부산대학교 도서관

In the HVDC project, the insulating material of the dry-type bushing of the converter transformer mainly uses epoxy impregnated paper. Surface charge will accumulate on the surface of the capacitor packet easily under the operating DC electric field. The surface charge will distort the electric field on the surface of the insulating material and it will be a threat to insulation safety. In order to study the surface charge accumulation characteristics of epoxy impregnated paper materials under DC electric field, we conduct surface charge measurement experiments on cylindrical samples of epoxy-impregnated paper with or without two-component polyester coating at room temperature. Its surface charge accumulation properties were obtained by measuring its surface charge characteristics after applying voltage for different time. The result shows that coated samples only accumulate charges of the same polarity as the applied voltage, and surface charge polarity of uncoated sample is as same as the polarity of its high and low voltage electrodes. Coated samples reach stabilization more quickly (The charge density gap rapidly narrows in the measurement result of 1, 3, 5 and 10h), uncoated samples are slower to reach stabilization. The average value of the charge density of the painted sample after taking the absolute value is 3.74 times higher than that of the unpainted sample after applying +26kV voltage at room temperature for 10h, and the average value of the charge density of the painted sample after taking the absolute value is 11.8 times higher than that of the unpainted sample after applying −26kV voltage at room temperature for 10h. For the sample of the same kind, the charge density of the coated sample under negative polarity is higher than that under its positive polarity, the charge density of the coated sample under negative polarity is lower than that under its positive polarity. For uncoated samples, the surface charge distribution is related to the distribution of the adhesive layer and paper layer on the surface, and the charge distribution of the coated sample is relatively even. For analyzing the effect of epoxy impregnated paper coating and optimizing the electric field on the surface of the material, obtaining this charge distribution law has important meaning in engineering.