A Complex Current Ratio Device for the Calibration of Current Transformer Test Sets

Çaycı, H.

doi:10.2478/v10178-011-0015-2

Cited by 7 publications

(3 citation statements)

References 2 publications

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“…In the method described in [26] and [18], which has been mentioned in Section 2, an increment of simulated errors is limited to the discreteness of the PC-controlled three-phase power source, and a step of changing the ratio of turns of the electronically-compensated current comparator corresponds to 0.5 %. The use of a phase-shifting unit allowed the simulation of CT errors of almost any value using the method proposed.…”

Section: Discussionmentioning

confidence: 99%

Metrological characterisation of current transformers calibration unit for accurate measurement

Isaiev

Velychko

2021

ACTA IMEKO

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<p class="Abstract"><span lang="EN-US">The manuscript presents a method for the metrological characterisation of the commercial AC comparators used to calibrate current transformers. The theoretical basis for simulating the difference between two almost identical currents has been outlined, as well as the mathematical models for both a ratio error and a phase displacement has been derived. The measurement setup, consisting of conventional measuring instruments, has been described with a detailed presentation of its parameters. The sources of uncertainty have been distinguished and analysed with determining the current phase shift which led to a significant increase of relative measurement uncertainty. The simulation of measurement results was yielded in two ways: physically using a method presented and virtually using a Monte Carlo method. The second method confirmed that evaluating the measurement uncertainty through derived sensitivity coefficients is correct enough. The simulation results in the range from 1 to 1200 parts per million for both ratio error and phase displacement motivated the use of a comparator characterised through the proposed method for accurate measurement, especially for very low errors.</span></p>

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Section: Discussionmentioning

confidence: 99%

Metrological characterisation of current transformers calibration unit for accurate measurement

Isaiev

Velychko

2021

ACTA IMEKO

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“…To create a procedure for verifying the correctness of the readout of the comparison device, the metrologist must analyze the sources of uncertainty of such means [15][16][17]. Several methods for calibrating comparison devices have been developed [18][19][20][21][22][23], and all they have certain features. This chapter proposes methods for characterizing comparators of almost identical alternating currents or voltages to establish the metrological traceability when using such instruments for the calibration of CTs or VTs.…”

Section: Introductionmentioning

confidence: 99%

Methodological Aspects of Using Comparators for Metrological Traceability of Instrument Transformers

Isaiev¹,

Anokhin²

2022

Applied Aspects of Modern Metrology

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Instrument transformers are widely used in accounting the electricity as well as in protecting the energy generation systems. The accuracy of both voltage and current transformers is a critical parameter in terms of ensuring the reliability of functioning whether high-voltage or low-voltage networks. Two approaches are predominant in characterizing the voltage transformers with high primary rated voltage, these are applying either reference capacitor or reference transformer. Both methods require a device that enables the comparison of either two currents or two voltages. The errors of current transformers are determined by using the means of comparing two secondary currents, one of which is an output of reference transformer and the other is an output of a device under test. The calibration of such comparators may be a very sophisticated procedure. As metrological traceability depends on the measuring instruments and working standards used in calibration, the application of the proposed specific combinations of measuring instruments allows identifying the metrological traceability routes when calibrating the comparators.

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“…Conventional calibration methods generally use the electromagnetic CT with an iron core [5][6][7][8][9][10][11][12][13]. However, the iron core is easily saturated at high currents, unless a bulky iron core is used which encounters manufacturing difficulty.…”

Section: Introductionmentioning

confidence: 99%

A high-current calibration system based on indirect comparison of current transformer and Rogowski coil

Luo

et al. 2013

Meas. Sci. Technol.

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The calibration of the protective current transformer (CT) is of particular importance, since its accuracy at high currents is crucial to the correct operation of the subsequent relay protection devices. Conventional calibration methods have been using an electromagnetic CT which contains an iron core as the standard CT. The iron core is big and difficult to manufacture for high-current measurement, and the serious residual magnetism of the iron core at high currents can lead to excessive measurement errors. This paper proposes a calibration system based on indirect comparison of CT and Rogowski coil, i.e. using an iron-core CT to correct the error of the Rogowski coil at low currents, which may be caused by the position of the current-carrying conductor and so on, and then using the calibrated Rogowski coil as the standard transformer at high currents for its good linearity and wide dynamic range, and there is no magnetic saturation. Since the output of the Rogowski coil needs to be integrated, an improved digital integrator based on direct current (dc) negative feedback is adopted, which can effectively eliminate the influences of temperature drift, time drift and dc offset caused by the analogue circuit. The measurement errors of each part of the calibration system have also been discussed, and the test results show that the accuracy of the system can reach up to the 0.05S Class and the uncertainties are 0.038% for ratio and 0.68′ for phase in the range 500 A to 50 kA.

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A Complex Current Ratio Device for the Calibration of Current Transformer Test Sets

Cited by 7 publications

References 2 publications

Metrological characterisation of current transformers calibration unit for accurate measurement

Metrological characterisation of current transformers calibration unit for accurate measurement

Methodological Aspects of Using Comparators for Metrological Traceability of Instrument Transformers

A high-current calibration system based on indirect comparison of current transformer and Rogowski coil

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