电工技术学报  2024, Vol. 39 Issue (11): 3444-3456    DOI: 10.19595/j.cnki.1000-6753.tces.230513
高电压与放电 |
基于介质响应电流频变特性的油纸绝缘受潮状态评估方法
夏源1, 杨丽君1, 吕晓露2, 汪可2, 李金忠2
1.输变电装备技术全国重点实验室(重庆大学) 重庆 400044;
2.中国电力科学研究院有限公司 北京 100192
Evaluation Method of Oil-Paper Insulation Damp State Based on the Frequency-Dependent Characteristics of Dielectric Response Current
Xia Yuan1, Yang Lijun1, Lü Xiaolu2, Wang Ke2, Li Jinzhong2
1. State Key Laboratory of Power Transmission Equipment Technology Chongqing University Chongqing 400044 China;
2. China Electric Power Research Institute Beijing 100192 China
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摘要 油纸绝缘受潮状态的准确评估对于电力设备安全稳定运行至关重要,该文研究并提出了一种以介质响应电流幅值Im随激励电压频率f变化为特征的油纸绝缘受潮评估新方法。试验测试了不同水分含量油纸绝缘样品在频率f为0.01~50 Hz正弦激励电压下的f-Im特性,并对Im按照其最小值进行归一化处理得到f-I*曲线。结果表明:在双对数坐标下,随着受潮程度增加油纸绝缘的f-I*曲线会由干燥时的一条直线逐渐变为一条下凹的曲线。进一步提出将50 Hz处的I*I*@50Hz作为特征参量,用于量化油纸绝缘水分含量,并在实验室模型和实际油浸式设备上验证了该方法的有效性。与传统利用频域介电谱诊断油纸绝缘受潮的方法相比,该文所提特征参量与水分含量的量化关系受绝缘结构差异和油纸绝缘聚合度变化的影响较小,在设备绝缘结构和老化状态信息缺失的情况下具有更好的普适性。另外,该方法所需测试时间仅约100 s,具有高效、准确和便捷的特点。
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关键词 油纸绝缘频率响应电流水分含量    
Abstract:Moisture in the oil-paper insulation is an important cause of performance degradation in power transformers, and accurate assessment of the moisture state of the insulation inside the equipments is important to ensure its safe operation. At present, the method of projecting the moisture content of insulating paper according to the moisture content in oil has led to great errors in field application due to the complicated influencing factors. In recent years, the insulation condition diagnosis technology based on dielectric response test method has received wide attention, and some characteristic parameters and evaluation methods have been proposed, but the accuracy of the evaluation results is greatly influenced by the differences in transformer insulation structures and cannot yet meet the needs of practical engineering applications. Based on the previous research results, this paper further explores the influence of moisture on the response current characteristics of oil-paper insulation, and aims to propose an efficient evaluation and diagnosis method of insulation moisture state that is less affected by the difference of insulation structure and easy to implement in the field.
First, oil-paper insulation samples with different moisture contents and different polymerization degrees were prepared. In order to measure the response current signals of the oil-paper insulation under voltage excitation of different frequencies and amplitudes, a response current test system for oil-paper insulation was built. The response currents of the samples were tested in the frequency range of 0.01 Hz to 50 Hz. The response current amplitude at 0.01 Hz was used as the reference value, and the response current amplitude at different frequencies was normalized to obtain the f-I* curve. The f-I* curve of oil-paper insulation will change from a straight line when dry to a concave curve as the moisture content in the paper increases, while the f-I* curves of oil-paper insulation with different polymerization degrees basically overlap. When the moisture content is low, the f-I* curve basically does not change with the voltage amplitude, but when the moisture content is large the voltage increase will cause the right side of the f-I* curve to shift down slightly. Oil-paper composite insulation systems with different structures were made using circular cardboard and ring cardboard, and the test results showed that the FDS method is significantly affected by the insulation structure, while the difference in insulation structure has minimal effect on the f-I* curve when the moisture content in the insulation paper is the same. Finally, I*@50Hz (i.e., the I* value at 50 Hz) was proposed as a characteristic parameter to quantify the moisture content of the transformer oil-paper insulation, and a fitting equation between it and the moisture content of oil-paper insulation was established. For oil-impregnated insulated cardboard with different times of natural moisture absorption, the absolute error between the evaluation results and the actual measurement results of the Karl Fischer instrument was less than 0.09%. For actual oil-paper insulated bushings and transformers, the evaluation results were reasonable and consistent with the overall pattern of the results obtained by commercial insulation diagnostic analyzers.
The following conclusions can be drawn from the experimental results: (1) The f-I* curve is closely related to the damp state of the oil-paper insulation. When the oil-paper insulation is dry, its f-I* curve is a straight line. However, the rise law of the f-I* curve in the low-frequency band will significantly change after the insulation is damp, and the whole curve will turn into a concave curve. (2) The test results of the f-I* curves are basically not affected by the insulation structure and insulation aging. This mechanism has more advantages compared with the FDS test method, which is greatly affected by the insulation structure. (3) This study proposed to take I*@50Hz, wherein the I* value at 50 Hz in the f-I* curve is used as the characteristic parameter to evaluate the dampness of the oil-paper insulation, and the test time is only approximately 100 s. The effectiveness of this method to evaluate the moisture content of oil-immersed equipment is verified by testing the actual oil-paper insulation bushings and transformers.
Key wordsOil-paper insulation    frequency    response current    moisture content   
收稿日期: 2023-04-22     
PACS: TM855  
基金资助:国家电网公司总部科技项目资助(5200-202155590A-0-5-GC)
通讯作者: 杨丽君 女,1980年生,教授,博士生导师,研究方向为高压设备绝缘状态和故障诊断的在线监测,以及电力变压器和电缆的老化机理和诊断等。E-mail:yljcqu@cqu.edu.cn   
作者简介: 夏 源 男,1997年生,硕士研究生,研究方向电气设备在线检测与绝缘故障诊断。E-mail:xiayuan@cqu.edu.cn
引用本文:   
夏源, 杨丽君, 吕晓露, 汪可, 李金忠. 基于介质响应电流频变特性的油纸绝缘受潮状态评估方法[J]. 电工技术学报, 2024, 39(11): 3444-3456. Xia Yuan, Yang Lijun, Lü Xiaolu, Wang Ke, Li Jinzhong. Evaluation Method of Oil-Paper Insulation Damp State Based on the Frequency-Dependent Characteristics of Dielectric Response Current. Transactions of China Electrotechnical Society, 2024, 39(11): 3444-3456.
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