冲击电压下电缆的介电响应特性与绝缘状态评估

Dielectric Response Characteristics and Insulation Condition Evaluation Under Impulse Voltage for Cables

针对传统频域介电谱法(frequency domain spectroscopy, FDS)在电缆绝缘测试中的不足,提出一种基于冲击电压下电缆介电响应特性评估电缆绝缘状态的新方法,并对其进行了理论和实验验证。通过分析冲击信号的频谱特征与绝缘介质的极化特性,论证了冲击介电谱法绝缘状态评估的可行性;利用电磁暂态程序(EMTP)仿真不同水树长度电缆的介电响应规律,从理论上验证了该方法的可行性;通过水树加速老化实验培养不同水树长度的短电缆试样,并搭建冲击实验平台进行实验测试。实验结果表明:利用介损-频率谱能够在1 000 Hz频率以下有效辨别出不同老化程度的短电缆样本,利用复电容虚部-频率谱能够有效判断出长电缆有无局部老化缺陷。研究结果表明,冲击下的介电响应特征能有效评估电缆的绝缘老化状态。

In accordance with the deficiency of conventional frequency domain spectroscopy(FDS),we proposed a new test method based on the impulse voltage response to evaluate the insulation condition of cables,and discussed the feasibility of impulse dielectric spectroscopy method by analyzing the frequency spectrum of impulse voltage and the polarization characteristics of dielectrics.Moreover,to investigate the dielectric response behaviors under impulse voltage,the cables with different aging conditions were simulated through an electromagnetic transient program(EMTP).Furthermore,the cables with different water-tree length were obtained by a water-tree accelerated experiment,and an impulse voltage platform was set up.According to the experimental results,the short cable sample of different aging time can be discriminated by dissipation factor-frequency spectroscopy under 1 000 Hz,and the partial aging defect in long cable can be diagnosed by imaginary capacitance-frequency spectroscopy.From these results,the dielectric response method under the impulse voltage can effectively discriminate the aging condition of the cables.