On-line partial discharge calibration and monitoring for power transformers

Partial discharge (PD) is one of the major factors causing insulation damage of power transformers. This paper describes the development of on-line partial discharge monitoring system for transformers. The developed set can monitor up to four power transformers continuously. It uses various methods to reject interference and enhances monitoring sensitivity of PD effectively. The optical cable is applied to communicate between measurement system near transformers and the upper computer in the main control building. On-line calibration of partial discharge quantity is requisite for on-line detection or monitoring. This paper describes an on-line calibration method using pulse injection through tap of high voltage transformer bushings. It also discusses the influence of limit inductance and bushing capacitance, from tap of bushing to ground, in on-line calibration circuits. Influences of multi-grounding of the transformer tank for monitoring and calibration are also discussed. Simulation in laboratory and site test shows that the method is practically valid for on-line PD calibration of power transformers within permissible engineering error range under certain defined conditions. This system has been in operation steadily in 500 kV substations for more than 2 years.     

一种容性电力设备的保护和监测新方案

套管事故是变压器事故的常见类型,因此有效地监测套管事故并及时地切除变压器以防止事故的进一步扩展显得十分重要。介绍一种用于套管、电流互感器等容性电力设备的监测保护新方案。该方案在容性套管末屏接地引下线上串联一个供测量用的电容器和电流互感器,监测这个串联电容器两端的电压信号和串联电流互感器的电流信号,从而发现容性电力设备的电容层击穿程度以实现对设备的保护。新方案具有可实现对监测装置本身的循环自检的优点。     

基于LSTM的箱式变压器高压套管温度预测

针对箱式变压器环境封闭、散热性能差而导致变压器各部件温度较高,且变压器套管事故率高的现状,提出一种基于长短期记忆(Long Short-Term Memory, LSTM)神经网络的箱式变压器高压套管温度预测方法,对箱式变压器高压套管热流进行分析,建立基于LSTM的变压器高压套管温度预测模型,LSTM算法可以解决有效解决变压器高压套管温度预测所存在的非线性和时滞性的问题,通过红外传感技术对某小区箱式变压器高压套管相关数据进行在线监测,对现场数据进行预处理,通过算例分析验证了文中所提方法预测精度更高、误差更小、泛化能力更强。对比结果表明,所提方法优于普通循环神经网络(Recurrent Neural Network, RNN)和支持向量机(Support Vector Machine, SVM)预测方法,平均误差分别降低了27.4%和36.3%,预测精度更高,与变压器套管温度实测值更趋一致。     

A diagnostic method based on RVM (return voltage measurement) for condenser bushings with oil–paper insulation systems

The bushing of a transformer is one part of the transformer system, but is as vital as the transformer itself because it forms a part of the main circuit. Deterioration and abnormal condition of the bushing possibly cause its destruction, shortage of the main circuit to the Earth, and fire in the systems, so that diagnosis of the bushings is thus very important. At present, mainly visual inspection from outside of the bushing is carried out. Inspection of the inside condition of the bushing by dissolved gas analysis of the inside oil is done only as sampling for selected bushings because it is difficult due to the sealed construction of the bushings. Therefore, a simple diagnostic method for bushings has been expected for a long time. In Eastern Europe, the RVM (Return Voltage Measurement) method based on scanning the polarization spectra was applied to the oil–paper insulation systems inside the transformer as a diagnostic method. In this paper we investigate theoretically the principle of the RVM method applied to bushings with the same oil–paper insulation systems as the transformer by using the equivalent circuit, and the possibility of using this novel diagnostic method for condenser‐type bushings is demonstrated by a model experiment. © 1999 Scripta Technica, Electr Eng Jpn, 130(1): 21–29, 2000     

不拆引线测量500 kV自耦变压器套管电容量及介质损耗的方法

500 kV自耦变压器体积庞大,套管高,拆除引线和接测量线都有困难。然而,自耦变压器高压套管、中压套管及中性点套管实为同一绕组连接,在低压绕组首尾短接接地的前提下,从中性点加测量电压、从套管末屏取试品电流来测量高压及中压套管电容量及介质损耗,可避免拆装引线和在高、中压套管上接拆测量线。通过对500 kV自耦变压器进行模型简化和等效电路运算,得出从中性点加测量电压测高压套管电容量及介质损耗的误差;并对广东省中山市500 kV香山变电站2台自耦变压器现场实测,验证了此种方法的可行性。     

