Investigations of transformer oil characteristics

In this paper, the behavior of various critical parameters of transformer oil is interpreted with a view to enhancing its life time. Systems abnormalities such as excess loading, switching, and ambient conditions are responsible for the accelerated aging and sudden failure of transformer. The level of insulation plays a significant role in the life expectancy of the transformer. The diagnostics of the critical parameters for the defined ranges of aging of transformer oil attempts to determine the level of insulation and serve to ensure its efficient operation. The approach includes formulation of suggestions for determining the insulation level of the power transformer. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

变压器油中溶解气体浓度的区间预测

应用灰色关联度分析方法确定了与待预测状态量关联度较高的因素,并利用熵理论建立了具有客观权重的组合预测模型。预测区间可有效量化由不确定因素引起的油中溶解气体浓度波动,应用比例系数法和粒子群优化算法建立了一定置信水平下油中溶解气体浓度的区间预测模型,且不受传统区间预测方法中必须服从正态分布的限制。实例结果验证了所提模型的有效性。     

Artificial neural network-based prediction technique for transformer oil breakdown voltage

This paper presents an artificial neural network (ANN)-based modeling technique for prediction of transformer oil breakdown voltage. This model comprises transformer oil service period, total acidity and water content while preserving the nonlinear relationship between their combinations for predicting transformer oil breakdown voltage. The model results are compared with those obtained by various modeling techniques such as ANN-based model for transformer oil breakdown voltage as a function of its service period, a polynomial regression model for transformer oil breakdown voltage as a function of its service period and a multiple linear regression model for transformer oil breakdown voltage as a function of its total acidity, water content and service period. A quantitative analysis of various modeling techniques has been carried out using different evaluation indices; namely, mean absolute percentage error and actual percentage error at each service period. The results showed the effectiveness and capability of the proposed ANN-based modeling technique to predict transformer oil breakdown voltage and justified its accuracy.     

变压器油中故障特征气体体积分数的预测

变压器是电力系统的重要设备,变压器油中溶解的故障特征气体体积分数是其进行绝缘故障诊断的重要依据。变压器油中气体体积分数的预测是周期性测试的重要补充。应用灰色多变量模型,对变压器油中溶解的5种主要特征气体,即氢气、甲烷、乙烷、乙烯和乙炔建立了MGM(1,5)模型,充分考虑了各种气体之间的相互影响,克服了常用预测方法在预测时只考虑某个特征参数或单独考虑几个特征参数发展变化的不足。通过预测实例分析,将MGM(1,5)模型的计算结果与相应GM(1,1)模型的计算结果比较,验证了该模型的准确性和有效性。     

运行中电力变压器油箱表面振动特性的研究

电力变压器油箱表面的振动信号与变压器绕组及铁心的压紧状况、位移及变形状态密切相关.因此,振动信号分析法是监测电力变压器绕组和铁心状况的有效方法之一.本文利用组建起的变压器振动测量系统,对现场正在运行中的电力变压器油箱表面的振动信号进行了测量,分析了变压器型号、传感器安装位置对所测得的振动信号的影响,结果表明:同型号变压器油箱表面的振动特性相似;油箱表面上下对称位置处的振动特性相差不大,而其它各个位置处的振动信号都没有可比性.最后,本文研究了传感器的安装位置略有变化时,所测得的振动信号的变化情况,提出了应对传感器安装位置进行标记,在进行下次测量时,传感器安装位置最好在标记点处或偏离不超过5 cm.本文的研究成果对于振动信号分析法的实际应用具有一定的指导意义.     

Flow electrification characteristics of transformer oil by rotatingelectrode systems

Flow electrification has been found to be the principal cause of a number of failures of forced oil cooled power transformers. Flow charging characteristics of oil/cellulose system with factors like electrode configuration, electrode material, presence of Benzotiriazole (BTA), metallic contaminants and copper coils were investigated for paraffinic oil by employing a rotating electrode system. A few hydrodynamic parameters (viz. Reynolds number, boundary layer thickness and friction factor) were correlated with flow charging characteristics of oil for varying temperatures concentrations of BTA. With concentrations of BTA in oil (viz. 10 ppm and 25 ppm) a marginal reduction in flow charging of oil was noticed, but about 40% reduction was observed with 150 ppm of BTA. A significant reduction in the flow charging characteristics of untreated and BTA treated oils was also observed in the presence of copper coils and metallic particle contaminants     

Artificial neural network and non-linear models for prediction of transformer oil residual operating time

This paper presents two modeling techniques for the prediction and monitoring of the characteristics of transformer oil. The first employs artificial neural network (ANN) and the second employs non-linear modeling (nlm). The proposed techniques are implemented for predicting the transformer oil residual operating time (t_rot) which is defined as the service period after which the breakdown voltage (BDV) violates the limits given in the standard specifications.The selection of the most influential characteristics on residual operating time (t_rot) in the proposed techniques is obtained by statistical analysis. The non-linear model depends on linear combination of non-linear functions for each characteristic. The ANN technique for modeling these characteristics preserves the non-linear relationship between these characteristics and (t_rot). The results are compared with previously published modeling techniques namely multiple linear regression and polynomial regression models. Different evaluation indices have been used to justify the superiority of the proposed modeling techniques for predicting (t_rot).     

