Abstract: This paper presents results from tests on eight stators as well as a laboratory model on the characteristics of partial discharge (PD) pulses detected by resistance temperature detectors (RTDs). It is clear from these experiments that the RTD leads – rather than the RTD element itself, primarily detects the PD signals. In addition, if the RTD lead is shielded, the detected signal is extremely small. Thus PD measurements should only be attempted with unshielded RTD leads. Unfortunately whether leads are shielded or unshielded is often unknown. The data also shows that even with unshielded RTD leads, the detected signals are usually uncorrelated with the PD measurement using conventional sensors, and thus the known condition of the stator winding. Although RTD leads may detect PD, interpretation of the results cannot be based on magnitude, polarity or phase position. Thus interpretation is extremely subjective – even by an experienced expert.
