Technology Trends: High-speed imaging examines insulator electrical discharges

To efficiently distribute electricity to factories and homes over long distances, power stations use transformers to step up voltages to around 450,000 V.

Dec 1st, 1999
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To efficiently distribute electricity to factories and homes over long distances, power stations use transformers to step up voltages to around 450,000 V. Such high voltages require special precautions to protect power-transmission and distribution equipment and ensure personnel safety.

An important safety component of high-voltage transmission lines is the glazed ceramic insulator. These insulators are shaped to present a long tracking path that helps prevent electrical breakdown to the support gantry or Earth. When these insulators do break down, electrical discharges with velocities in excess of 100 km/s can be created.

To gain a better understanding of why electrical discharges on such high-voltage insulators occur, ABB Corporate Research (Vasteras, Sweden) and DRS Hadland (Tring, England) jointly produced a special version of DRS's Imacon 468 high-speed imaging system, which provides the necessary ultraviolet (UV) sensitivity and temporal resolution to record unpredictable electrical breakdown phenomena.

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PHOTO. DRS Hadland Imacon 468 imaging system can image the high-voltage electrical breakdown discharges of ceramic insulator materials at 100 million frames/s.

To provide the necessary discharge data, a redesigned stand-by mode allows the Imacon 468 system to be updated at 100 million frames/s without the need for a predefined data-collection start trigger. And, by integrating a high-gain amplifier into the Imacon 468 system, the designers enhanced its UV sensitivity, which allows the imaging of weak emissions from pre-breakdown electrical streamers.

According to ABB, previous attempts to record these events have failed to reconstruct an accurate representation of the processes involved because these imaging systems used single-frame cameras to produce a montage of images from a series of experiments.

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