基于带电测试技术的变压器内部绝缘子缺陷检测方法研究

Study on live-line testing technique-based method for detecting defect of transformer internal insulator

由于水电站变压器内部绝缘子缺陷情况复杂,现有检测方法评价指标较为单一,无法准确检测变压器内部绝缘子缺陷情况。为解决该问题,提出新的基于带电测试技术的变压器内部绝缘子缺陷检测方法。获取变压器内部绝缘子缺陷的发热与温升关系,利用环境温度与运行负载参量的顶层油温对电力变压器绕组热点温度进行计算,设计绝缘子缺陷检测试验,测试变压器内部绝缘子在测量距离不同时的电场强度,分析变压器内部绝缘子导通性缺陷的影响。结果表明:测量距离20 cm时得到的分布曲线接近U型分布,并且较为光滑;在裂缝距离接近于0时,电场强度出现最大峰值;理论结果与实际结果拟合度在90%~100%之间。绝缘子的测量距离不同电场强度也不同,且绝缘子伞裙芯棒片数越多,电场强度越弱。实际结果对比拟合度较高,说明基于带电测试技术的水电站变压器内部绝缘子缺陷检测结果可靠性强。该方法能准确检测出绝缘子缺陷,且操作简单,具有良好的应用前景。

Due to the complexities of the defects of the internal insulator of transformer in hydropower station, the evaluation indexes for the existing detecting methods are relatively simple and then cannot correctly detect the defects of the transformer internal insulator. In order to solve this problem, a new live-line testing technique-based method for detecting the defect of transformer internal insulator is proposed herein. With this method, the relationship between the heating and temperature rise of the internal insulator defect of the transformer is obtained, the hot spot temperature of the winding of the power transformer is calculated with the temperature of the environment and the top oil temperature of the operating load parameters, and then an insulator defect detection test is designed for testing the electric field strengths of the internal insulator of the transformer with different measuring distances, while the influence from the conductivity defect of the transformer internal insulator is analyzed as well. The results show that the distribution curve obtained at the distance of 20 cm is close to the U-shaped distribution and is relatively smooth,while the electric field intensity reaches the maximum peak value when the fracture distance is close to 0, for which the fitting degrees between the theoretical results and the actual results are between 90% and 100%. The electric field strengths are different for different measuring distance of insulator, while the more the number of the core rods of insulator shed is, the weaker the electric field strength is to be. The fitting degree for the comparison with the actual measuring result is higher, thus it is indicated that the reliability of the detecting result of the defect of the internal insulator of transformer in hydropower station made by the live-line testing technique-based method is strong. This method can correctly detect the insulator defect through a simple operation, and has a better application prospect.