染污绝缘表面受潮机理及其相角差检测原理研究

The detection of pollutions on insulator surface in natural environment is of significant importance for the anti-contamination work of power system. However, there are some deficiencies for the existing methods detecting pollution, for example, the ESDD (equivalent salt deposit density) method can't be intelligent, and the moisture absorption process of pollution is not be considered yet, and it is lack of standards research on test, and so on. Based on the thought of the partial surface conductivity, the DPA (difference of phase angle) will be studied and used for detecting the degree of moisture of pollution, and the relationship between electric parameter and pollution level under different degree of moisture of pollutions will be show by experimental study. Firstly, a quantitative measurement system for real-time electric parameters on polluted dielectric-surface will be designed and manufactured, in which the DPA between power voltage and sampling resistor voltage will be used. Then, the experimental study on the quantitative relation of the DPA and the moisture of pollution will be carried out in the artificial climate chamber, to simulate the process of natural moisture absorption. Thirdly, under different levels of moisture of pollution, the experimental research on the quantitative relation of leakage current, the surface conductivity and the pollution, for hydrophilic and hydrophobic polluted dielectric-surface, will be carried out systematically. Finally, the cluster analysis will be utilized to analyze a large number of measured results for a further research on values and time series relationship between the pollution level and electric parameters and the PDA. The research results will illustrate the moisture absorption process of pollution and the relationship among pollutions, electric parameters and environmental factors, and provide references for measurement technology of the pollution on insulator both at home and abroad.

自然环境下绝缘表面污秽检测对输变电设备外绝缘防污有重要的意义。污秽受潮机理及检测方法相关研究较少。本项目基于局部表面电导率法思想，研究污秽受潮的过程及其机理，采用相角差表征绝缘表面污层的受潮程度，并基于受潮程度测量研究局部表面电导率与污秽关系特性。首先，研究污秽受潮中冷凝、水滴碰撞、污秽吸湿能力和分子扩散的影响，建立相应物理模型；然后，设计并试制绝缘表面电导率等弱电参量测量系统，用电源弱电压和采样电阻电压的相角差检测污层受潮程度，避免局部放电发生；其次，模拟绝缘表面污秽自然受潮过程，实验研究相角差与受潮的定量关系；接着，实验研究染污绝缘表面电导率与污秽、受潮关系特性；最后，进一步研究污秽与电参量及相角差在数值和时间序列上的关系。本项目有助于理解绝缘表面受潮机理，获取电参量与污秽及其受潮程度三者关系。

污秽绝缘子的受潮状态对输电线路的外绝缘安全具有重要意义，本项目围绕染污绝缘表面受潮机理及其相角差检测原理开展研究。综合理论分析、电路仿真、数值模拟、试验研究和数据分析等，重点研究了绝缘子表面受潮程度检测方法与检测装置，相角差与受潮程度及闪络电压相关性，受潮影响因素及影响规律，受潮过程建模等。研究结果如下：.(1) 提出利用表面污秽两端电压与电流的相角差来表征污秽受潮程度的检测方法，该方法的理论测量误差低于0.1%，实测误差低于7%，并开发检测装置。对比研究了传统的电导率法检测受潮程度和相角差法，结果表明相角差法精度更高；.(2) 在蒸汽雾条件下，相角差值呈现先减小后增大的变化规律，受潮可分为1)起始受潮；2)快速受潮；3)饱和受潮；4)污秽流失四个阶段。相角差值与闪络电压值的相关系数接近于1；.(3) 研究蒸汽雾流量、污秽成分、污秽度及绝缘子材质、结构与型式对污秽绝缘子受潮特性的影响，建立了绝缘子表面污层电导率与环境温度、相对湿度、空气自由流速度、污秽度以及受潮时间之间的非线性函数模型。根据各因素的影响规律，提出了在不同环境条件下的绝缘子选型及其结构设计选择，为预防污闪提供参考。研究憎水性对受潮的影响，提出图像法识别憎水性，首次提出特征量的评价指标，分析了七种特征量对识别结果的影响，推荐其中五种组合为联合判据；.(4) 研究冷凝、水滴碰撞、污秽吸湿和分子扩散四种方式对受潮的影响，从热力学角度揭示了冷凝过程，研究了温度、温差和空气中水含量等对冷凝的影响；从流体力学角度模拟了水滴碰撞过程，发现了水滴直径和流速等对水滴碰撞的影响规律。建立了相应物理模型及经验公式模型，并以自制的相角差检测装置、水滴碰撞试验系统和受潮检测系统检验了理论模型，结果表明绝缘子积水率实测值与理论误差在10%以内。