极性反转电压下变压器油的击穿特性

为了获得换流变压器中变压器油在极性反转电压下的击穿特性,使用一种三电极模型,在不同间隙和温度下,对变压器油隙进行了极性反转电压击穿实验研究.击穿结果表明:极性反转电压下,变压器油的击穿场强没有随油间隙增加而降低;变压器油的击穿场强与温度相关,在实验温度范围内,40℃时出现了最大值.监测流过油隙的电流,发现在极性反转后电...     

基于随机森林的变压器油中溶解气体浓度预测

对油中溶解气体浓度进行分析及发展趋势预测,可以为变压器的状态评估提供重要的依据。传统的离线DGA方法因易导致延迟判断变压器的运行状态,造成一定的经济损失,现已不适用于油中溶解气体浓度分析及预测。因此,提出一种基于随机森林的变压器油中溶解气体浓度预测模型,以更准确地分析与预测油中溶解气体浓度。该模型以7种气体浓度构成特征向量空间,作为可视输入,并以目标气体浓度作为输出。试验结果表明,相较于传统的机器学习方法(BPNN、RBF和SVM),随机森林模型能更准确地预测油中溶解气体浓度,且需要调整参数少、训练效率高。通过算例分析,验证了该方法的有效性。     

油浸变压器用植物油

在ll篇文献的基础上,综述了变压器用绝缘植物油的研究现状,分析比较了植物油和矿物油的特性,指出了植物油绝缘的诸多优点和变压器用植物油存在的问题。得出植物油其生物降解率高,符合环保要求,具有良好的应用前景的结论。     

变压器油中局部放电信号超高频特性的研究

理论分析表明,局部放电信号所激发的电磁波具有很宽的频谱,它以TEM波的形式向外传播。本文通过实验模拟的方法研究了变压器油中的局部放电脉冲电流波形及所辐射的电磁波特性,实验结果表明,变压器油中的局部放电电流脉冲具有极块的上升沿,能激励起1．5GHz以上的超高频电磁波,它可以通过超高频传感器加以耦合接收,这就为进一步研究超高频检测技术在电力变压器中的应用提供了依据。     

Breakdown of transformer oil

Some of the factors affecting the dielectric strength of transformer oil are investigated. These factors include the stabilization phenomenon, oil and electrode pretreatment, the effect of oil velocity, the effect of a capacitance parallel to the test cell, and the effects of electrode area and gap spacing. The experimental apparatus and procedure are described, and the results are presented for each of the above factors. Suggestions for future research are offered     

变压器油性能检验的必要性

本文综述了变压器油的质量性能、技术要求和检验标准，并通过实例分析了变压器油的运行情况和变坏的原因，提出了应采取的预防措施。     

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.     

A newly modified forced oil cooling system and its impact on in-service transformer oil characteristics

This paper introduces a newly modified forced oil-cooling system, which comprises a bypass filter (BPF). The BPF has been introduced in such a way that its intake oil is the hot oil from the transformer top and to deliver it at the inlet of the oil-circulating pump. This system has been used for two transformers. Periodical measurements of the physical, chemical, and electrical transformer oil characteristics by standard testing methods before BPF operation, in operation and after stopping its operation in the transformer have been carried out. Before BPF operation, the results revealed that these characteristics are continuously deteriorating with the increase in transformer oil service period. However, when BPF is in operation, this deterioration not only has been reduced but also some of the characteristics have been improved. After the operation of BPF has been stopped, some of the characteristics resumed their deterioration. However, the rates by which these characteristics are deteriorating are noticeably smaller than their initial values. The deteriorated transformer oil characteristics (without installation of BPF) have been predicted by polynomial regression, multiple linear regression, and general linear multiple regression models. The efficiency and feasibility of the new cooling system in preserving in-service transformer oil characteristics have been proved and justified by quantitative evaluation of the measured and theoretically predicted deteriorated (without installation of BPF) characteristics.     

减小变压器油色谱分析误差的方法

油色谱分析法是判断变压器内部故障的主要方法之一,在变压器故障判断及处理过程中起着重要作用。可是由于种种原因．在实际操作中存在着各种误差。本文结合变压器油色谱分析的基本过程,从油样采集、脱气、标定和进样分析四个环节分析了变压器油色谱分析中误差的性质和原因;结合自己的工作经验,提出了减少变压器油色谱分析结果误差的方法。     

推挽变换器的变压器线圈损耗建模及其应用

由于四个线圈分时工作,应用于推挽变换器的变压器线圈交流损耗模型与线圈同时工作的高频功率变压器有很大不同.通过深入研究线圈电流谐渡磁势平衡特点,提出将一个四线圈分时工作的推挽变压器等效为两个独立的变压器,分别建立这两个变压器的谐波电流损耗模型,从而获得整个变压器的线圈损耗建模方法,并据此提出通过这两个等效变压器测量推挽变...