电子式电流互感器校验方法研究

提出一种校验电子式电流互感器模拟量输出和数字量输出的方法,该方法基于采样测量技术,测量标准电流互感器和被校电子式电流互感器的二次输出,比较二者的差异得到被校电子式电流互感器的比值误差和相位误差。详细分析了电子式电流互感器模拟量输出及数字量输出校验方法的测量误差,论证了该方法的合理性和可行性。根据该方法研制的校验装置样机在国家高电压计量站进行了校准测试,测试结果表明,所研制的校验装置满足校验0.2及以下等级计量用电子式电流互感器的准确度要求。     

High Accuracy On-Line Calibration System for Current Transformers Based on Clamp-Shape Rogowski Coil and Improved Digital Integrator

To solve the problems of the existing on-site calibration methods, for instance, the methods need power off, and the standard transformers have large volume, heavy weight and small dynamic range, this paper proposes a high accuracy on-line calibration method for current transformers. By using a clamp-shape Rogowski coil as the standard current transformer, instead of traditional electromagnetic transformer, the volume and weight are reduced greatly, and the power of the line needn’t to be interrupted. The output signal of the clamp-shape Rogowski coil needs to be integrated, and to overcome the problems of analog integrator, which have temperature and zero drift, a high accuracy digital integrator is proposed in the paper to improve the accuracy and stability of the signal processing circuit. Test results indicate that the accuracy of the whole calibration system can reach up to 0.05 accuracy class. The on-line calibration system can calibrate the traditional and electronic current transformers when the line is energized.     

基于改进型两次平衡对检法的感应分压器自校准方法

介绍了参考电势变压器和指零仪变压器设计原理,分析了屏蔽间泄漏对测量结果的影响;对常规两次平衡参考电势对检法进行了改进,使零平衡和段平衡测量过程中,参考电势和测差电路均可实现等电位保护;对自校准方法进行了推导,校准结果仅与段平衡和零平衡时锁相放大器测量的电压差值相关,与参考电势变压器、指零仪变压器、辅助变压器等的误差无关,屏蔽间泄漏的影响也得到消除。对1kV感应分压器进行了校准实验,并对校准结果进行了测量不确定度分析,其相对扩展不确定度的评估结果为5.4×10^-8(k=2)。     

Calibration of Voltage Transformers and High- Voltage Capacitors at NIST

The National Institute of Standards and Technology (NIST) calibration service for voltage transformers and high-voltage capacitors is described. The service for voltage transformers provides measurements of ratio correction factors and phase angles at primary voltages up to 170 kV and secondary voltages as low as 10 V at 60 Hz. Calibrations at frequencies from 50–400 Hz are available over a more limited voltage range. The service for high-voltage capacitors provides measurements of capacitance and dissipation factor at applied voltages ranging from 100 V to 170 kV at 60 Hz depending on the nominal capacitance. Calibrations over a reduced voltage range at other frequencies are also available. As in the case with voltage transformers, these voltage constraints are determined by the facilities at NIST.     

电子式互感器校验仪校验方法的研究

电子式互感器在电网中的应用越来越多,对电子式互感器准确度校准所使用的电子式互感器校验仪变得更加重要。电子式互感器校验仪采用直接测量法对电子式互感器进行校准,可以对模拟量输出和数字量输出的电子式互感器进行准确度校准,也可以对传统的电磁式互感器进行校准。为了保证电子式互感器校验仪的准确性,文中对电子式互感器校验仪的校准方法进行了深入的研究。针对电子式互感器校验仪的特点,分别对采样通道的采样准确度、比差、角差等进行了校验。     

高电压脉冲校准装置研究

为解决高电压脉冲的校准问题,对高电压脉冲的校准方法进行研究,并建立了一套脉冲校准装置。校准装置将高电压脉冲信号进行电压转换,变为脉冲小电压,通过数据采集系统,在频带范围10Hz~1kHz、电压范围1~1600V内,对脉冲电压的关键参数进行测量,得到高电压脉冲的电压幅度、脉冲频率、脉冲宽度、上升时间和下降时间。通过实验室标准仪器设备对高电压脉冲校准装置进行测试,其中脉冲幅度的测量误差为 0.02%~0.4%。     

Automation and Evaluation of Two Different Techniques to Calibrate Precision Calibrators for Low Frequency Voltage Using Thermal Devices

