Tips & News - January 2012

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experienced one momentary outage per year (both during summer storms) that were caused by lightning. In both cases, the stroke magnitude was greater than 100 kA,” says Maddox. “The Vaisala data indicates that GTC still has the same quantity and magnitude of lightning within a 1-km buffer around that line. So, to go from ten momentary outages to about one per year is a remarkable improvement,” says Maddox. With that transmission line taken care of, GTC has now reached a point where its worst lines do not have more than three or four momentary outages per year. But, the company is still installing lightning arresters and otherwise improving its lines, where a majority of momentary outages are caused by lightning. In 2009, GTC had its best year ever for momentary outages: 0.951 momentary outages per consumer. In 2010, the lightning flash count for Georgia was up 20% over 2009. MAIFI was slightly worse (~7%) at 1.018 momentary outages, per consumer. Technology and a Change in Attitude GTC’s drive to improve MAIFI goes beyond just providing reliable service to its members, it is necessary to ensure the company’s future. “In the 1970s, a momentary outage simply meant that the lights blinked. Customers did not complain. Linemen would search for the cause of the problem, but, in general, everyone at the company was happy because the protection scheme worked properly (the breaker did not lock- out),” explains Maddox. “But, it is a very different world today. The digital age brought computers and, now, just about everyone has a dozen high-tech devices in their homes and offices. Momentary outages are a big problem,” continues Maddox. Also, for the last 15 years, Georgia has been experiencing an economic boom. High-tech companies are building new facilities and, invariably, these manufacturers—small and large commercial, industrial—are using computer controlled equipment. While it may be easy to put a UPS on a single computer, it is much harder to protect a conveyer line or an entire plant. For a manufacturing plant, a momentary outage can mean anywhere from two to four hours of downtime. Today, momentary outages negatively affect all of GTC’s members and if the company wants to provide comparable service to other utilities, it needs to get its momentary outages in-line with its peer utilities in the South. In Georgia, there is competition for new electrical loads. If a company is moving into the area, it will typically look at three to four sites. Invariably someone will ask, ‘If we build at Site X, in this industrial park, how reliable will our electric supply be?’ “To prosper, GTC must provide reliability for the digital age. Improving MAIFI is just one part of an ongoing effort,” says Maddox.

Worker installs a lightning arrester on a transmission line at GTC.

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