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Selasa, 18 Mei 2010

ULTRASONIC ELECTRICAL INSPECTION

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DESCRIPTION

When electrical apparatus such as switchgear, transformers, insulators or disconnects and splices fail, the results can be catastrophic. This is just as true in industrial plants as it is in the power transmission and distribution side. Electrical discharges such as arcing, tracking or corona are all potential for equipment failure. In addition, the problems of RFI and TVI impact on our valuable communication networks. If left undetected, these conditions can become a source of an arc flash incident, which can result in severe injury or death. Arcing, tracking and corona produce ultrasound and are detected with an Ultraprobe.

How Ultrasonic Electrical Detection Works

Arcing, tracking and corona all produce some form of ionization which disturbs the air molecules around it. The Ultraprobe detects the high frequency noise produced by this effect and translates it, via heterodyning, down into the audible ranges. The specific sound quality of each type of emission is heard in headphones while the intensity of the signal is observed on a meter. Normally, electrical equipment should be silent, although some may produce a constant 60 cycle hum or some steady mechanical noises. These should not be confused with the erratic, sizzling frying, uneven and popping sound of an electrical discharge.

Detection Method

Before beginning any inspection of mid or high voltage equipment, be sure to review your plant or company's safety procedures. Essentially, as in generic leak detection, the area of inspection is scanned starting at a high sensitivity level. To determine the location of the emission, reduce the sensitivity and follow the sound to the loudest point. If it is not possible to remove covers, or plates, scan around the seams and vent slots. Any potentially damaging discharges should be detected.
When it is not possible to get close to the test equipment, such as for safety reasons or while inspecting over-head power lines, use a parabolic microphone. UE Systems has two models, the Ultrasonic Waveform Concentrator (UWC) and the Long Range Module (LRM). These highly sensitive, directional sensors double the detection distance of a standard scanning module and provide pinpoint accuracy.
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