Practical Aspects of Apparent Charge Partial Discharge Measurements

While other industries have adopted charge measurement methods to monitor partial dis´charge severity, the power transformer industry has used RIV methods as the standard test. Very little practical comparative information has been published which relates these two methods. RIV meters can be used as charge indicators by making appropriate charge calibrations on the transformer under test. These procedures have been used to make parallel charge and RIV measurements on selected large power transformers. The results of these measurements show that there is no simple relationship between these two units of measurement. The actual relationship is a function of several transformer design parameters including physical size, type, and ratings. The results suggest that, for a given design type, RIV techniques may become less sensitive to partial discharge severity as transformer size increases. The results also show that RIV instruments can be used with charge calibration procedures to provide a more uniform measure of transformer quality.