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Technologies
used by HV Diagnostics
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Partial
Discharge (PD)
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| Partial
discharges are the very fast movements of
small amounts of charge within localised
parts of the dielectric of a piece of
high voltage equipment.
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| Partial
discharge activity is normally sporadic
unlike corona activity which is more
consistent. PD activity will typically occur
above a voltage (called the inception
voltage) and will disappear below another
voltage (extinguishing voltage). These
voltage levels are not necessarily equal but
their relative magnitudes compared to the
operating voltage as well as each other are
important.
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| Partial
discharge activity would typically indicate
potential for failure of the equipment at
the point of the partial discharge. Of
interest to the tester is the magnitude of
the PD, the frequency of the PD and the
position of the PD. Cable joints are
normally associated with significant PD
activity.
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| Partial
discharge equipment is typically operated in
very noisy environments where nearby
electromagnetic activity is easily measured
by the sensitive pd detectors designed to
detect the small PD currents. A number of
techniques have been developed to filter the
extraneous noise from the partial
discharges.
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