互感器校验仪不确定度的评定

校准和测量能力(CMC)是校准实验室在常规条件下能够提供给客户校准和测量的能力,是常规条件校准中可获得的最小的测量不确定度。文章根据新的校准和测量能力表示方式,以测量重复性带来的不确定度分量为例,对互感器校验仪的测量不确定度进行重新评估和计算。通过评估和计算,更加规范、准确地表示了校准实验室的校准和测量能力。     

电力互感器不确定度评定

根据JJG 1021—2007《电力互感器》、JJF 1059—1999《测量不确定度评定与表示》、JJF 1069—2007《法定计量检定机构考核规范》、JJF 1033—2008《计量标准考核规范》等标准及规范制定了电力互感器比值差、相位差测量不确定度的评定方法,在其B类评定时,除考虑标准电流、电压互感器引入的不确定度分量外,还应考虑环境电磁干扰、误差测量装置以及二次负荷误差引入的不确定度分量。     

电流标准互感器测量结果不确定度评定

以《JJF1059-1999》为规范,对电流标准互感器测量结果不确定度进行评定。为更细化表征合理地赋予被测量之量的分散性,分别对电流标准比值差测量结果与相位差测量结果进行了科学分析的评定,从而确定了该标准器的校准测量能力,为确立陕西电力系统电流最高标准提供了依据。     

电流标准互感器测量结果不确定度评定

以《JJF1059-1999》为规范,对电流标准互感器测量结果不确定度进行评定。为更细化表征合理地赋予被测量之量的分散性,分别对电流标准比值差测量结果与相位差测量结果进行了科学分析的评定,从而确定了该标准器的校准测量能力,为确立陕西电力系统电流最高标准提供了依据。     

电能表、电流互感器测量结果的不确定度评定

依据JIF1059－1999《测量不确定度评定与表示》，JJF1033－2001《计量标准考核规范》的理论和有关规定，结合发电厂，供电局的实际情况，以实例形式详细分析了电能表，电流互感器测量结果的不确定度。为发电厂，供电局在建立电能能，电流互感器标准装置埋，提供了评定测量不确定度的方法。     

电流互感器测量误差的不确定度评定

通过对电流互感器的误差测量结果的不确定度来源进行分析,给出了其误差不确定度的完整评定过程和评定结果。     

互感器检定装置测量不确定度分析

文章介绍了不确定度评定的意义,对电流互感器检定装置的不确定度进行了分析,并通过实例对0.05级电流互感器检定装置测量结果的不确定度进行了评定.对完整而准确地评定电流互感器检定装置的测量不确定度具有指导意义,可供建标、校准、比对工作中不确定度评定作为参考.     

0.002S级双级电流互感器校准结果的不确定度评定方法

校准不确定度能够全面说明计量设备校准能力的优劣,成为考核电能计量标准装置综合性能的重要依据,文中以实例给出0.002S级双级电流互感器不确定度评定方法及其验证方法,评定结果给出了校准不确定度的可靠程度,为电流互感器的校准工作提供参考。     

电子式互感器校验仪测量结果不确定度评定

对电子式互感器校验仪的测量条件和测量模型进行分析,并对标准不确定度和扩展不确定度进行评定,通过传递比较法进行验证,证明了数据的合理性。     

数据采集系统测量结果的不确定度评定

依据数据采集系统的校准方法，对数据采集系统测量准确性影响的不确定度因素（来源）进行分析，确定被校准的数据采集系统与不确定度来源之间的关系。用适当的方法确定各不确定度来源的不确定度，根据测量不确定度传播定律，计算出被校准的数据采集系统测量结果的不确定度。     

基于随机模糊理论和改进马尔科夫法的变压器寿命评估

为了全面评估变压器的剩余寿命,从变压器性能衰退的角度和健康指数特性出发,考虑变压器寿命相关因素,采用变压器寿命评估三级系统,给出了变压器历年健康指数计算方法。基于变压器的历年健康指数,在传统马尔科夫预测模型的基础上,建立了改进的马尔科夫预测模型。考虑了不确定性因素对模型的影响,进行了不确定性修正,实现对变压器的寿命预测。通过某火电厂的实际算例验证了评估方法的可行性。     

110 kV无载调压变压器更新改造方案技术经济性探讨

介绍了对ＳＦ７－３１５００／１１０型无载调压变压器更新改造方案进行评价选择的分析计算方法,对１１０ｋＶ无载调压非节能型变压器更新或改造的经济效果问题进行了探讨,说明了对该型号器进行改造或更新不仅有利于稳定供电电压,还能提高供电企业的经济效益。     