基于多源融合的油纸绝缘套管缺陷辨识及绝缘状态评估

油浸纸绝缘套管作为变压器的关键组件,其绝缘受损会威胁变压器主设备的运行安全。针对此现状,提出一种基于多源融合的油纸绝缘套管缺陷辨识及绝缘状态评估方法。首先,根据实际运行工况制备典型缺陷试验套管,并开展频域介电响应、局部放电及红外热成像联合试验,辨识套管缺陷种类。然后,提取套管绝缘指标量,引入隶属度函数及状态得分算子,建立基于博弈论组合赋权法的套管绝缘状态评估模型。最后,分别采用组合赋权法和单一赋权法的评估模型,对正常以及缺陷套管进行算例分析。结果表明：联合试验可以准确辨识套管缺陷种类。组合赋权法弥补了单一赋权法评估结果片面的不足,且正常套管的模型评估分数均高于缺陷套管。评估结果与套管实际绝缘状态一致,验证了套管绝缘状态评估模型的正确性及有效性。     

Apparatus for Online Power Transformer Winding Monitoring Using Bushing Tap Injection

Online transformer condition monitoring techniques based on transfer function methods, such as transmission-line diagnostics and swept frequency-response analysis, require the injection of a known test signal into the transformer. On larger power transformers, a practical method is to use the available bushing tap connection. In this paper, we will discuss a custom high-power signal generator that injects high-frequency signals on the bushing tap of the transformer under investigation, as well as a circuit to replace the bushing tap short and allow online operation of the system. Finally, the system is demonstrated on a 650 kV transformer.      

±800 kV 云广特高压换流变压器现场安装关键技术

以±800 kV云广特高压直流输电工程穗东换流站高端换流变压器现场安装调试为基础,介绍了高端换流变在现场安装调试过程中应注意的关键技术环节。穗东换流站800 kV高端换流变压器的现场安装施工难度高于常规换流变压器,主要体现在安装环境洁净度控制、阀侧套管出线装置及套管安装、散热器安装、真空处理和热油循环、牵引就位等方面。     

变压器高压油浸纸套管与环氧浸纸套管运行情况比较

对某电厂使用的变压器高压油浸纸电容式套管和环氧浸纸电容式套管的运行情况进行了比较,并对曾出现的故障类型进行了分析.历次电气试验表明:油浸纸电容式套管介质损耗和电容量均保持稳定,变化量一直在规程允许范围内;而环氧浸纸电容式套管在投运一定时期后,出现套管介质损耗因数及电容值增大的现象.最后指出,环氧浸纸绝缘套管的介质损耗因数普遍高于同等电压等级的油浸纸绝缘套管,当发现绝缘介质损耗因数和电容值发生较明显变化时,应加大测试密度,当变化量大于10%时,必须更换套管.     

On-line diagnostics of high-voltage bushings and currenttransformers using the sum current method

Experience with the application of the sum current method to on-line diagnostics of high-voltage bushings and current transformers is presented. The method and analysis are described along with field experience obtained at fourteen substations, comprising 56 sets of (three) bushings and current transformers. The influences of temperature, humidity and changes in more than one bushing are discussed     

特高压变压器现场安装关键技术及应用

在特高压晋东南变电站1号主变的现场安装过程中,施工单位进行了大量的安装技术研究工作：结合变压器的结构特点优化了现场安装流程;改进了高压出线装置和高压套管的安装方法;给出了合理选择性能满足特高压绝缘油指标要求的油务处理设备的方法;深入研究了大体积油箱的抽真空处理、热油循环等器身干燥技术以及低温环境下根据施工阶段低温气候特点现场处理油务的内容。文中的研究可为实现特高压变压器现场安装的技术攻关和质量创优提供参考。     

