Dielectrometry measurements of moisture dynamics in oil-impregnatedpressboard

In oil-impregnated pressboard of medium and low humidity the complex dielectric spectrum's shape and amplitude do not change with variations in temperature and moisture content, but only shift in frequency. Thus it is possible to create a `universal' curve, with appropriate temperature correction factors, which can be used to extract information about the moisture dynamics of solid transformer insulation from dielectrometry measurements. To create the universal curve, measurements are taken with the material placed in a parallel-plate structure whose complex impedance is measured. To measure spatial distributions of dielectric properties, imposed ω-k (frequency-wavenumber) dielectrometry is used, where a set of interdigitated electrodes on one surface of the material cause the electric field to have a limited depth of penetration into the dielectric, proportional to the electrode spacing. Measurements using the parallel-plate methodology establish a mapping of the dielectric spectrum of EHV-Weidmann HIVAL pressboard impregnated with Shell Diala A transformer oil, as a function of temperature and water content. This mapping is then used to determine spatial moisture profiles in pressboard in other experiments which make use of a three-wavelength interdigitated sensor     

基于最小二乘法的变压器油中微水含量在线监测方法

变压器油中微水含量是1个非常重要的技术参数,为了更加准确地监测油中微水含量的真实情况,分析了电力变压器油中水分的存在形态及其危害,以及油温对油中水分溶解度的影响,采用了以相对饱和度和温度为监测特征量对变压器油中的微水含量进行在线监测。同时针对变压器油中微水含量在线监测的技术要求,采用卡尔.费休滴定法确定某一油样的微水含量,以及应用传感器检测到的油样温度与相对饱和度,提出了基于最小二乘法的变压器油中微水含量监测方法,从而实现油中实际微水含量的在线监测,保证了在线监测变压器油中微水含量的准确性。     

国产克拉玛依超高压变压器油替代进口Diala油可行性研究

按照ASTM和DIN等国际标准或等同于这些国际标准的国家标准试验方法,对我国克拉玛依系列5种型号超高压变压器油和进口壳牌公司Diala变压器油的各项性能指标进行试验、分析和比较,为南方电网超高压输电公司今后在进口直流换流变压器使用国产变压器油提供重要的理论依据和技术支持。研究结果表明：国产克拉玛依K150AX、K150GX超高压变压器油在综合性能方面比进口壳牌Diala油优越,因此可以替代进口壳牌Diala油在高压直流换流变压器上使用。     

变压器油中微水含量在线监测的研究

分析了变压器中水分的分布状况以及油中水分的变化情况,提出了以相对饱和度和温度为监测特征量的变压器油中微水含量在线监测的方案。采用聚酰亚胺电容式湿度传感器和温度传感器实现对油中微水含量的在线监测,并利用计算机完成数据的采集与分析。在试验变压器上进行的实验表明传感器工作正常,能很好地反映变压器油中微水含量,达到在线监测的目的。     

变压器油中水分在线监测的神经网络计算模型

为了对变压器油中的微水含量进行在线监测和建模计算,介绍了变压器油纸绝缘中水分的分布和利用聚酰亚胺薄膜电容式湿度传感器在线监测变压器油中微水含量的原理并在变压器油中微水含量监测的相关理论基础上,提出了一种基于神经网络的在线监测计算模型以评估变压器油中的微水含量。比较油中微水含量的计算值与测量值证明,采用该模型能够发现变压器中导致油中水分异常变化的故障。实际测试结果表明该模型能很好地反映变压器油中水分的实际情况。     

变压器油中微水含量的实时测量

论述了变压器油中微水含量监测的现状及发展状况,采用一种聚酰亚胺电容式传感器对变压器油中微水实时测量进行了研究.     

Application of common transformers faults diagnosis methods on biodegradable oil-filled transformers

Due to environmental concerns regarding the use of mineral oil, biodegradable oil is increasingly being used as an alternative dielectric fluid. This paper presents results of experiments performed in the laboratory on the use of biodegradable oils for transformer application. The investigations cover two important diagnostic techniques for insulation assessment: (i) an investigation of partial discharge (PD) activity and characteristics in such oils and (ii) an investigation of the standard hydrocarbon dissolved gas products produced due to transformer faults. The fundamental aim of the investigation was to provide information as to whether the existing analysis techniques of PD fault pattern recognition and dissolved gas analysis methods, developed for mineral oil, are valid when used for insulation assessment with biodegradable transformer oil. The experiments were conducted on test samples to simulate three common types of transformer faults: low-energy PDs, high-energy arcing/sparking, and overheating. For the purpose of comparison, the same tests were performed using a mineral oil (Shell Diala MX) and a biodegradable oil (Envirotemp FR3). Also, each oil type was tested at three different moisture levels and with or without the presence of solid insulating materials (pressboard). PD activity was monitored using the standard IEC60270 phase-resolved analysis method. The fault gases produced were extracted and analysed by standard gas chromatography methods. Test results indicate that the PD phase resolved patterns are, in general, similar for the two oil types and thus existing PD pattern interpretations can be used to distinguish different types of PD faults, e.g. corona versus surface discharges. However, the values of various discharge quantities (PD magnitudes, repetition rate, current, etc) are very different under the same test condition. The quantities and the trend of dissolved gases for faults in biodegradable oil are substantially different compared with mineral oil. For the PD fault, biodegradable oil was found to release only a limited number of gases. For arcing and overheating faults, the main key gas produced is different between the two oils. Also, the presence of cellulosic materials such as pressboard influences the extent of hydrocarbon gases dissolved in the oil. It was found that for biodegradable oil, fewer amounts of gases are produced as the oil gets wetter.     

