采用频域介电谱法的高压干式套管屏间局部绝缘劣化诊断

Resin impregnated paper (RIP) bushing is an important component of transformer, and its failure caused by local inter-foil insulation deterioration may result in phase-to-ground fault or high energy explosion, seriously threatening safe operation of substation. To carry out further study of the phenomena of local inter-foil insulation deterioration of RIP bushing, a multilayer model of epoxy impregnated paper samples is established with different parallel resistors for indicating severity of insulation deterioration. Then a diagnosis method based on frequency-domain dielectric spectroscopy (FDS) is proposed and investigated under room temperature. Results indicate that, with deterioration of local inter-foil insulation, its C-f and tanδ-f curves have obvious transition process. In early stage of local insulation deterioration, detection method of power frequency is less effective. However, validity of FDS method shows better result. In addition, CIGRE bushing model is modified for rapid descending section of high frequency band of tanδ-f curve. The calculated results with the modified model are in good agreement with experimental results.