Non-destructive measurement of the degradation of transformer insulating paper

Knowledge of the condition of power transformer winding insulation paper is fundamental to making optimum asset replacement decisions in the power industry. The ability to assess the aged condition of Kraft paper quickly and non-destructively using portable instrumentation would significantly increase the opportunities for gaining this knowledge. Insulation paper degrades over time in-service and its degree of polymerization (DP) reduces, eventually affecting its mechanical strength. At low DP levels the insulation may start to disintegrate and the risk of electrical breakdown increases. Currently-used methods of estimating DP are either approximate or destructive. The use of spectroscopy together with multivariate statistical analysis (MVSA) provides a powerful non-destructive evaluation of the condition of paper. From initial feasibility studies, we have developed a simple, portable system (TRANSPEC) using fiber-optics and broad-band spectroscopy that can measure the degree of polymerization of various aged transformer papers to a precision of approximately 30 DP units with a spatial resolution of 14 mm. The system can also measure the chemical composition and condition of the insulating mineral oil. MVSA regression models were constructed from library spectral data, and these models are used to predict the DP of other papers with parameters that fall within the range spanned by the set of calibration samples. Separating oil and moisture information from wetted paper is possible and will be reported in a separate publication. With a single TRANSPEC system, non-destructive in-situ analysis of the DP of insulating paper is possible, providing a rapid cost-effective method for transformer insulation condition assessment and monitoring, which correlates well with current destructive methods.     

绝缘油色谱分析在变压器故障查找中的应用

绝缘油气相色谱技术是检测变压器潜伏性故障的有效手段,文章通过2个实例,介绍了绝缘油气相色谱技术在2台静电除尘器变压器故障分析中的应用。     

油／气绝缘套管出线变压器现场试验方法

通过油／气套管和GIS连接的电力变压器是一种新型结构电力设备。对其进行介质损耗和电容测量试验,需要将SF6气室打开才能进行试验接线,现场处理难度大,并且容易在处理过程引起新的设备缺陷。文中介绍不打开SF6气室,对变压器进行介质损耗和电容测量的试验方法。理论分析和现场试验证明,该试验方法简单,测试数据可靠。     

金属钝化剂BTA对变压器硫腐蚀的抑制效果及绝缘油性能的影响研究

油中的腐蚀性硫化物会侵蚀变压器绝缘绕组,导致油纸绝缘性能下降,给变压器的运行带来安全隐患,工程上常通过加入金属钝化剂来抑制腐蚀性硫化物与铜离子的结合,进而延缓硫腐蚀过程的发生。研究了油中常用金属钝化剂苯并三氮唑(BTA)对铜硫化物形成的抑制效果,并研究了钝化剂在长期运行过程中对变压器绝缘油性能的影响。结果表明,在含有腐蚀性硫的绝缘油中加入BTA可以有效缓解变压器硫腐蚀,但高浓度的BTA会促使油中铜离子含量增加,而油中铜离子能通过传递分解过氧化氢产生过氧化自由基,加速油品劣化,导致油纸绝缘老化加速。     

变压器匝间绝缘故障的分析

介绍了变压器匝间绝缘故障的起因和特点。阐述了诊断变压器匝间绝缘故障常用的绝缘油色谱分析和高压试验数据相结合的分析方法。结合实碌工作经验,提出了分析变压器匝间绝缘故障几点意见。     

变压器油中糠醛含量测试与分析

变压器油中糠醛浓度是绝缘纸老化程度的重要指标。介绍了液相色谱对绝缘油糠醛分析方法的依据，并建立了分析方法。通过数据表明测试糠醛的必要性。     

变压器油抗氧化性能的热分析评价

通过差示扫描量热技术(DSC)，测定变压器油氧化放热峰的起始温度，并考察加入不同质量分数的抗氧剂(T501)后，它对变压器油氧化起始温度及抗氧化性能的影响最后的实验结果证明，差示扫描量热技术是一种快速评价变压器油抗氧化性能有效的新方法。     

Mechanism of increase of electrostatic charging tendency in insulating oil for oil‐immersed transformer

The mechanism of the increase in the electrostatic charging tendency (ECT) of insulating oil and causative compounds were investigated by accelerated deterioration tests with the addition of various compounds. Although the ECT of the insulating oil was almost constant when only sulfoxide compounds were added, a marked increase was observed when either hydrochloric acid or moisture, which was considered to be generated by the aging of insulating oil, was also added to oil containing sulfoxide compounds. It is assumed that the sulfonium ion, which is generated by the reaction between sulfoxide compounds and hydrogen ion, is the compound that directly contributes to the increase in the ECT. Hydrogen ions can be supplied from organic acids generated by the oxidation of hydrocarbons in aging insulating oil. It is considered that the increase in the ECT of insulating oil is caused by the generation of sulfoxides by the oxidation of sulfide, which are present in fresh oil (originating compounds), and the generation of sulfonium ions by a reaction between sulfoxide and hydrogen ions, which are formed during aging. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(4): 26–33, 2011; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.21113     

采用改进Davidson-Cole介电模型的变压器油纸绝缘状态分析

为利用频域介电谱准确分析变压器油纸绝缘状态,引入考虑直流电导率与跳跃电导率的改进DavidsonCole介电模型。运用测量的频域介电谱数据参数化改进Davidson-Cole介电模型,将其转化为非线性优化问题。选用混合蛙跳优化算法对改进Davidson-Cole介电模型参数进行辨识,得到了弛豫时间τ、圆弧不对称度β和直流电导率σ_(dc)等特征参数。研究了老化与受潮对油纸绝缘试样的改进Davidson-Cole模型参数的影响特性,结果表明β与糠醛含量、σ_(dc)与水分含量有着良好的指数关系;τ与糠醛含量、水分含量有着良好的对数关系。通过线性拟合获得了糠醛含量、水分含量与模型参数的量化关系式,其拟合优度较高,因此可利用改进Davidson-Cole模型定量评估变压器油纸绝缘状态。     

