The Experimental Study On AC Dielectric Properties Of Electric-stress Grading Tape

Electric-stress grading tape is a nonlinear composite insulating dielectricwhich can homogenize electric field distribution automatically and suppresscorona in a non-uniform electric field, researching AC dielectric properties ofelectric-stress grading tape have profound significance in engineering andtheoretical study. Electric-stress grading tape is researched to prove the influencefactor and law of AC dielectric properties of nonlinear electric-stress gradingtape under the three-electrode flat and two-electrode blade.In the measurement of the AC dielectric properties of electric-stress gradingtape, the time domain wave forms of incentive voltage and responding currentcan be measured, so in order to obtain the basic characteristic curves of thenonlinear electric-stress grading tape, this paper presents a decomposing method,named as” frequency domain decomposition method”, the decomposition methoddecomposes the responding current waveform into the resistive current andcapacitive current waveforms referencing the incentive voltage wave. It can beproved that the decomposition method can realize the current decomposition forthe measurement in which the standard sine wave incentive voltage whose initialphase is zero is applied through simulating and measured data validation.This paper used the AC test system based on differential method, testelectrode were three-electrode flat and two-electrode blade, then AC dielectricproperty test was conducted to cured electric-stress grading tape having differentconcentration under the same conditions except for incentive voltage amplitude,temperature and frequency.The results indicate that the dielectric properties of nonlinear electric-stressgrading tape depend on the amplitude, frequency of incentive voltage andtemperature. Using three-electrode flat test system, the adjustment ability ofelectric-stress grading tape for non-uniform electric field is stronger with the higher incentive voltage amplitude; when frequency is less than100Hz, theadjustment ability of electric-stress grading tape for electric field decreases withthe increase of frequency, when frequency is more than100Hz, the adjustmentability of electric-stress grading tape for electric field increases with the increaseof frequency; when temperature is less than60℃, the adjustment ability ofelectric-stress grading tape for electric field increases with the increase oftemperature, when temperature is more than60℃, the adjustment ability ofelectric-stress grading tape for electric field decreases with the increase oftemperature. Using two-electrode blade test system, the adjustment ability ofelectric-stress grading tape for electric field increases with the higher incentivevoltage amplitude; with the increase of the frequency of incentive voltageamplitude, dielectric parameter of electric-stress grading tape the adjustment ratechange greatly as well as its adjustment ability for electric field. With theincrease of temperature, conductance adjustment rate of electric-stress gradingtape becomes smaller as well as static capacitor adjustment rate but dynamiccapacitor adjustment rate becomes larger.