气固复合绝缘变压器聚酯材料老化特性研究

Aging characteristics of polyester material of gas-solid composite insulated transformer

为了研究长时间运行下SF6气固复合绝缘变压器的老化状态,建立了变压器内部聚酯绝缘材料老化评估模型。首先对6020型PET薄膜进行加速热老化实验,然后采用频域介电谱、差示扫描量热、拉伸以及近红外光谱检测PET材料的老化特性。实验发现,PET薄膜介电损耗随老化呈现先减小后增大趋势,采用Havriliak-Negami介电弛豫模型处理后选取了典型特征参量τ1和τ2,并拟合得到了老化时间与τ1和τ2的经验公式;PET薄膜的结晶度和断裂伸长率随着老化呈现先增大后减小趋势,拉伸强度呈现减小趋势;PET薄膜近红外吸光度随着老化呈现减小趋势,采用线性判别分析算法进行降维处理后获得了较好的分类结果。综合分析可得,频域介电谱弛豫时间常数τ1和τ2、拉伸强度和近红外光谱吸光度特征参量可以较好的表征聚酯材料的老化程度。

In order to study the aging state of SF6gas-solid composite insulated transformer under long-term operation, an aging evaluation model of polyester insulation material inside the transformer was established. Firstly, the accelerated thermal aging experiment of 6020 PET films was carried out, and then the aging characteristics of PET materials were detected by frequency domain dielectric spectroscopy, differential scanning calorimetry, tensile and near infrared spectroscopy. The experimental results show that the dielectric loss of PET films decreases first and then increases with aging. The typical characteristic parameters τ1and τ2were selected by using the Havriliak-Negami dielectric relaxation model, and the empirical formulas of aging time and τ1and τ2are obtained. The crystallinity and elongation at break of PET films firstly increase and then decrease with aging, while the tensile strength decreases. The near infrared absorbance of PET films decreases with aging, and the linear discriminant analysis algorithm was used to reduce the dimension of PET films, and good classification results were obtained. The results show that the dielectric relaxation time constants τ1and τ2, the tensile strength and the absorbance characteristic parameters of near infrared spectrum can better characterize the aging degree of polyester materials.