Abstract
We have constructed a prototype of partial discharge (PD) pulse measurement and degradation diagnosis expert system (PDM/ES-I) using a personal computer for insulation degradation diagnosis of materials suffering from PDs. For 0.1 mm-thick low density polyethylene (LDPE) with CIGRE Method II electrode system, temporal change of phase-angle-resolved PD pulse occurrence distribution was measured with PDM/ES- I. We applied the so-called "pattern recognition" of the PD pulse distribution to diagnosis of insulation degradation and assessment of residual life. Experimental results revealed that in spite of large scattering of time to breakdown, i. e. life, from 5 to 43 hours, all the tested samples exhibited similar evolution of the profile of PD pulse occurrence distribution with increasing aging time. The PD pattern measured at a given aging time was compared with five standard normalized PD patterns which had been registered in advance as five representative degradation stages from initial degradation category to final one. The degradation stage determined by the pattern recognition (PR) method proved to vary from the initial degradation category to final one in a correct turn. Consequently, the PR method permitted an exact determination of the degree of degradation at a given aging time. In other words, the PR method was capable of predicting the residual life of LDPE with a CM-II electrode system.
