试论二次负荷功率因数对电磁式CT误差的影响

在简要分析电磁式电流互感器误差形成机理基础上,给出电流互感器的误差表达式。基于OMICRON公司的CT分析仪对表达式的二次负荷功率因数影响进行验证,并通过MATLAB仿真软件得到不同二次负荷功率因数的电磁式电流互感器误差影响曲线。试验结果表明：随着二次负荷功率因数的增大,电磁式电流互感器的比值差绝对值逐渐减小,相位差逐渐增大。当额定电流增大时,比值差和相位差误差受功率因数的影响变小,误差曲线较为平坦。     

TA回路接线错误原因及对策分析

新建或改扩建变电站投运前,模拟负荷通流试验无法正常进行。鉴于此,根据电流互感器接线方式和二次回路要求,在施工现场寻找电流互感器二次回路接线错误原因,制订相应对策,以尽量减少电流互感器二次回路的人为接线错误,确保电流互感器二次回路接线正确。     

二次压降校准点的分析与思考

JJF1619-2017《互感器二次压降及负荷测试仪校准规范》中规定了互感器二次压降及负荷测试仪校准工作的原理、方法、项目及要求等,是技术人员实验室校准工作的主要依据,但对于二次压降校准点没有具体规定,只提出了原则性要求。笔者根据多年来现场实际测试的二次压降大数据和实验室校准工作中遇到的各种问题,提出了二次压降校准点设置的见解供广大从事互感器二次压降及负荷测试校准工作的技术员参考。     

电压互感器二次压降仿真测试

电压互感器二次压降是影响电能计量准确性的重要因素之一,正确测量电压互感器二次压降是保证电能计量准确、计费合理的重要手段。针对电压互感器二次不同的联结方式设计了不同的二次压降仿真测试线路及算法,能准确模拟变电站和大用户电压互感器二次压降的误差测试,可广泛应用于电力系统电能计量专业的教学和培训中。     

浅析负荷对电压互感器误差的影响及对策

电压互感器是电力计量系统中不可缺少的计量、保护设备,它是电力系统安全及关口计量稳定可靠运行的保证。电压互感器的误差对实现计量关口结算和测控保护安全都有非常大的影响。在简述电压互感器检定方法和工作原理的基础上,分析二次负荷对互感器误差的影响和应采取的措施,以降低二次负荷对互感器误差的影响。     

互感器二次低负荷运行对电能计量的影响

介绍了计量用互感器二次低负荷运行对互感器误差的影响,并结合实际测试数据,提出了改进方法。     

电流电压互感器负荷箱原理性能分析

运用实验室互感器检定装置对互感器进行测试。在接入互感器负荷箱和不接入互感器负荷箱两种情况下，实验误差数据结果都存在差异。当接入负荷箱时，测得的误差数据相对稳定且在规程误差测量范围内；当不接入负荷箱时，实验误差数据会超出规程误差范围，特别是对负荷下限的误差影响更大，造成实验结果超过规程规定值，或使检定结果不准确，缺乏参考价值。阐述了互感器负荷箱结构、线路原理，分析了使用负荷箱的注意事项；通过负荷箱计量特性、技术指标及计量误差特性的介绍，阐明了电流、电压互感器负荷箱对误差实验数据影响的根本原因，以期对互感器质量评估具有一定的参考价值。     

互感器校验仪差值回路附加负荷与测量误差

分析介绍检定互感器时校验仪差值回路附加负荷造成的测量误差,以及互感器二次侧阻抗或导纳的测定线路和测量误差的计算方法。     

保护用电流互感器检定线路浅析

设计了专门针对保护用电流互感器的检定线路,能完成检定常用电流比互感器、检定特殊电流比互感器、实测二次负荷、增大输出电压和外接电源测伏安特性等五类测试。     

检定电流互感器时二次负荷的接入方法

根据现场检定电流互感器的要求,介绍了几种典型的电流互感器检定时二次负荷的接入方法,避免了因接线不当引起的附加误差,从而保证了测量的准确性。     

电流互感器误差影响因素与应用分析

电流互感器是电能计量装置重要组成部分,其误差是电能计量装置误差主要来源之一。本文分析了电流互感器误差的影响因素。分析表明：电流互感器的误差主要受两方面影响：一是电流互感器的结构,如铁芯尺寸、形状、材料以及线圈匝数;二是电流互感器的工作条件,即一次电流大小和二次绕组的负载阻抗,并就减小误差方法进行分析。最后,介绍了实际使用中如何根据参数选择合适的电流互感器。     

An innovative combined electronic instrument transformer applied in high voltage lines

For better performances, electronic instrument transformers are used to replace conventional electro-magnetic inductive current or potential transformers based on ferrous cores and windings to measure heavy current and high voltage in power system. But unpredictable stability, high price and unsatisfactory life hold back their industrializations. Employing the simple but reliable insulation structure of conventional transformer and the unconventional sensing methods of electronic transformers at the same time, an innovative combined electronic instrument transformer is presented in this paper. Performances of the prototype are estimated through relative tests, and the novel design has low price, high accuracy, satisfactory stability, very wide frequency response and long operation life, and therefore is well adapted to any voltage level up to 750 kV.     

