Improved modelling of power transformer winding using bacterial swarming algorithm and frequency response analysis

The paper discusses an improved modelling of transformer windings based on bacterial swarming algorithm (BSA) and frequency response analysis (FRA). With the purpose to accurately identify transformer windings parameters a model-based identification approach is introduced using a well-known lumped parameter model. It includes search space estimation using analytical calculations, which is used for the subsequent model parameters identification with a novel BSA. The newly introduced BSA, being developed upon a bacterial foraging behavior, is described in detail. Simulations and discussions are presented to explore the potential of the proposed approach using simulated and experimentally measured FRA responses taken from two transformers. The BSA identification results are compared with those using genetic algorithm. It is shown that the proposed BSA delivers satisfactory parameter identification and improved modelling can be used for FRA results interpretation.     

Thermal modeling of disc-type winding for ventilated dry-type transformers

A thermal model for disc-type winding of ventilated dry-type power transformers is presented. The proposed model was based on fundamental heat transfer mechanisms, i.e. heat conduction, convection and radiation. All cooling surfaces were identified, and heat transfer coefficients for each identified surface were presented. The thermal model was applied to a ventilated dry-type power transformer rated at 2000 kV A under different load conditions. Temperature distributions were calculated, and the hottest-spots were located accordingly. The temperatures for the predicted hottest-spots were measured by an infrared thermometer, and they were compared with the temperatures calculated by the model. They are in good agreement.     

抽水蓄能电站用变压器的结构分析与参数计算

对抽水蓄能电站用变压器的两种可用结构的运行情况和经济性能进行了分析,着重对第二种结构在半压启动电动机过程中的联结组别,短路阻抗,纵向涡流损耗三个参数用计算公式进行了推导。     

Design of the winding–bushing interconnections in large power transformers

The paper presents the improvement in design of the conductor connecting the windings and bushings in oil power transformers. This is a sensitive part of large transformers and there is a need to optimise its manufacturing time and costs. The thermal problem of the heating of this conductor with increased insulation thickness on a part of it is treated using a non-linear two-dimensional thermal model. The experiments performed made determining of some problematic parameters (heat resistance of oil-paper insulation and the paper to oil convection heat transfer coefficient) of the thermal model feasible. The results obtained are of practical interest in the design practice of interconnections, but also affect the important parameters of heat transfer by devices with oil immersed paper insulation.     

变压器绕组变形的扫频短路阻抗法研究

针对变压器因绕组变形而产生故障问题,分析了现有短路阻抗法和频响法检测绕组变形手段的特点和不足,研究了扫频短路阻抗法的基本原理和测试接线方式,在模型变压器上进行了绕组层间短路、绕组匝间短路等不同情况的试验测试,初步验证了该方法的有效性。以某220 kV变压器为测试对象,采用扫频短路阻抗法进行了变电站现场测试工作。该方法测试结果能够提供更多的测量参量,为绕组变形的研判提供了更多的参考依据,是一种很有价值的变压器绕组变形测试方法。     

Temperature distribution in foil winding for ventilated dry-type power transformers

Predicting temperatures of transformers is important in order to prevent the deterioration of electrical insulation since the life of the transformers corresponds with that of the insulation. Reports of thermal behavior of ventilated dry-type transformers are rare in the literature. In particular, foil winding has received little attention despite their wide usage in practice. In this study, a thermal model for foil winding was proposed and temperature distributions were determined by the finite element method (FEM). In order to cope with the non-uniformity of the heat fluxes in the foil winding due to induced currents, different convection coefficients and varying air temperature along the vertical height of the foil winding were suggested and applied to the thermal model. The thermal model was solved by coupling it with the electromagnetic model to calculate the non-uniform power losses. The model was applied to a ventilated dry-type power transformer rated at 2000 kVA. Experimental temperatures were measured with thermocouples, and used to verify the finite element results. They showed reasonable agreement and will provide a useful tool for transformer engineers.     

S11系列卷铁心与叠积式铁心变压器的性能分析

介绍了S11系列卷铁心变压器和叠积式铁心变压器的结构特点,并根据各自的结构分析了其空载损耗、空载电流、承受短路的能力和过负载能力等性能。认为在抗短路能力和过负载能力方面,叠积式铁心变压器优于卷铁心变压器;对小容量变压器,卷铁心变压器具有成本优势,而对于大容量变压器,叠积式铁心变压器的制造成本低于卷铁心变压器。     

Calculation of inductance of single-tooth winding

A simple method for calculating leakage inductance of tooth-pole windings of multipole synchronous AC motors is proposed.     

三绕组变压器中压绕组短路电动力的计算方法

针对220 kV/180 MVA三绕组电力变压器出口短路时短路电流的计算问题,从磁势平衡原理出发,建立了在中压绕组短路工况下中压绕组短路力的计算模型,利用"场-路耦合"有限元方法计算了该模型的二维瞬态漏磁场,获得了中压绕组线饼的受力分布和瞬变曲线,并对受轴向短路电动力作用最大线饼的轴向稳定性进行了校核。计算结果表明,利用有限元软件ANSYS对三绕组变压器中压短路工况下中压绕组短路电动力的计算方法,省去了传统计算电动力复杂的计算过程及一些计算假设,提高了计算精度,变压器的中压绕组具有足够的轴向机械强度,对变压器设计和运行人员有一定的参考价值。     

三绕组变压器低压绕组幅向短路力的计算方法

阐述了低-中-高结构的三绕组电力变压器低压绕组幅向短路力的计算方法,即从磁势平衡原理出发,导出了求解该变压器最严重短路情况下低压绕组幅向力的计算模型,利用“场-路耦合”有限元方法计算了该模型的二维瞬态漏磁场,获得了低压绕组线饼的受力分布和瞬变曲线,并对受力最大的线饼进行了抗幅向失稳能力校核.该计算方法简化了传统计算电磁...     

