A Study On Interface Polarization Properties Of EP/ZnO Double Layer Composite Insulation

The suppression problem of space charge is the key to make polymerdielectric successfully used in high voltage and ultra-high voltage DC powercables. In order to solve this problem, besides adding inorganic fillers in the maininsulation to modify the main insulation, a new method has been come up withwhich is to add a nonlinear insulation dielectric barrier layer between thesemi-conductive shielding layer and the polymer main insulation is used asbarrier layer to restrain the space charge. Regulating Micro interface properties ofnonlinear dielectric barrier layer which can be used to control the insulationproperties of composite material, but the relationship between micro interfaceand dielectric properties cannot be verified directly, therefore the micro interfacein the linear/nonlinear composite materials could be imitated throughconstructing linear/nonlinear double-layer insulation macro interface structure.The main purpose of this paper is to study polarization properties of themacro interface between Zinc Oxide valve plate and epoxy resin of thelinear/nonlinear double-layer insulation and lay a foundation on the space chargesuppression mechanism on nonlinear barrier layer through the test method ofpolarization and depolarization current time-domain spectroscopy (PDC).Experimental results show that the PDC of double-layer insulation differsfrom single medium obviously because of different dielectric property with eachlayer; meanwhile, the interfacial charge polarity of the double-layer compositeinsulation depends on the polarity of test voltage, so the corresponding PDC isalso different. The double-layer dielectric interface charge polarity which is inaccord with voltage polarity in the side of ZnO, and the polarization anddepolarization charge accumulation and dissipation of double-layer sample withdifferent contact surface paste measurement and different polarity of test voltageare not identical, which can be showed by the theory of the interfacial net chargeQ(t). The reason why the measured polarization properties of double-layer composite sample differences under different voltage polarity is that ZnOconnected to the measuring electrode will accumulate the most charge appliedpositive voltage. Research shows that different thickness ratio of EP/ZnO samplehas impact on polarization, the thicker the ZnO layer is, the inferior thepolarization will be. EP/ZnO double-layer dielectric polarization absorptioncharge amplitude grows with the increasing applied electric field and thetemperature.