温度对变压器用油纸绝缘老化的频域介质响应的试验研究

变压器是电网安全运行中最关键的设备之一,由内绝缘(油纸绝缘)问题引发的变压器故障占变压器事故重要部分。目前用于诊断变压器油纸绝缘状态的方法尚存在各自的不足之处,故研究通过无损的诊断方法获取表征油纸绝缘老化状态的特征量,为评估变压器油纸绝缘老化状态提供准确且有价值的参考,无疑具有重要意义。基于频域介质响应的频域谱法是一种诊断电力变压器绝缘老化状态的非破坏性方法,笔者首先通过模拟变压器实际生产流程,制作变压器油纸绝缘试品,并对油纸绝缘试品进行加速热老化试验,得到不同老化程度的油纸绝缘试品。通过频域谱测试并分析了温度对油纸绝缘试品的频域介电特征量变化规律,运用电介质极化理论对测试结果进行了分析,为频域谱技术用于实际变压器油纸绝缘老化状态的无损诊断提供技术积累。结果表明:测量温度对频域谱诊断油纸绝缘老化状态影响显著,采用频温平移因子可以将任意测量温度下的频域谱曲线归算到同一参考温度,解决了测量温度对FDS测试结果的影响。初步研究结果表明,经过频温修正后的FDS能用于不同温度下的变压器油纸绝缘老化的评估。

Temperature Influence on Frequency Domain Dielectric Response to Transformer Oil-paper Insulation Aging

Transformer faults induced by oil-paper insulation defect account for a big part in total transformer accidents.However,the existing diagnostic methods of transformer oil-paper insulation are unsatisfactory.Therefore,it is necessary to develop a non-destructive detection method for obtaining a characteristic quantity which can characterize oil-paper insulation aging state and be taken as an accurate and valuable reference in the assessment of transformer oil-paper insulation aging state.In this study,the frequency domain spectroscopy(FDS)based on frequency domain dielectric response was adopted.An accelerated thermal aging test for oil-paper samples was conducted in laboratory,and the influences of temperature on the FDS parameters under different conditions of oil-paper insulation were obtained.The results show that: the measured temperature significantly affects the oil-paper insulation aging state diagnosed by FDS;the frequency-temperature shift factor can convert FDS curve at any measured temperature to the one at same reference temperature to eliminate the influence of measured temperature on the FDS results.Preliminary results indicate that the FDS modified by frequency and temperature can beused to assess transformer oil-paper insulation aging under different temperatures.