变压器绕组直流电阻不平衡原因的分析

根据现场三相变压器绕组直流电阻测量的结果,总结分析了绕组直流电阻不平衡率超标的原因及吊检处理方法.     

偏心及返回导体对特高压用计量CT误差影响分析

为明确电能计量装置自身误差受电磁场影响程度,对特高压用计量电流互感器(CT)开展一次绕组偏心及返回导体对误差影响的定量分析。首先根据磁路平衡原理建立在圆柱坐标内CT误差数学模型,推导出不同位置的外加磁场点对CT误差影响计算公式,并结合实例得到有限元与解析解结果一致,证明推导公式的正确性;然后在二维电场中对1 000 k V工程中典型CT尺寸及一次电流进行磁场分布仿真,定量的得到对于特高压用计量CT,一次绕组偏心大于1/8的CT半径后会铁心内部会产生局部饱和,导致误差产生突变进而导致超差可能;此外,仿真结果指出外部返回导体距离CT中心应大于3倍CT半径后,返回导体引起的磁场对CT误差的干扰才能被忽略;最后搭建实际特高压误差测试平台对一次绕组偏心开展试验,测试数据与仿真结果趋势一致。     

Generalized analytical formulae to compute electrical characteristics of a homogenous ladder network of the transformer winding

Many electrical systems are expressed as a complex ladder network consisting of combinations of resistances, inductances, and capacitances. Computation of electrical characteristics, such as voltages, currents, and equivalent impedances of these ladder networks require the solution of complicated differential‐algebraic equations that are quite tedious and cumbersome. The earlier works have given particular attention to purely resistive ladder networks ignoring the inductance and capacitance parameters. Moreover, there are no direct expressions available to quickly compute these characteristics. This paper derives generalized analytical expressions that can be directly used to obtain the electrical characteristics of a finite as well as semi‐infinite homogenous ladder network by simply plugging the values of its constituent parameters. Expressions are deduced for excitation source applied to the input terminal and across 2 arbitrary nodes, respectively. Kirchhoff mesh and node laws along with ordinary algebra and trigonometric theorems are applied to derive these expressions. Boundary‐value technique is used to circuit equations to determine unknown coefficients of the expressions. The derivation given in these paper would surely help the readers to quickly compute the electrical characteristics without solving recursive circuit equations and avoiding complex state‐space matrices.     

110kV平沙站站用变系统缺陷分析及改进措施

分析了110kV平沙变电站站用变系统实际运行中的缺陷情况,探讨导致缺陷的原因并提出了正确的改进措施,从而保证了平沙站站用变系统的可靠运行。     

Sweep frequency response analysis (SFRA) for the assessment of winding displacements and deformation in power transformers

The sweep frequency response analysis (SFRA) is an analysis technique for detecting winding displacement and deformation (among other mechanical and electrical failures) on power and distribution transformers. Nowadays, there is an increasing interest in SFRA method because of its sensibility in detecting mechanical faults without opening the unit. SFRA as a diagnostic technique must integrate both the off-line measurements and the interpretation of the data in order to provide an assessment of the condition of the windings. However, guidelines for the measurement and record interpretation are not available. The evaluation is presently done by experts in the topic through the visual inspection or with the help of statistical parameters such as the correlation coefficient and the standard deviation. However, criteria like the limits of normal variation of the parameters, and the features observed in the records in the presence of a determined type of fault could not to coincide. Although, there are some proposals for making the interpretation more objective, neither of them integrate human expertise along with the different kind of parameters obtained from the evaluation of the records in a diagnostic model. This paper presents a survey on the alternatives in the measurement techniques and interpretation of SFRA measurements, describing some sources of uncertainty in applying this methodology.     

A new method for comparing the transfer function of transformers in order to detect the location and amount of winding faults

Since the transfer function (TF) is an acknowledged method for detecting power transformer faults, introduction of a proper manner to compare these TFs is necessary. Although a lot of effort has been made, proposed methods are not reliable. This paper presents a new approach based on weight functions, compared with all other methods. This comparison shows that the weight function method is much more effective than the others.     

自耦变压器公共绕组过负荷原因分析

自耦变压器在某种运行方式下,高压侧和中压侧还未到达额定容量,而公共绕组就已过负荷告警。对此,为什么会出现上述情况以及如何改善运行方式才能使得主变压器尽可能满载运行进行了研究,首先通过对自耦变压器进行建模分析,推导出教学方程式,根据不同的运行方式进行分析,得出问题的原因,即自耦变压器在高压侧和低压侧同时向中压侧输送功率时,当公共绕组到达额定功率,高压侧和中压侧输送功率不能达到满功率输出,然后,以一个具体变电站的实际运行数据进行计算,验证了理论分析的结果,并提出了使自耦变压器尽可能地满负荷运行的方法：一要提高功率因数,二要减少由低压侧中压侧输送的无功功率。     

一起220kV变压器低压绕组断线故障的分析处理

对一起220kV变压器低压绕组断线故障进行了分析,并提出了改进措施。     

220kV变压器高压侧直流电阻超标原因分析及处理

本文中作者介绍了一起220k V变压器高压侧直流电阻超标缺陷发现的过程,分析了缺陷发生原因,阐述了缺陷处理过程,并提出了相关建议。     

运行时间较长的变压器短路故障损坏的分析

介绍了变压器短路故障损坏的原因,分析了故障实例,并提出了解决方法。