利用磁通轨迹特征识别变压器励磁涌流

提出了一种基于磁通轨迹特征的变压器励磁涌流识别方法。该方法利用实测的变压器电压和电流量来推算变压器主磁通的轨迹,通过提取主磁通轨迹的特征来判断主磁通变化范围,从而确定变压器是否发生励磁涌流。仿真和实验结果证明了识别方法的可行性.     

基于磁通轨迹特征的变压器励磁涌流识别新方法

介绍了变压器保护正常动作率的现状,分析了当前比较流行的变压器励磁涌流判断方法,并指出缺陷。提出了一种基于磁通轨迹特征的变压器励磁涌流识别新方法,该方法根据变压器发生内部故障时铁心不饱和,而出现励磁涌流时铁心饱和的原理,利用实测的变压器电压和电流量推算变压器主磁通的轨迹,通过提取主磁通轨迹的特征来判断主磁通变化范围,从而确定变压器是否发生励磁涌流。仿真结果证明了识别方法的可行性。     

励磁涌流鉴别方法在变压器保护中的应用

励磁涌流的鉴别一直是变压器保护中的一个关键问题,文中针对目前国内外学者提出的励磁涌流识别原理和方法进行了分析和综述.并对目前现场采用的方法和一些现代智能理论鉴别中的应用进行了比较,指出了变压器励磁涌流在鉴别方法的研究和应用动向.     

变压器衰减励磁涌流的实用计算方法

分析了变压器励磁涌流的衰减机理，根据变压器等效电路，推导出衰减励磁涌流的递归计算方法。通过曲线拟合的方法，提出了涌流幅值和间断角随时间变化的实用计算公式，为变压器差动保护和后备保护的原理研究、整定计算提供了分析计算的工具。     

励磁涌流鉴别方法在变压器保护中的应用

励磁涌流的鉴别一直是变压器保护中的一个关键问题 ,文中针对目前国内外学者提出的励磁涌流识别原理和方法进行了分析和综述。并对目前现场采用的方法和一些现代智能理论鉴别中的应用进行了比较 ,指出了变压器励磁涌流在鉴别方法的研究和应用动向     

变压器衰减励磁涌流的实用计算方法

分析了变压器励磁涌流的衰减机理,根据变压器等效电路,推导出衰减励磁涌流的递归计算方法。通过曲线拟合的方法,提出了涌流幅值和间断角随时间变化的实用计算公式,为变压器差动保护和后备保护的原理研究、整定计算提供了分析计算的工具。     

变压器的励磁涌流及抑制方法

分析了变压器励磁涌流的产生机理、计算方法、特点及危害。通过具体事例阐述了控制合闸相角、合闸回路串联电阻及低压侧并联电容器等对变压器励磁涌流的抑制作用。     

基于差流符号序列特征的变压器励磁涌流识别判据

变压器在空载合闸的过程中,会产生幅值较大的励磁涌流,如不采取相应的闭锁措施,将导致变压器差动保护误动作。针对该问题,提出了一种基于差流符号序列特征的变压器励磁涌流识别判据。该判据首先对差流序列进行符号化处理,根据符号序列中相关模式序列出现的比例,量化表征差流波形的特征,实现对励磁涌流和故障差流的识别。利用PSCAD/EMTDC仿真软件验证了所提判据在各类区内外故障和励磁涌流工况下,以及各类工况伴随电流互感器饱和时的有效性。     

利用电流波形特征识别变压器励磁涌流和故障电流

提出一种利用波形特征快速区分变压器励磁涌流和内部故障电流的新方法。该方法基于涌流波形畸变严重,会呈现出尖顶波的凹弧特征,而故障电流基本保持正弦特征的思想,首先找出10ms数据窗内采样值的绝对值取得最大值的点,然后计算该点两侧相邻的2个采样步长组成的大梯形面积与2个单采样步长组成的小梯形面积和的差的总和来区分变压器励磁涌流和内部故障。动模实验表明：该方法能够快速切除变压器内部故障,动作时间约为10ms,所需时间较短,识别灵敏度高,并且实现方便,不受电流非周期分量的影响。     

Identifying magnetizing inrush in power transformers based on symmetry of current waveforms