新型HEWP智能互感器校验仪的研制

介绍新型智能互感器校验仪的设计思路及其特点和新功能。     

快速误差测试装置在互感器校验中的应用

分析了互感器误差快速测试的测量方法,使批量互感器的测试过程更加有效率。     

COD快速分析仪的开发和研制

根据纳米TiO2光催化原理，开发研制了一种以光度分析为检测手段的COD快速分析仅。本仪器检测时间短，消解时间在10min以内，操作简单，测量精密度高，能同时测定各类废水及地表水的COD值，且与标准法有良好的相关性．大大降低了对环境的二次污染，实现了对水体中COD值的快速分析。     

单片机控制油浸式变压器在线温度监测系统

针对变压器监测系统在实时性、可靠性方面的要求以及油浸式变压器发生故障时会产生不同的热效应,从而产生相应位置的异常温升的问题,讨论了基于嵌入式技术的大型变压器温度监测和故障诊断系统,详细地介绍了基于单片机控制的油浸式变压器温度采集电路的硬件电路设计。实践结果证明,该系统具有实时性强、可靠性高、运行成本低等优点,对大型油浸式变压器运行状态的实时温度监测和故障诊断而言,具有较广阔的应用前景。     

FIR modeling of voltage instrument transformers with iron core for the study of fast transients

Modern electronics found in various measuring equipment is sensitive to the effect of transient over-voltages. This paper treats the measurement procedure for the estimation of Finite Impulse Response (FIR) models of voltage instrument transformers, dedicated for the study of fast electromagnetic transients, with the special concern to its influence on the equipment connected to the secondary. A black-box approach is applied, and the model identification is based solely on a single measurement with the impulse excitation. The paper proposes two different procedures for the estimation of the analytical expression of the excitation, based on the parameters of the impulse generator or its estimation using a least-squares procedure. The frequency response of the transformer is used for the design of an initial FIR model, which was further reduced using corrected Akaike information criterion. This way the duration of the transient response calculation is further decreased, and the computation complexity reduced. Once determined, the FIR model allows, through the digital filtering operation (closely related to the concept of recursive convolution), a very easy time-domain calculation of the system’s response at any excitation.     

In-situ measurement of the current transformer burden in a current transformer testing system using a shunt resistor

Both the ratio error and phase angle error of a current transformer (CT) are significantly affected by the CT burden connected in series to the secondary terminal of the CT. Thus, the precise measurement of this CT burden is required for the evaluation of the CT errors. A method for measuring the CT burden in-situ in a CT testing system (CTTS) has been developed by employing the non-reactive type shunt resistor. For the measurement of the CT burden, the shunt resistor was connected in parallel to the secondary terminal of the CT under test in the CTTS. The burden values represented by the apparent power and the power factor can be calculated from the resistance (and reactance), which was obtained by measuring the ratio error (and phase angle error) as a function of the resistance of the shunt resistor. The uncertainties in the measurements of the apparent power and the power factor for the rated burdens studied were found to be less than 2.1%. The CT burden values obtained using our method were consistent with those measured using a digital multimeter within the corresponding uncertainties.     

电流互感器减极性和相量图常见疑惑辨析

从磁通势和感应电动势的角度阐述了电流互感器的减极性含义,绘制的电流互感器相量图消除了二次电流方向与实际工况明显相反的弊端。相关的概念、分析方法适用于电压互感器、变压器的原理分析。     

提高500kV大型变压器过载能力的研究

为解决500 kV大型变压器过载能力制约电网变电容量的问题,从技术角度探讨了变压器的过载能力承受范围,开展了变压器的过载理论分析,提出了包括环境温度、起始负荷、过负荷倍数、油温及热点温度等参数形成的核算边界条件,按照过载能力的核算模型校核变压器本体的过负荷能力,以尽可能释放其过载能力。研究结果表明:500 kV大容量变压器可按照环境温度35℃、起始负荷100%、过载倍数1.8倍、控制变压器油温100℃和绕组热点温度150℃,历时20 m in过载的原则进行生产及运行。