Exprimental Research On Space Charge Of Linear/Non-linear Two-layer Composites

With the development of power electronics, the direct current(DC)transmission technologies gradually mature and have been widely used in powersystem. For DC plastic cable as critical equipment in DC transmission, how tosolve the space charge accumulation in the bulk of its insulation materialsdetermines whether it is successfully applied to high voltage/ultrahigh voltageDC transmission. When plastics are used as DC cable insulation materials, theirinternal physical defects under electric field are apt to accumulate the spacecharge, leading to the non-uniform internal electric field, affecting the dielectricstrength of cable and accelerating the cable insulation aging. In recent years, thespace charge suppression for polymer insulation materials has been concerned athome and abroad.The paper is based on nonlinear insulating dielectrics, adding a layer ofnonlinear insulating dielectric as barrier layer between polymer as maininsulation material and semi-conductive shield. First, nonlinear barrier layerswere prepared with low density polyethylene(LDPE) as matrix and SiliconCarbide(SiC) and Zinc Oxide(ZnO) inorganic nanoparticles as independent filler,respectively. Then, two-layer composite samples were made with the nonlinearbarrier layer and single-layer LDPE. Space charge distributions of the compositesamples were obtained from pulsed electro-acoustic(PEA) method. The resultsintend to reveal the space charge suppression of nonlinear barrier layer to maininsulation material. Moreover, the signal recovery software for the space chargedistributions of single-layer plate samples were developed to solve the spacecharge measurement of two-layer plate samples, which provided theoreticalanalysis basis on the space charge suppression of nonlinear barrier layer to themain insulation material.