变压器油纸绝缘频域介电谱特性的仿真与实验研究

Simulation and Experimental Study on Frequency-domain Dielectric Spectroscopy of Oil-paper Insulation for Transformers

变压器油纸绝缘是一种复合电介质,油纸绝缘的老化会引起油纸绝缘体系介电特性的变化。为研究油纸绝缘频域介电谱特性参数与油纸绝缘复合电介质极化过程的关系,以及更好地将频域介电谱技术用于变压器老化状态无损诊断,通过变压器油纸绝缘扩展Debye等效电路模型仿真了绝缘电阻、几何电容以及时间常数分支电路参数的变化对油纸绝缘系统复电容频域介电谱的影响规律,通过频域介电谱实验研究了油纸绝缘系统的复相对介电常数、复电容、介损等参数与油纸绝缘状态和测试温度的关系,并根据电介质极化理论深入分析了油纸绝缘极化参数随频率和温度变化的规律。结果表明,频域介电谱法既可准确评估绝缘纸含水量和油纸绝缘试品老化程度,又能反映油纸绝缘试品的介电性能;用频域介电谱法评估油纸绝缘状态要保证测试温度的同一性。

The oil-paper insulation used in transformers is a kind of composite dielectric. The aging of oil-paper insulation will lead to the change of dielectric. To study the relationship between the parameters of frequency-domain dielectric spectroscopy （FDS） and the polarization process for oil-paper insulation, and better apply FDS in non-destructive diagnosis of transformer’s aging state, the affecting laws of insulation resistance, geometric capacitance and components of time-constant branch of circuit on the complex capacitance of oil-paper insulation were simulated firstly with the extended Debye equivalent circuit model. The relative permittivity, complex capacitance, dielectric loss and other parameters of the oil-paper insulation under different aging state and different test temperature were investigated by the FDS. The laws of polarization parameters of oil-paper insulation changing with frequency and temperature were analyzed on the basis of dielectric polarization theory. The results show that FDS can not only indicate the water content inside of insulating papers and the aging condition of oil-paper insulation accurately, but also reflect the dielectric property of oil-paper insulation simultaneously. The identity of the test temperature should be ensured to assess the condition of oil-paper insulation with FDS.