一种基于水活性的油中微量水分测量方法

工业生产中使用的矿物质油的品质和性能与油中的微量水分含量密切相关。过量的水汽污染会导致油品降解、加剧设备的腐蚀和磨损。因此水分是工业油品常规检测项目之一,无论是使用前还是使用过程中,对油品中水分含量进行精确在线监测都显得尤为重要。根据相平衡热力学的有关原理,类比食品中水活性的定义,推导出了油中水活性的定义,建立了水活性和相对湿度之间的联系,将水活性的测量转换为相对湿度的测量。并引用饱和裕度的概念说明了用水活性表征微水含量的科学性和合理性。提出一种基于水活性的油中微量水分的测量方法。测量结果表明该测量方法具有较好的测量精度,能有效地描述油中微量水分的变化情况。     

基于CAV424的变压器油微水检测

近年来,变压器监测系统的研究受到广泛的关注.其中绝缘油中的微水含量是主要的检测对象,其对变压器油的绝缘性能及机械强度有很大的影响.本文对几种油品微水含量的检测方法进行了简要讨论,分析了变介电常数式电容传感器的测量原理.针对变压器油微水含量检测引入新型的高精度电容/电压信号转换集成芯片CAV424.同时较为详细地阐述了其基本原理并对其实际应用电路进行了设计.实验结果表明,CAV424能够获得可靠的性能和精度,并具有较高的应用价值.     

Moisture determination of the main insulation in a transformer by frequency‐domain spectroscopy

The presence of moisture in the oil–paper insulation in a transformer drastically accelerates the aging process of the insulation and reduces the service life of the transformer. To analyse the influence of moisture on the dielectric response of the oil–paper insulation and to precisely determine the moisture content of the transformer by frequency‐domain spectroscopy, the modified Cole–Cole model is introduced to fit the frequency versus dielectric responses of the oil–paper insulation samples with different moisture contents, and the influence of the variation in moisture content on the parameters in the modified Cole–Cole model is investigated. Results show that the modified Cole–Cole model parameters, including the α and β relaxation components as well as the DC and hopping conductivity components, can be used to effectively fit the frequency versus dielectric response curve of the oil–paper insulation. The characteristic parameters τ_α and τ_β in this model are found to be sensitive to changes in the moisture content. They can be used to quantitatively evaluate the moisture content in a transformer insulation system. A case study is presented to verify the effectiveness of the proposed technique in assessing the moisture content of onsite transformers. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

镍掺杂碳纳米管传感器检测变压器油中溶解气体的气敏性

检测变压器油中溶解气体的成分和含量对变压器运行状态的诊断和评估有重要意义。提出一种用镍掺杂的碳纳米管气敏传感器检测变压器油中溶解气体的方法,介绍其制备方法、试验方法及步骤,并对变压器油中气体进行气敏响应测试以及气敏响应机制的探讨。试验结果表明:与混酸修饰的碳纳米管相比,镍掺杂碳纳米管对变压器油中溶解的6种组分气体有更高的灵敏度和响应速度;对低浓度(1～10μL/L)的C2H2气体,传感器的电阻变化率ρ与气体浓度满足一定的线性关系。证明了所研制的传感器具有检测低浓度气体的能力,能够体现变压器油中溶解气体的大致产生情况及近似浓度。     

变压器油微水在线监测技术原理及实现

论述了变压器油微水在线监测原理、检测方法和系统技术的实现,实现了微水信息的在线采集和处理。     

基于介电响应的油纸绝缘寿命预测方法

油纸绝缘是油浸式电力变压器的重要组成部分,其绝缘寿命受热老化因素影响很大.因此,针对不同温度、不同含水率下的油浸纸板的寿命预测问题进行分析,提出一种应用平移因子和纤维素反应二阶动力学方程预测不同温度、不同含水率下的油浸纸板寿命的方法.首先,针对不同含水率的油浸纸板进行变温介电谱测试和130℃条件下的加速老化试验;其次,...     

