应用马尔科夫模型评估电力变压器可靠性

为对电力变压器进行可靠性评估,首次提出了基于马尔科夫过程的电力变压器可靠性评估模型。该法将变压器所处的使用状态分为正常运行、绕组故障、预防性试验等11种状态,针对变压器可靠性指标统计数据,结合马尔科夫过程,同时运用频率和持续时间法,建立了综合的变压器可靠性评估模型。通过对变压器可能所处的各个状态概率和其它一些可靠性指标的计算,验证了该模型的正确性。基于马尔科夫过程的电力变压器可靠性评估模型能较准确客观地对变压器可靠性进行量化评估,并且计算简单,具有较强的可操作性,所提出的评估方法为全面分析变压器状态从而制定变压器维护维修策略提供了理论支持。     

500 kV 自耦变压器绕组短路特性分析

因自耦变压器具有体积小、效率高、电压变化率低等优点,目前被广泛应用在特高压建设的骨干网架中,但近年变压器短路频发,对电网带来严重影响,而500 kV 等级自耦变压器所占比例很大,因此对500 kV 自耦变压器短路性能展开研究非常重要。为此,基于有限元方法,根据实际500 kV 自耦变压器参数,建立了绕组的场–路耦合模型,验证模型的正确性,并根据绕组实际电气连接特点,考虑低压–公共绕组运行和公共–串联绕组运行两种情况,计算绕组漏磁场和短路电动力并进行对比分析,总结漏磁密及电动力分布相应规律,所得结果可大大提高电网的安全可靠性。     

基于关联分析的变压器在线监测方法研究

本文中作者在电力大数据的基础上采用关联分析方法研究变压器绕组温升和负载率的关系,并推算在不同负载率水平下各相绕组的正常温升范围。通过对变压器实际运行数据进行建模和算例分析,验证了该模型可以通过变压器绕组的温度信号对变压器的运行状态进行初步判断。     

漏电抗的参数辨识技术在线监测变压器绕组变形的研究

短路电抗法是检测电力变压器绕组变形的有效方法之一,在线检测变压器短路电抗变化对随时获取绕组的健康状况具有重要意义。为了实现变压器绕组的在线监测,基于一台模型变压器,以变压器回路方程作为参数辨识模型,利用递推的最小二乘算法对绕组漏电感参数进行实时辨识。分析和计算了测量系统产生的误差,提出了采用类似模糊神经网络的方法对PT和CT进行补偿。通过对比在线测量值与离线测量值的结果,表明该测量系统具有良好的准确性与稳定性,变压器的运行状态对测量结果影响很小,能够为实际运行中的变压器的绕组状况提供实时准确的指示。     

基于SOGI的变压器短路阻抗参数在线辨识方法

电力变压器在运行过程中发生绕组变形导致的内部故障,已经严重危害电网安全。为了及时发现变压器绕组变形故障,文中以变压器回路方程为基本模型,提出了一种变压器绕组参数在线辨识方法。通过分析变压器暂态和稳态两种运行状态,建立不同的参数辨识模型,推导了不同状态下变压器绕组参数辨识方程。利用二阶广义积分器提取变压器原、副边电压电流信号基波和各次谐波分量,判断变压器的运行状态,通过最小二乘算法进行实时辨识,实现对变压器绕组变形的监测。建立了变压器绕组变形的仿真模型,通过仿真模型及动模试验验证了变压器参数辨识在线监测系统的可行性。     

基于多源信息的变压器状态评价方案研究与应用

为了适应变电设备向大容量化、高电压化、结构多样化、密封化及设备状态检修的发展趋势,笔者在区间物元可拓原理、云模型和灰色模型的组差值法的基础上,建立基于多源信息的变压器两级和综合评价模型,给出了变压器单因素指标的趋势预测评价和整体状态评价的具体方案。在两级评价中利用顶层油温、绕组热点温度和负载能力计算综合相对劣化度并得到自然模式和加速劣化模式的综合评价分值,在综合评价中利用统计模型得到不良工况和可靠性对运行状态进行补充,首次建立负载能力模型和故障预测模型,对变压器运行状态进行修正。该评价模型克服了传统状态评价方法的缺陷和不足,对其他变电设备的状态评价流程有较好的指导作用。最后,基于文中评价模型对超高压公司实际运行的1号变压器开展评价分析,结果与该变压器实际情况较为吻合。     

基于状态评价的老旧变压器大修改造工作分析

运行15年以上的老旧变压器处于其生命周期的耗损失效期,为了降低老旧变压器在运行中发生事故的风险,运用状态评价模型对这些变压器进行状态评价,总结出这些变压器主要存在附件老化失效、短路冲击严重及油质绝缘下降等问题.通过采取组配件升级改造、现场对绕组加装付压板以及吸附滤油等方法有效地解决了老旧变压器的问题,提高了老旧变压器运行的可靠性.     

