IR and Wetting Contamination

In an attempt to duplicate the findings at Ocean Road, an infrared inspection was performed on a 115/4.160KV transformer at one of our generating facilities. There are two station service transformers with a constant load of 7.5MW. During a period of light rain, one of the two transformers showed "hot spots" on the 115KV slant mounted bushings and corona activity could be heard. The transformer with the "hot spots" on the bushings is located closest to the salt water of the Piscataqua River, approximately 75 yards away in Portsmouth, New Hampshire. Minimal or no "hot spots" were noted on the sister transformer only 8 feet away and further from the river. We had not experienced any equipment failures due to salt spray contamination at this substation in the past. Upon further investigation, it was noted that these hot spots appear during periods of rain/snow. When the weather clears, the hot spots and corona dissipated. The Corona camera shows that arcing activity is present at the same location of the hot spot on the porcelain bushings.