On site very high frequency P.D. pulse measurements on full size rotating machine stator for discharge type recognition

The work described in this paper follows the study of the ageing kinetics of the insulating material submitted to P.D. in a test cell. The dependence of the natural frequencies of P.D. pulses on insulation age was found. Thus, a qualitative as well as quantitative new P.D. measuring apparatus could be developed for the monitoring of high-voltage rotating machine ageing. The P.D. measurements presented in this paper are part of the feasibility study of this new measuring device. Several measurements on real H.V. motors were needed to confirm the feasibility of a very high frequency P.D. pulse measuring device and recognition method. Very high frequency P.D. pulse measurements were performed on site on high voltage motor insulations, using the same type of instruments than those used previously in the laboratory on a motorette. The results published here show that, in full size insulations, the different types of P.D. pulses significant in different periods of ageing of the voids can be recognised by their frequency components. These results confirm the design of the P.D. measuring device built by SITELEC