基于振动频响法的变压器绕组松动故障检测方法研究北大核心CSCD

变压器是电力系统的重要设备,在长期运行中会出现绕组松动、变形等故障,影响电力系统的正常工作,因此对变压器绕组健康状态进行评估极为重要。提出利用振动频响法获取变压器绕组的振动频响函数,对比绕组故障状态与健康状态下的振动频响函数,将两者之间的相关系数作为判断变压器绕组故障与否的依据。随后,对比健康状态与4种不同程度松动状态下变压器绕组的振动频响函数,探讨利用相关系数判断变压器绕组松动故障程度的可行性。本研究结果对判断变压器绕组运行故障具有一定的指导意义。     

一种变压器绕组状态在线诊断方法的研究

提出了一种不受变压器运行条件约束的绕组在线诊断方法。在线采集实际运行中的变压器振动数据,分析振动数据并获取变压器振动曲线,振动曲线结合绕组理论模型,最终获得变压器绕组运行状态。该方法与被测变压器没有电气连接,对设备的正常运行无任何影响,可以安全、可靠地达到诊断目的。     

变压器绕组振动监测技术研究综述

变压器绕组状态的监测分析是及时发现故障隐患、确保其安全可靠运行的重要手段,振动分析法从变压器绕组的机械动力学特性出发,根据监测到的振动信号中所包含的设备信息对绕组状态进行分析评估,在变压器绕组状态监测领域发挥着重要的作用。从变压器绕组振动监测技术的基本原理出发,分别从变压器绕组振动特性的建模计算与试验研究、基于振动信号的变压器绕组状态监测方法等方面综述了近年来变压器绕组振动监测领域的重要研究成果;最后,探讨现有变压器绕组振动监测领域的存在问题及相关研究方向,为今后变压器绕组振动监测技术的发展提供参考。     

计及风电场的发输配电系统可靠性评估

考虑风速时序性和自相关性的特点,建立了风速的自回归移动平均(auto-regressive and moving average,ARMA)模型,并结合常规机组、线路和变压器等状态模型,建立了基于蒙特卡罗仿真方法的风电场可靠性模型,对含风电场的发输电组合系统进行可靠性评估,同时建立了发输电组合系统的多状态机组等值模型,将该等值模型与配电系统相结合,计算了平均停电频率和停电电量损失等配电网可靠性指标,通过分析和比较可靠性指标研究了风电场对配电系统可靠性的影响,结果表明风电机组的接入对提高电力系统可靠性具有一定的作用。     

A basic framework for generating system operating health analysis

A probabilistic technique is presented in this paper to assess the operating reserve requirements in a system. In this approach, the generation system is classified into different system operating states. This technique combines deterministic with probabilistic indices to monitor the well-being. The system well-being as designated by deterministic criteria are identified as being healthy, marginal and at risk. A risk index designated as the generating system operating state risk (GSOSR) is defined in this paper as the probability of residing in an undesirable operating state. Technique together with the effect on the GSOSR and the system operating state probabilities of factors such as lead time, system peak load, load forecast uncertainty and generating unit derated states are illustrated by application to the IEEE-RTS (reliability test system)     

应用工业安全可靠性评价技术评价电力变压器的探讨

运用最新工业安全可靠性评价技术(网络模型法、故障树法、马尔可夫模型法、故障模式和失效分析法),深入分析了重要的输变电设备--电力变压器的可靠性.计算了变压器串联和并联模型的可靠度;构建了变压器故障树简化模型,并进行了定性和定量分析;构建了变压器马尔可夫状态转移模型,并介绍了多种可靠性指标的计算方法;介绍了故障模式和失效分析的步骤和实例.     