A semiconductor H-bridge connection to avoid saturation in current transformers for differential protection

Current transformer saturation can be the cause of misoperation or false tripping in power transformer differential relays during connection transients. To avoid this scenario, the authors propose a solution based on a current transformer flux controller system (CT-FCS). The CT-FCS consists of a controlled semiconductor H-bridge connected to the primary winding of current transformers, allowing the inversion of the currents polarity. Unipolar pulses with high content of DC current are converted into bipolar pulses that reduce or cancel the amount of DC component in current transformer cores. By canceling the DC component, a saturation-free operation can be obtained. The use of this method will allow the selection of current transformers with lower saturation factors and will reduce the size of such devices.     

Avoiding sustained oscillations in power systems with tap changing transformers

The problem of avoiding sustained oscillations in power systems with dynamic loads and tap changing transformers is analyzed. Deadband size adjustment is used to eliminate limit cycles which originate from tap–load interactions. The analysis demonstrates the role of load dynamics in providing a deadband setting which guarantees the absence of sustained oscillatory behavior.     

Probability approach to installation studies of power transformers

A probability approach to transformer installation studies which have traditionally been based on very conservative deterministic criteria is described. The Monte-Carlo technique is used to evaluate the distribution function of the insulation deterioration with respect to the stochastic nature of load, ambient temperature and emergency loading. A statistical analysis is made to guarantee that a preestablished risk (R₀) associated with the operation is not exceeded. Owing to the fact that the transformer insulation is not regenerative, the concepts of ‘life expectancy’ and ‘rate of insulation deterioration’ are used in order to calculate the permissible peak loads.     

110 kV变电所两线三变桥接线的设计要点

110 kV变电所采用两线三变的桥接线模式,通过放大导线截面、减少线路回数,节约了线路走廊,降低了投资,缩短建设周期,但增加了保护和操作的难度,在苏州地区尚处在试点和推广阶段.对110 kV变电所两线三变桥接线模式中的电气主接线、保护配置、总平面布置等方面的设计要点进行了探讨.     

锅炉烟气BF式干法脱硫脱硝技术分析

通过对锅炉烟气BF式干法脱硫脱硝技术国内外的应用情况、原理、技术特点、系统特点及其经济性的分析，提出了选择脱硝技术的几个原则，肯定了这种方法是一种值得推荐的脱硫脱硝技术。     

Harmonic cancellation characteristics of specially connected transformers

Specially connected transformers such as V–V, Scott and Le-Blanc transformers are used to convert a three-phase supply into one or two single-phase supplies. These transformers are commonly used in the electro locomotive traction systems. This paper investigates the harmonic cancellation characteristics of such transformers. The results show that when two harmonic-producing loads are connected to each single-phase side of the transformers, the harmonics produced by the loads will cancel out at the primary sides of the transformers. The amount of cancellation is affected by transformer type and harmonic order. The study is performed for seven types of specially connected transformers.     

热电厂220 kV 配电装置及变压器布置优化设计

电厂升压站设计应该结合工程实际情况开展深入分析,制定技术可靠、经济最优化的设计方案。北京某电厂220 kV升压站无法像常规工程那样布置在燃机房A排外独立的区域内,需要将220 kV升压站与燃机房A排外变压器结合布置,此举不仅优化了总平面布置,而且提高了空间利用率,使功能区间更明显,提高了设备可靠性和运行安全性,设备布置方式灵活、运行维护工作量少、设备安装检修便利,使电厂整体环境友好,同时也兼顾了远景扩建时的需求。     

Bragg system for temperature monitoring in distribution transformers

Heat represents the energy loss occurring in the core and coils of a transformer. The designer must be able to predict the temperature throughout the transformer, in order to correctly determine the amount of copper and silicon steel sheet and the type of cooling ducts and insulation needed to prevent excessive hot spots. This paper presents a pilot design of a distribution transformer monitor using Fiber Bragg Grating (FBG) technology to determine the temperature at 12 points distributed along the LV and HV coils employing three optical fibers. A 100 kV A single-phase distribution transformer was utilized in order to accurately find and measure the hot spot. The thermal equivalent circuit model was built according to the heat transmission process in a transformer. The radiation and convection resistance values of this model are determined iteratively until they border on the FBG measurement results.