Low frequency (LF) voltage and current are important parameters in electrical metrology. The standards for LF voltage and current are established by assigning AC–DC transfer difference to thermal devices, i.e. thermal converters or thermal transfer standard along with current shunts. Automated calibration systems have been developed based on Null method and measurement technique developed by Budovsky for calibration of precision calibrator in LF voltage and current against thermal devices. The technique based on the Algorithm developed by Dr. Ilya Budovsky (National Metrology Institute (NMI), Australia) has been compared with the conventional null technique. Indigenously developed software has been used to calibrate the precision calibrator in the entire LF voltage and current range using Holt thermal converters and current shunts. Calibration results at 1 V, 10 V in the frequency range from 10 Hz to 1 MHz as well as calibration results of 1 A in the frequency range from 40 Hz to 10 kHz are presented in this paper. These result shows that the measurement technique developed by Budovsky has reduced the complexity of AC–DC transfer measurements, measurement time and the uncertainty in measurement.     

A wide-band active current transformer and shunt

An active current transformer and shunt with high accuracy and wide frequency range is described. The transformer, which uses two three-stage core transformers with two two-stage feedback amplifiers, can be used in the audio frequency band. It has a wide range of current ratio (0.01-1) and can dissipate 10 W in the external burden. If the external burden of the transformer is an AC standard resistor, it becomes an AC current to voltage transducer that can be used in many electrical measurements. The relative uncertainty (3σ) in the current ratio of the new transformer is between (1+j1) p.p.m. to (8+j8) p.p.m. over the frequency range from 40 Hz to 10 kHz     

A Study on Measurement Error during Alternating Current Induced Voltage Tests on Large Transformers

1IntroductionIn a resistance, inductance, and capacitance series circuit, the voltage across the capacitance canbe greater than the source voltage due to the compensative effect of the inductance. This phenome-non, referred to as the capacitive rise, has been fully studied and favorably employed in electricaland electronic systems, but has not been paid much attention in high voltage tests.To guarantee safe and reliable operation, transformers of220 kVand above are recommended in IEC(Interna…     

电磁式电压互感器谐波误差测量方法研究

为实现电磁式电压互感器在基波叠加谐波的实际波形下的计量误差测试,提出一种基于有源电子分压器的测量电磁式电压互感器谐波计量特性测量方法。以有源电容式分压器作为宽频比例标准装置,采用误差反馈技术,提高互感器二次转换单元测量准确度,基于LabVIEW和高精度数字化仪完成信号的测量和误差的计算,完成对4台电磁式电压互感器进行谐波计量特性测试。测试结果表明:随着谐波次数升高,在互感器的自身电感与分布电容的谐振处,误差急剧变化;二次负荷功率因数为0.8时,会对电压互感器的误差起到一定补偿作用,被试10 kV互感器在50-1500 Hz范围内,35 kV电压互感器在50-1000 Hz范围内,可满足电能质量监测要求。但从电能计量的角度出发,两者在50-2500 Hz范围内测量误差可满足要求。     

An Online Calibration Method for Electronic Voltage Transformers Based on IEC 61850-9-2

Since electronic voltage transformers (EVTs) based on IEC 61850-9-2 are widely used in the substations, especially in the automating substations, their calibration becomes very important. Generally, the calibration of EVTs needs for the power to be interrupted and causes power outage, and also the faults of the running transformers cannot be found in time. For this reason, an online calibration system is proposed in this paper. By employing a specially designed remote-controlled hoisting unit and standard voltage transformer, the proposed system can calibrate EVTs without interrupting the power service and the power outage can be avoided. A two-order Hanning self-convolution window algorithm is adopted to suppress the influence of spectrum leakage caused by frequency fluctuation and harmonic interference. Tests have been performed in the China Electric Power Research Institute. The results show that the proposed system has good performance and it can reach the accuracy class of 0.05 in complicated electromagnetic fields.     

Application of a standard two-stage transformer for checking purposes

Conclusions A standard two-stage current transformer at a frequency of 50 Hz when operating with domestic differential-null comparison instrument is not less accurate than three-winding magnetic current comparators and is superior to them in its speed of measurement and portability. For a simple and economic modernization of the standard measuring facilities employed in the USSR to check commercial-frequency current transformers the three-winding magnetic current comparators and uncompensated transformers should be replaced by standard two-stage current transformers.Translated from Izmeritel'naya Tekhnika, No. 5, pp. 65–67, May, 1980.     

一种中频双级电子式电流互感器误差特性的研究

研究了一种基于低功率铁心线圈的中频双级电子式电流互感器.通过对中频双级电子式电流互感器等效电路的分析,得到了电流误差和相位误差的表达式.为验证双级电子式电流互感器的中频传感性能,构建了基于差值法的中频双级电子式电流互感器校验系统,该系统采用32位DSP浮点芯片TMS320F28335进行数据采集控制和运算处理.实验结果表明,该双级电子式电流互感器在50～1 000Hz频率范围内的误差准确度可达0.05级.     