带变权的电力变压器状态模糊综合评判

针对常权无法客观反映电力变压器部分参数偏离正常值时对整体评估影响的不足,提出了带变权的状态综合模糊评判方法。通过分析影响变压器状态主要方面的特征参量,建立了层次型评估指标体系;在用层次分析法确定指标常权的基础上,引入了基于均衡函数的变权模式,综合考虑指标间的均衡性,并根据实际数据偏离正常值的大小,对常权修正得到变权;最后利用模糊理论确定单因素对各状态等级的隶属度,并基于多级模糊评判的思想分别对各层进行评判,综合得出了变压器状态。用实例比较变权与常权模糊评判的结果表明,应用基于均衡函数的变权综合比常权更合理、客观,其评判结论更接近变压器真实的运行状态。     

大型变压器的可靠性分析

大型变压器的失效应分成两类加以研究。第一类失效对应于变压器较严重的事故,研究这类失效应把变压器看成是不可修复的系统,其最主要的指标为失效率。本文提出了可靠性数据处理和失效率’计的方法。通过对变压器第一类失效的特点和主要原因进行深入分析,得到了110kv及以上变压器可靠性的控制指标。第二类失率对应于变压器故轻的故障,研究这类失效应把变压     

The impact of random failures on nodal price and nodal reliability in restructured power systems

Power system deregulation provides customers choices on electricity regarding price and reliability. This paper investigates the impact of random failures on the nodal price and the nodal reliability in a restructured power system. The expected nodal price and the associated standard deviation are introduced to incorporate the effect of random failures on the nodal price. Nodal reliability indices rather than conventional reliability indices used in vertically-integrated power systems are used in this paper to represent customer load point reliability in a restructured power market. A probabilistic technique, which combines the reliability assessment approach and the optimal power flow (OPF) method, is developed to determine the expected nodal price and the associated expected nodal risk. The price fluctuation and the corresponding probability for each system state are also presented. The relationship between the nodal price and nodal reliability are also investigated and discussed in this paper.     

A Monte Carlo method for multi-area generation system reliabilityassessment

The authors present a method for multiarea generation system reliability assessment. It is based on direct sampling of generating unit states, the clustering technique, and the correlative normal distribution sampling technique of the load states. A linear programming model was used to minimize the total load curtailment. Area load uncertainty, correlation between area loads, and generating unit derated state were considered. Incorporation of these factors does not create a significant increase in computing time. Sensitivity indices of both system and each area to area generation and tie line capacities can be calculated. These indices provide information regarding which tie line or which area generating capacity should be reinforced from the overall system and each area point of view. Calculation results of a four-area system are given to demonstrate the effectiveness of the method     

基于FD—MonteCarlo混合法的节点电价和节点可靠性指标评估

电力市场环境下,节点电价和节点可靠性指标能提供系统运行的经济信息和风险信息。为研究市场条件下元件随机故障和计划检修对节点电价和节点可靠性指标的影响,在应用MonteCarlo法模拟系统状态转移的过程中,采用Frequency—DurationTime（FD）法解析地计算确定性事件和随机事件发生后状态的期望持续时间。考虑到可中断负荷缓解系统阻塞和抑制节点电价的作用,设计了一个2层优化模型来确定节点电价和负荷中断量,并提出了一种启发式算法进行求解。最后以一个6节点的可靠性测试系统（RBTS）为例对所提模型和算法进行了说明。     

Reliability evaluation of distribution transformers with high penetration of distributed generation

In this paper, a novel methodology is presented to evaluate the micro-grids reliability concerning the dynamic thermal aging failure of transformers. The widespread presence of distributed generation (DG) units reduces the loading passing through the distribution transformers and consequently improves the dynamic thermal failures. The system reliability is investigated for various penetrations of different scenarios from the view of DG technologies. The introduced method is applied to a realistic distribution system comprising different distribution transformers in Iran. The sensitivity analysis corresponding to adequacy indices such as expected energy not-supplied (EENS) based on DG penetrations is performed. By the use of the novel methodology proposed, it is possible to recognize how different DG technologies and penetrations can impact on the system reliability. The results demonstrate that the diesel generators and hybrid systems including diesel generators, photovoltaic units, and wind turbines are the most promising DG technologies to improve the transformer failures and the reliability of micro-grids compared with renewable DG units.     

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.