Hm. Li et al., TRANSIENT CURRENT MEASUREMENT FOR THE DETECTION OF WATER TREE GROWTH IN POLYMERIC POWER-CABLES, IEEE transactions on dielectrics and electrical insulation, 2(5), 1995, pp. 866-874
In this paper, the relationship between the frequency and time domain
windows is discussed. From this study an appropriate time window for t
ransient current measurements may be chosen so that reliable low frequ
ency dielectric data can be obtained. The suitability of applying eith
er Fourier transform or the Hamon approximation for the derivation of
low frequency responses is discussed for transient currents with diffe
rent shapes. With water-treed LDPE samples aged in the laboratory, mea
surements of transient currents, with subsequent transformation into t
he frequency domain, show a loss peak at similar to 10(-4) to 10(-3) H
a when moisture is retained in the samples. Even with free water remov
ed, a higher dielectric loss is observed in water treed samples compar
ed to virgin samples. The relaxation behavior may serve as an indicato
r of water treeing in polymeric cable insulation. The results of both
transient measurements and TSDC results can be affected significantly
by the treatment conditions of the samples. The application of vacuum
to a water treed sample can alter the activation energy of the conduct
ion process and the TSDC spectra.