This letter proposes a novel method for the discrimination between magnetizing inrush and internal fault in power transformers based on the similarity of the current waveforms. The proposed method first normalizes and sorts the sample points of the differential current in a full fundamental frequency cycle to obtain a new sequence which is independent of the magnitude and initial phase angle of the original signal. Afterward, three indices are introduced to measure the similarity between the new sequence and a template, which are used to discriminate the inrush from an internal fault. Simulation studies demonstrate the effectiveness of the proposed method and its advantages over the conventional second harmonic restraint method. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A novel magnetizing inrush current suppressor of energized transformers

The magnetizing inrush possibly occurs when the transformer is energized in the case of no load or a light load. The reason rests with the saturation state or even deep saturation state of the transformer core due to many factors such as inception angles, residual flux, and so on. Both the transformer itself and the power quality in the power system will be adversely impacted by the magnetizing inrush. By utilizing the tertiary winding of a three‐windings transformer, a new technique called ‘magnetizing inrush suppressor’ (MIS) is proposed to eliminate the inrush. When the transformer is switched on, it allows the voltage on the tertiary winding to climb gradually and ensures that the voltages on both sides have the same phase but different magnitudes. In this case, the inrush current can be eliminated successfully. Finally, simulation tests based on PSCAD are performed and analyzed in detail, and the validity of the proposed approach is confirmed. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Reducing the magnetizing inrush current by means of controlled energization and de-energization of large power transformers

Energizing unloaded transformers may result in magnetizing inrush current of high amplitude. These currents have many unfavorable effects including differential protection maloperation, deterioration of the insulation material and mechanical support structure of windings, voltage sag and other power quality issues on the HV, as well as on lower voltage terminal(s). If no point-on-wave controller is applied the energization of the transformer may occur at any time on the sinusoidal wave producing high inrush current peaks if the transformer core is driven into saturation. The point-on-wave control methodology presented in this paper has been elaborated to eliminate the inrush currents of 132/15 kV, Y/delta connected generator step-up transformers, which are switched very often in quick start, gas-turbine power stations. A new controller has been elaborated to operate the mechanically staggered, common drive type circuit breakers which are characterized by three-pole operated spring drive and fixed time delay between the operating poles. The paper proposes a new method to minimize the residual flux in the core by means of controlled de-energization. The new concept has been proved by several field tests and the new controllers have been put into service in several power stations in Hungary.     

Current transformer performance for inrush current in power transformers

A mathematical model has been developed for a current transformer to predict the transient performance during switch-in of a power transformer with residual flux.Typical 50 - 100 - 200/1 and 300/1 current transformers have been simulated and the secondary current response has been computed for different values of the current transformer time constants. The practical results are reported.     

基于最小二乘支持向量机的变压器励磁涌流识别方法研究

纵差保护是变压器的主保护,但在变压器空载合闸或者变压器外部短路故障被切除端电压突然恢复时会产生励磁涌流,可能会导致纵差保护的误动作,这将严重影响变压器的安全可靠运行.为此提出了一种基于最小二乘支持向量机(LS-SVM)的励磁涌流鉴别方法.选择二次谐波含量和间断角作为输入向量,利用具有高斯核函数的LS-SVM建立分类模型,对励磁涌流进行识别.仿真结果表明,该方法鉴别励磁涌流和故障电流有很高的识别率.该方法为减少变压器的误动和拒动提供了一种新的思路.     

基于模糊多判据的变压器励磁涌流识别新算法

在分析现有各种变压器励磁涌流识别算法的基础上 ,采用模糊集合理论 ,综合各判据的优点 ,得到一种较为理想的新算法 ,通过EMTP仿真计算 ,并考虑CT传变特性后 ,该模糊多判据算法能快速识别各种变压器内部故障和励磁涌流情况 ,克服了谐波制动原理在某些工况下的误判和延时动作问题     

电力变压器励磁涌流和故障电流仿真研究

在研究电力变压器励磁涌流和故障电流特性的基础上 ,应用电磁暂态程序 (EMTP) ,采用不同的模型和方法对变压器励磁涌流和故障电流进行了全面系统的仿真计算和分析。结果表明 ,EMTP能够根据不同的条件和要求有效地实现对变压器励磁涌流和故障电流的仿真