超低频激励下变压器油纸绝缘的载流子浓差极化研究

Study on Concentration Polarization of Oil-paper Insulation in Transformer Under Ultra-low-frequency Excitation

PDC和FDS法的超低频响应对油纸绝缘受潮、老化的诊断具有较好效果,研究表明,油纸绝缘电介质的超低频响应具有明显的弥散现象,针对超低频响应的机理,目前尚未统一定论;文中通过分析载流子在不同频率下迁移速度不同造成的浓差极化,推导超低频激励下油纸绝缘中的内部极化电流函数,并结合载流子移动的统计特性,构建超低频下的介电响应模型,用以解释油纸绝缘电介质响应的低频弥散现象。与实测PDC数据比较认为模型符合实际情况,表明具有统计性的载流子浓差极化可以认为是造成油纸绝缘低频弥散的主要机制。

Ultra-low-frequency response of FDS and PDC method is useful for diagnosing moisture or ageing of oil- paper insulation, and studies have shown that dispersion exists in dielectric response curves under ultra-low- frequency excitation. But there is not yet unified conclusion about the mechanism of low-frequency response. In this paper, by analyzing concentration polarization caused by carrier migration, function of polarization current under ultra-low frequency excitation is derived. Then the stochastic statistical model of carrier mobility inducing low frequency dispersion is established to explain low-frequency dispersion. By comparing with the experimental PDC data, it is found that the model conforms to the actual situation, show that： the low-frequency dispersion of oil-paper insulation are mainly caused by statistical concentration polarization.