电压响应方法在电力变压器状态评估中的应用

Power transformer is one of the most important equipment in the power system.Its operating condition affects the reliability of power supply directly.Therefore,in order to guarantee transformer operation safely and reliably,it is necessary to assess condition of power transformer accurately.Return voltage method based on voltage response measurements is still a new non-intrusive diagnosis method for internal insulation aging of transformer.In this paper the technique and application of return voltage measurement and some results of voltage response measurements of several transformers was introduced.Voltage response measurements were performed on various transformers with different voltage grades,various operating periods,different moisture contents and aging degrees on site.Derived moisture contents from return voltage measurement were compared with the corresponding moisture contents obtained from the analysis of oil samples.Based on on-site experiments and theoretical analysis,the criteria for insulation state of transformer are proposed.Moisture condition of transformer insulation can be determined by using return dominant time constant,and a good correlation between aging degree and the return voltage initial slopes of the aged transformers.Field test performed on several transformers,its interpretation of results are also presented,which proves that return voltage measurements can be used as a reliable tool for evaluating moisture content in transformer insulation.     

水分对油纸绝缘热老化速率及热老化特征参量的影响

本文设计了在110℃和130℃下初始含水量分别为1%、3%、5%的绝缘纸试品在变压器油中的老化试验。系统地研究了不同初始含水量对油纸绝缘热老化速率的影响,分析对比了老化过程中的绝缘纸聚合度、纸中含水量、油中含水量、油中糠醛含量、油中酸值等老化特征参量的变化趋势。研究结果表明:初始含水量从1%增长到3%的绝缘纸平均降解速率的增长率比初始含水量从3%增长到5%时大得多,且从3%增长到5%时降解速率的增长率已经很小,有趋于饱和的趋势;老化过程中油中水分与纸中水分均是波动的,二者的波动幅度有较好的正相关关系,且二者整体上波动趋势的关系与初始含水量有关;水分含量及其变化趋势能影响老化过程中糠醛、酸等老化特征产物的变化趋势。因此本文提出应根据整个老化过程中油、纸二者水分含量整体上波动趋势的关系及波动幅度的大小来对变压器油纸绝缘进行状态评估及受潮分析,并建议在根据传统的油中糠醛、酸值等老化特征参量来对油纸绝缘进行状态评估及故障诊断时需充分考虑水分的影响。     

Drying of transformer insulation using zeolite

Power and distribution transformers are some of the most important components in the power network. The presence of moisture in a transformer deteriorates the transformer insulation by decreasing both the electrical and mechanical strength of the solid insulation. It is of great importance to pay attention to the moisture content of composite insulation systems in order to maintain low dielectric loss, high dielectric breakdown strength and low rates of degradation of the insulating system in HV equipment. In this paper, an approach to the said problem is presented. With the application of a synthetic hygroscopic mineral (molecular sieve zeolites) - a revolutionary, environment friendly, multipurpose mineral - a continuous drying process of the transformer oil during operation without the need for service interruption is achieved. A study of the effects of zeolite on the electrical and dielectric behaviour of the insulating liquid of the transformer is included in this paper.     

一种SF6气体微水含量在线监测装置

文章简述了SF6气体绝缘设备水分的来源及危害;介绍了有关部门对SF6气体水分含量的限定指标及常用的SF6气体水分含量测量方法;阐述了以高分子薄膜电容式湿度传感器作为相对湿度(RH)的在线监测元件的工作原理;指出对SF6气体绝缘开关微水含量进行在线监测,不仅能对运行中高压开关的绝缘气体实行有效控制,同时也能为状态检修提供有利依据。     

运行变压器油防劣化措施的实际应用

阐述了变压器油劣化的危害以及油劣化的原因,结合电厂的实际情况,针对促使变压器油劣化的因素,提出了严格控制变压器油的运行温度、水分含量和介质损耗因数,将开放式油枕改造为胶囊式油枕,根据变压器油指标的变化情况及时进行净化处理等行之有效的防劣化措施,保证了变压器油的良好性能和设备的安全稳定运行。     

Optimisation of a sensor for onsite detection of partial discharges in power transformers by the UHF method

Among the different solutions which allow onsite Partial Discharge measurement in energized power transformers, the UHF technique is gaining general interest. In order to apply this method in existing transformers, it is considered advantageous to design a UHF sensor to be fitted inside the transformer tank. This paper describes the constraints affecting the development of such sensor and the process followed to optimize its design. During this process, different solutions for broadband UHF antennas were analysed. The selection was based on computer simulation and experimental results. Computer simulation was used to evaluate differences in radiation pattern, antenna impedance, gain and effective area. Measurements of the antenna response to different partial discharge sources in oil were performed using an oil dielectric breakdown test set in an electromagnetic shielded laboratory. A group of selected antennas were then tested in a power transformer simulating the broadband signals generated by partial discharges by injecting controlled voltage pulses in the transformer. Finally, a sensor based on a conical monopole antenna structure was built and attached to a specially designed housing to be fitted inside the transformer tank through the drain valve. This final prototype was benchmarked during a high voltage factory test of a power transformer which showed a significant partial discharge activity.