Wide-Band Two-Stage Current Transformers of High Accuracy

Souders, T. M.

doi:10.1109/tim.1972.4314039

Cited by 43 publications

(19 citation statements)

References 4 publications

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“…They are NIST built and calibrated using low temperature coefficient (TC) resistors and are compensated to have flat frequency response from dc to over 5 kHz and constant time delay over that frequency range. The three current transformers (CTs) are NIST built two stage [4] designs to give stable transimpedance and time delays over that same frequency range. The CTs have a ratio of 10 to 1.…”

Section: A Hardwarementioning

confidence: 99%

Calibration of Phasor Measurement Unit at NIST

Tang

Stenbakken²,

Goldstein

2013

IEEE Trans. Instrum. Meas.

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This paper describes the basic operating principles of Phasor Measurement Units (PMUs) and their time requirements to estimate absolute phase angles. A National Institute of Standards and Technology (NIST) PMU calibration system that tests PMU performance necessary to meet the IEEE synchrophasor standard requirements is discussed. The calibration of voltage, current, and time measurements for the NIST PMU test system is described. The total vector error of the NIST PMU test system is estimated to be 0.05%. A comparison between the NIST PMU test system and a prototype commercial PMU calibrator was performed to assure traceability of relevant electrical measurements and time measurement.Index Terms-Calibration, coordinated universal time (UTC), global positioning system (GPS), phase measurement unit (PMU), total vector error (TVE), traceability, uncertainty.

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Section: A Hardwarementioning

confidence: 99%

Calibration of Phasor Measurement Unit at NIST

Tang

Stenbakken²,

Goldstein

2013

IEEE Trans. Instrum. Meas.

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“…Amplifier Al is a current pump which performs the dual role of injecting the correct current into the input switch of A 2 irrespective of the switch resistance, and of providing a differential input. An amplifier-aided two-stage current transformer [5] provides accurate current scaling factors of 40: 1 and 400 : 1. The transformer secondary current is passed into a current-to-voltage converter comprising amplifier A 4 , a" VMOS transistor power booster, and the VMOS switch selectable gain resistors.…”

Section: Analog Signal Conditioningmentioning

confidence: 99%

Digital sampling laboratory wattmeter

Corney

Pullman

1987

IEEE Trans. Instrum. Meas.

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where Vi and I, are simultaneous samples of voltage and current equally spaced in time. It has been shown that, provided certain conditions are satisfied, (2) gives an ac- II. THE DIGITAL SAMPLING TECHNIQUEThe average power measured over an interval T is given by Abstract-A versatile laboratory multifunction wattmeter based on digital sampling has been developed for incorporation into a laboratory calibration system. The meter uses two IS-bit AID converters and achieves an overall power measurement accuracy of 0.015 percent of applied volt-amperes at mains frequencies over. the range 100 rnA to 100 A and 5-100 V. Although intended for system use through the IEEE 488 bus, the meter can be used as a stand-alone instrument if required. curate result for relatively few samples [2]. Furthermore, the samples need not be taken over a single period but can be spread over m periods (where m is an integer) allowing the sampling interval to be increased accordingly. The conditions required are: 1) the sampling must occur over an integral number of waveforms; and 2) the waveform is stationary for the duration of measurement.With these two conditions satisfied the result is accurate for all power harmonics except; those harmonics k, for which km / n is an integer. The harmonic power terms arise from harmonics V p and I q in the voltage and current waveforms combining to produce power components at the (p + q )th and (p -q )th harmonics. Therefore if m and n have no factors in common, errors are limited to those voltage-current products where p + q or p -q is an integral multiple of n, the number of samples taken.Hence, for low values of n, errors may not be negligible particularly if both waveforms are nonsinusoidal or if a dc component is present on one waveform while the other contains significant distortion. Nevertheless the technique promises high accuracy for waveforms which are essentially sinusoidal, and it is under these conditions that the power calibration standard is used. III . WATTMETER CONFIGURATIONThe basic configuration of the digital sampling wattmeter is shown in Fig. 1. The instrument is controlled by an 8085-based single-board computer which is multibus compatible. Signal conditioning boards for current and voltage are placed in a separately screened compartment to shield against the noise generated by the processor board. These boards comprise a selectable gain voltage amplifier and current-to-voltage converter for the voltage and current signals, respectively. The gains are automatically switched by the processor so that the output signal levels are as close as possible to, but do not exceed, the ± 5-V input range of the analog-to-digital converters. The digitization is performed by two IS-bit hybrid converters which are simultaneously triggered at a sampling interval previously determined by the processor. The samples from each converter are multiplied together and the products are summed and then averaged to obtain the power measurement. During data acquisition and subsequent processing, checks are mad...

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“…In this kind of transformers, the main error source is the magnetizing currents, and many methods to reduce its influence have been proposed. Some of them are based on double cores and double windings [1] and others on electronic compensating devices [2]- [3]. The second source of errors is parasitic capacitance.…”

Section: Introductionmentioning

confidence: 99%

A self-calibrating high-precision current transformer

Slomovitz¹,

Castet²

2008

2008 Conference on Precision Electromagnetic Measurements Digest

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A self-calibrating current transformer with nominal ratio 10 A to 100 mA, intended for low frequencies applications, was developed. It has 100 independent primary windings to be connected in series or parallel, so that it can be configured as 100:1 or 1:1 transformer (all windings in series). This last ratio permits autocalibration. Error sources are analyzed, and it is shown that differences between parallel and series configurations have uncertainties lower than 1 part in 10 6 .

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Wide-Band Two-Stage Current Transformers of High Accuracy

Cited by 43 publications

References 4 publications

Calibration of Phasor Measurement Unit at NIST

Calibration of Phasor Measurement Unit at NIST

Digital sampling laboratory wattmeter

A self-calibrating high-precision current transformer

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