DC reactor type transformer inrush current limiter

A new inrush current limiter (ICL) is presented to limit the inrush current of transformers. The proposed ICL consists of three similar sets. Each set includes a diode-bridge and a single DC reactor and is connected in series with the individual phases of transformer. The ICL has almost no effect on normal operation of transformer. It needs no control, measurement and gate driving system and has a simple power circuit topology. The equivalent instantaneous inductance of transformer is used for analysis of circuit operation. The theoretical analysis, design features, power losses and voltage distortion because of using ICL are presented. The proposed method has been tested by simulation and laboratory experiments. Both results show that the proposed ICL successfully limits the inrush current.     

基于电压电流比的瞬态电磁流量测量方法

为了实现较高的励磁频率,提高响应速度,同时减少电磁流量计的功耗,提出基于电压电流比值的瞬态测量方法,确定电压电流比值与流量之间的关系。设计了基于DSP的硬件,采集瞬态时的励磁电流和信号电压来验证该处理方法,离线数据分析表明,电压电流比值与流量有良好的线性关系。设计的DSP软件可实时实现瞬态测量方法,并进行水流量标定和功耗测试实验。实验结果表明,流量测量准确度达到0.5级,与普通电磁流量计相同。功耗对比表明,基于瞬态测量原理的电磁流量计的励磁功耗是普通电磁流量计的30%。     

A highly accurate, hand-held clamp-on current transformer

The design, operation, and performance of a 1000:5 A highly accurate, hand-held, clamp-on-type current transformer are presented. This precision current transformer uses a sensitive magnetic circuit to detect transformer ampere-turn unbalance between the primary and secondary circuits. The unbalance represents an error in the ratio and phase angle of the transformer. The largest of the errors is due to the core magnetization current and magnetic reluctance caused by the cutting of the core material. After sensing the errors, electronic feedback through a magnetic circuit is used to provide an error-correcting current. This reduces the overall errors dramatically. These types of devices are referred to as “active” current transformers because of the use of electronic amplifier and feedback circuits. The device described has a novel feature of an openable, split core. This “clamp-on” capability enables use of the transformer on a bus or cable without the complications or need to open the current-carrying circuit to be measured. Commonly used “clamp-on”-type current transformers generally have uncertainties from about 1 to 5% at full-scale rated current. This paper describes a commercialization of active current transformers having a ratio uncertainty of less than ±0.05% over a current range from full-scale rated to 1% of full-scale. Additionally, this product has a small phase angle which is an important consideration when measuring electric power, energy, and power factor. It is intended to be used by electric utilities, standards laboratories, testing laboratories, and in applications where high measurement accuracy and the split-core, clamp-on feature are attractive considerations     

Power comparator based on-site calibration of isolating current transformers

A portable system for on-site calibrations of isolating current transformers in stationary energy meter test systems is described. The uncertainties of the calibration system are in the order of 0.005 % for the ratio error and 0.01 crad for the phase displacement of the current transformer at power frequencies. The power comparator based measurements can be done at test currents from 50 mA to 120 A.     

The Precise Measurement of Current Ratios

The development of the current comparator, a three-winding current ratio transformer, is reviewed and its characteristics as an alternating current ratio standard are analyzed. Particular attention is given to the use of magnetic shielding and its effect on the accuracy and usefulness of the device. Some error characteristics of three types of audio-frequency current comparators are given and possible applications discussed. These include the calibration of current transformers and impedance comparisons. The adaptation of this device to dc operation is made possible by modulation techniques. A 20 000-ampere self-balancing direct current comparator, designed specifically for the calibration in situ of transductors or direct current transformers, is described. The application of this comparator to the calibration of shunts at high currents also is discussed and some results presented.     

测量用互感器及其测试仪器的发展和创新

详细分析了国内50年代以来,随着生产发展和市场需要,测量用互感器及其测试仪器在提高准确度和性能方面的发展与创新概况。其中主要有：互感器误差补偿的研究和创新,并据此研制各种规格的测量用互感器、带升流器或升压器的高准确度互感器、电流比较仪、双级互感器、比较仪式互感器校验仪及其整体检定装置和数显校验仪等。并展望今后在这方面的发展和创新,如二次为小电流和小电压的互感器以及计算机在互感器及其测试中的应用等。