared energy, or heat. is variable aﬀects how accurately a thermal imager can measure a surface temperature. Materials emit infrared energy in diﬀerent ways, and their speciﬁc emissivities are ranked on a scale of 0.0 to 1.0. Greater emissivity yields more accurate temperature readings. Objects exhibiting high emissivity emit thermal energy M .PLANTSERVICES. http://www.plantservices.com

Table of Contents Feed for the Digital Edition of Plant Services - March 2008

Plant Services - March 2008 Contents From The Editor Letters The PS Files Up and Running Crisis Corner What Works Asset Manager: Enterprise Thinking Technology Toolbox: Hydrogen In Action Cover Story: Get Real Electrical: Reliable Distribution Power Transmission: When the Belt Breaks Web Hunter: Tooting Horns In the Trenches Product Picks Classifieds Fast Facts Energy Expert: Energy versus Sustainability

Plant Services - March 2008

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