通过750kV变压器套管末屏进行过电压监测的方法研究

针对西北750kV超高压电网所处特殊自然环境下易遭受过电压危害的特点,研究探索750kV电网过电压监测方法。根据变压器电容式套管结构原理,研制出系列750kV变压器套管末屏连接专用精密低压臂分压器,与套管电容组成测量过电压信号的冲击电压分压系统。分析研究了750kV变压器套管末屏频率响应特性,该系统可满足电网雷电冲击、操作冲击过电压现场测量的要求。论证了750kV电网采用变压器电容式套管末屏连接低压臂分压器进行过电压监测的可行性。     

On Seismic Response of Substation Equipment and Application of Base Isolation to Transformers

This paper presents seismic performance of electric substation transformers, and discusses advantages and considerations in the use of base isolation as a viable hazard mitigation option. Substation transformers and bushings are the most critical elements within the power delivery system and their performances during past earthquakes in the U.S. and abroad have not been satisfactory. Finite-element analyses indicate that the interaction between these two critical elements has a significant effect on seismic vulnerability of substations. In light of dynamic characteristics of this equipment, base isolation can be very effective in mitigating this adverse interaction. Furthermore, due to high-inertia reduction, base isolation can also have beneficial effects on the long-term longevity of transformers and on foundation performance during seismic events. Larger displacement demand and uplift, however, are issues that must be considered in the application of base isolation. Through an actual case study (433.3-MVA transformer in a high-voltage substation), a simplified model of the transformer bushing will be developed and the results of fixed base case and base isolated case are compared. Moreover, design concepts will be investigated that will demonstrate larger displacement can be accommodated; and that considering transformer geometry, peak ground acceleration, amount of inertia reduction, and isolator's friction coefficient for this transformer uplift is not an issue.     

一起由于套管密封失效导致的220kV变压器故障分析

油浸电容式高压套管在大型变压器上应用十分广泛,承担了载流、绝缘、密封等多项功能。针对一起频繁地震后发生的220 kV变压器匝间短路故障进行了试验检测、解体检查、套管结构分析等,结果表明,故障原因为套管密封结构不合理,在特殊工况下使密封失效。     

500kV息烽变过电压在线监测装置的研究与应用

介绍了一种利用变压器电容式套管,安装特制的电压传感器组成套管分压系统,从电容式套管的末屏抽头处获取电压信号的方法,实现对电网过电压信号的实时采集。介绍了装置的总体组成结构及各部分的工作原理,详细论述了套管末屏电压传感器的结构设计。     

云广±800kV直流输电工程换流变压器现场安装关键技术

基于云广±800kV直流输电工程穗东换流站高端换流变压器现场安装试验,包括阀侧升高座出线装置安装、阀侧套管安装、散热器安装和换流变压器油处理等,对±800kV直流换流变压器现场安装环境条件、安装的关键技术及其与常规换流变压器安装的差异等进行了探讨。     

换流变压器网侧套管绝缘在线监测系统研究

针对高压直流输电系统中换流变网侧套管末屏结构,详细设计并实现了基于Windows操作平台的套管在线监测系统。该系统考虑了环境条件、电压采集、信号干扰等因素,全面监测套管的运行状态,以保证换流变设备的安全稳定运行。该系统已在贵广I回直流工程的安顺换流站成功应用。     

主变500kV环氧树脂浸纸套管介损异常原因研究

2001年至今,国内有多家电厂主变500 kV的12具环氧树脂浸纸套管发现介损异常,其中3具已予以更换.通过理论分析、现场实测,以及实验室研究,揭示了环氧树脂浸纸主变高压套管介损异常的原因主要是由于两种不同介质的界面极化所致,建议只要采取额定运行电压下持续运行一段时间的方法,即可使其介损恢复正常.对于该型套管的介质异常应.同时监测介损异常套管的电容量,以作出正确的判断.     

套管分压系统的过电压响应特性研究

研究了一种基于变压器套管末屏的过电压在线监测系统,使用电磁暂态软件ATP对其核心的套管电容分压系统进行了建模仿真。通过对模型阶跃波响应特性的仿真研究,并对比实验室实测的阶跃波响应结果,证实了仿真方法的有效性,为进行其他类型或其他电压等级套管类似系统的设计提供了有用的手段;此外通过对系统施加雷电和操作冲击电压波的仿真,得到其输出波形响应,验证了利用套管电容分压实现电网过电压在线监测的可行性。     

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.