Substation Insulator Failure Prevention by Ultrasonic Corona Detection

Ultrasonic detection of electrical corona discharge has become an important and useful tool for the detection of faulty insulators. The ultrasonic test unit consists of a hand-held probe-microphone responsive to acoustic energy in the 36-to 44-kHz range and is battery powered. Solid-state electronics translate high-frequency sonics to the audible range and provide amplification through a speaker or headset. The characteristics associated with a phenomenon are preserved through translation. Energy released at 40 kHz by corona or arcing is recognizable as the familiar ``frying´´ sound. Similarly, air pressure leaks emit ``hissing´´ sounds at 40 kHz. Application of this principal has resulted in the replacement of numerous insulators before occurrence of serious electrical failures. Minute inspections and tests revealed porcelain cracks and mechanical imperfections that would have eventually resulted in critical electrical faults. Similarly, leaks have been eliminated in compressed air systems, thereby reducing compressor service demands.