The Research On AC Dielectric Properties Of Nonlinear Composite Insulating Dielectrics With Experiment

Nonlinear composite insulating dielectrics have been applied in generatorinsulation and cable termination insulation, consequently the study of thedielectric properties of nonlinear composite insulating dielectrics under AC fieldhave profound significance in engineering and theoretical study. This research isbased on nonlinear anti-corona tape and composite prepared using PE filled withnonlinear SiC so as to prove the influence factor and law of AC dielectricproperties of nonlinear composite insulating dielectrics experimentally.In this research, the comparison test of cured anti-corona tape and uncuredanti-corona tape was conducted firstly and the nonlinear degree of cured anti-corona tape was better than that of uncured anti-corona tape obviously; then ACdielectric property test was conducted to cured anti-corona tape and LDPE/SiCcomposite filled with SiC having different concentration under the sameconditions except for incentive voltage amplitude, temperature and frequency.The results indicate that the nonlinear degree of cured anti-corona tapedepends on the amplitude, frequency of incentive voltage, the higher theincentive voltage is, the clearer the nonlinear degree is, the property of nonlinearanti-corona tape doesn’t change significantly from ambient temperature to60℃,however, the higher the temperature is the clearer the nonlinear degree isform90℃to120℃, which means the ability of homogenization field and coronasuppression of nonlinear anti-corona tape is better at a high temperature than thatof at a low temperature.The difference with anti-corona tape is that the dielectric properties ofLDPE/SiC composite are also related to the concentration of inorganic filler,“dynamic negative conductivity” of LDPE/SiC composite prepared with lowconcentration was found for the first time using AC incentive voltage, which has nothing to do with the instantaneous value of electric field strength andfrequency but has something to do with the phase of AC incentive voltage andwhen the temperature rises the corresponding phase of “dynamic negativeconductivity” has decreased trend. The resistive current density of LDPE/SiCcomposite prepared with high concentration increases nonlinearly always as theelectric field strength rises. Through the study of the AC dielectric property andits factors of nonlinear composite, the polarization of nonlinear composite is thedouble-layered polarization between inorganic filler and polymer matrix onmicrocosmic surface and also is a typical which is inferred theoretically and alsois a slow polarization, which is inferred theoretically.