变压器套管油位雾霾图像检测方法

针对雾霾天气下的视频图像测量,传统的颜色空间转换方法会由于图像对比度降低而失效。在图像预处理阶段,暗通道先验去雾算法被广泛运用,但是这种算法的计算效率不高,用于变压器油位测量中不能达到实时要求,因此,为了快速测量油位,提出了一种基于暗通道优先和颜色空间变换的油位测量方法。在去雾阶段,对每个像素点的透射率进行逐个估计得到粗透射图,再对其进行修正,从而得到去雾图像。去雾之后,采用加权分布的自适应增强算法对图像进行增强。在油位测量阶段,在HSV空间取阈值分离出目标区域。实验结果表明,测量油位误差在±1%的同时,相比传统算法提高了近5倍效率。在保证良好效果时,能减少算法的时间复杂度,使变压器油位测量算法在雾霾天气下也能有效。     

变压器油色谱分析诊断技术

为了监测变压器运行状况,提出了对变压器采用气相色谱分析诊断技术和三比值法,介绍了它们的特点,论述了变压器油色谱分析在变压器潜伏性故障诊断上的应用效果,总结了变压器油色谱分析诊断技术在实际应用中需要注意事项.     

Mineral insulating oil in transformers

Nearly all load bearing transformers in electric power delivery systems around the world are filled with liquid. The liquid functions both as an electrical insulation and as a heat transfer fluid. The liquid in almost all of these units is transformer oil, petroleum-based insulating oil refined specifically to meet the requirements of this application. Transformers in electric power distribution and transmission systems are expected to function reliably and efficiently and to do this for many years. The quality of the oil in a transformer plays an important role in performing this function, and the characteristics of transformer oil have been examined and reported on for decades. This article discusses some of these characteristics and the relationships between these characteristics and the production and in-service performance of mineral transformer oil. Transformer oil is used around the world, but the emphasis here is on practices in the United States     

变压器绝缘电阻试验中容易忽视的几个问题

介绍了绝缘电阻受温度及外界电磁场干扰等因素的影响 ,提出了解决办法 ,避免一些错误判断给生产运行带来影响     

变压器油中气体含量异常问题的技术分析

通过对1台SFPSZ9/150000/220电力变压器油中气相色谱跟踪测试,结合高压电气试验,经综合分析查出了变压器油中气体含量异常的原因,并准确判断出故障部位.     

电力变压器油纸绝缘系统气隙特征分析

针对电力变压器油纸绝缘系统由于自身老化产气、换油处理不当等引入气隙(空穴)的影响绝缘性能研究方法的不足,引入回复电压法有效诊断油纸绝缘状态来判断气隙状况。在理解介质响应理论基础上,建立了油纸绝缘模拟实验,统计分析并拟合了测量数据,研究了不同充电时间下绝缘系统中气隙含量的变化对回复电压特征参数的影响规律。结果表明:回复电压最大值随绝缘系统中气隙含量的增加呈二次线性规律增大,而中心时间常数随绝缘系统中气隙含量的增加呈二次线性规律减小,初始斜率随着绝缘系统中气隙含量增加呈三次线性规律增大,最后对多台实际变压器进行测试分析,验证了回复电压法可对油纸绝缘系统中气泡情况有效诊断的结论。     

绝缘纸中空间电荷效应的模拟研究

为明晰空间电荷对油纸绝缘纸板中电场强度的畸变效应、纸板老化状态与空间电荷的作用机制,采用双极性载流子输运模型,对不同老化状态的绝缘纸板中的空间电荷特性进行数值模拟。对于同一老化状态下的绝缘纸板施加直流电压时,纸板中会出现同极性电荷积聚现象,且正极性电荷的分布范围较负极性显著变窄;随着加压时间的增加,纸板中的电场畸变率呈增大趋势。当绝缘纸板老化程度加深时,其陷阱密度和深度均会增加,致使空间电荷在纸板的近电极侧大量积聚,进而削弱纸板和电极边界处的电场强度,加剧纸板内部的场强畸变;且绝缘纸板老化愈严重,空间电荷对电场的畸变作用愈突出,使得绝缘纸板加速老化,容易诱发绝缘击穿故障。研究结果可为变压器油纸绝缘设计提供参考。     

油纸绝缘变压器介质响应模型参数辨识研究

以扩展徳拜介质响应等值模型为出发点,获得可辨识等值电路的数学模型,对如何准确辨识模型参数展开研究,首次在变压器介质响应模型参数辨识中引入分层思路,并提出分层-压缩因子法,实现基于回复电压现场测试数据的等值模型参数辨识。通过对结果对比分析得出,该算法具有使用灵活、精确高效等特点;本文分别对两台实际变压器进行建模研究,结果表明,该优化算法所辨识的等值模型能有效反映两变压器实际情况,为进一步分析变压器绝缘状态与回复电压特征量之间的关系打下基础。     

在线色谱在电力变压器油分析中的应用分析

本文介绍色谱在线监测技术的基本原理和关键组成,通过实例对色谱在线监测和实验室离线分析进行数据比对。数据表明,在线监测技术可以反映变压器运行状态和故障发展的趋势。