Experience with an improved stochastic method for diagnosing stator winding PD data

A pass/fail criterion developed to establish whether an insulation system is in good conditions or is affected by different types of PD phenomena, is discussed in this paper. It relies upon considerations which involve the quality of fit to the two-parameter Weibull function, the values of its parameters, as well as other average quantities. A set of rules are derived on these basis, which makes it possible to state the conditions of the insulation system. The failure of one or more of these rules provides an indication of PD phenomena, whose characteristics and harmfulness should be investigated. Results of application of the pass/fail criterion to AC rotating machine stator windings are reported and discussed