Damir Ilić

Mutual Inductance of a Precise Rogowski Coil in Dependence of the Position of Primary Conductor

The Rogowski coil is a well-known current-to-voltage transducer. To use it for the high-accuracy measurement of AC current (at power supply frequency), all influencing quantities and their contribution should be recognized and analyzed. Thus, the partial influence due to the deviation from the central position of the primary conductor for a real sensor, with the nonhomogeneous density of secondary turns, is given in this paper. The measured deviation of mutual inductance in this case showed very good agreement with the theoretical prediction, which is promising for the expected application of such a sensor.

Realization of the kilogram by measuring at 100 kV with the voltage balance ETF

The possibilities for adapting the existing electrostatic device known as the voltage balance ETF-84, to work with a voltage of 100 kV and a weight of 1 kg, are considered. A few theoretical analyses, experiments, and computer simulations have been carried out to define the measurement procedure needed at the required level of uncertainty of 1 part in 10/sup 8/. These analyses identified which parts of the balance itself and of the high voltage electrode isolation have to be reconstructed, as well as how the associated high voltage resistor has to be designed for this purpose.

Analysis of the mutual inductance of a precise Rogowski coil

A Rogowski coil is well-known current-to-voltage transducer, and in order to use it for the high-accuracy measurement of AC current (at power supply frequency) all influencing quantities and their contribution should be recognized and analyzed. Therefore, in this paper the analysis of the partial influence due to the deviation from the central position of the primary conductor for a real sensor, with the nonhomogeneous density of secondary turns is analyzed. The measured deviation of the mutual inductance in this case showed very good agreement with the theoretical prediction, which is promising toward the expected application of such sensor.

Determination of High-Resolution Digital Voltmeter Input Parameters

High-resolution digital voltmeters (DVMs) can be widely used when precise measurements are needed, but input circuitry can contribute to the results of measurement. Therefore, to make uncertainty of measurement as small as possible for a particular measurement, it is necessary to characterize its input parameters. In this paper, the methods for the determination of input resistance, input capacitance, and input offset current of widely used precise DVMs HP 3458A with 8 1/2-digit resolution are presented. The method with voltage source and high-ohmic divider resistor has been developed for the determination of both input offset current IS and input resistance RV. The second method with the source of the linear voltage ramp and the picoampermeter is primarily used for the determination of input capacitance CV. It was shown that the input offset current of voltmeters is in the range of picoamperes with relative instability of approximately plusmn0.1, the input resistance is in the range of teraohms with the same relative instability of plusmn0.1, and the input capacitance was measured to be in the range of a few hundred picofarads with uncertainty of a few picofarads.

The basis of Croatian electromagnetic metrology

Measuring equipment, standards, methods and procedures necessary to ensure the traceability in the laboratory calibration system of electromagnetic quantities, are described. The accuracy scale and appropriate uncertainties appearing at the specific levels when measuring electric quantities such as voltage, current, power, resistance, capacitance etc., are analyzed. The research directions and possibilities of the international and national interlaboratory connections, are discussed.

Influence of Axial Inclination of the Primary Conductor on Mutual Inductance of a Precise Rogowski Coil

In order to use a Rogowski coil for high-accuracy measurement of ac current (up to 20 A at power supply frequency, with an aimed uncertainty of 100 ppm), all influencing quantities and their contributions should be recognized and analyzed. The same theoretical basis can be applied if the use of such a transducer is planned for much higher currents and/or frequencies. Therefore, this paper gives the analysis of the partial influence due to the angle of the primary conductor relative to the secondary coil, with nonhomogeneous density of secondary turns. The measured deviation of mutual inductance showed agreement with the results of theoretical considerations, which show that careful construction of this sensor can provide the required accuracy.

Use of precise digital voltmeters for ac voltage measurements

The possibility of using high-resolution digital voltmeters for ac voltage measurements at a frequency of about 16 Hz is presented. The method for the determination of correction factors in phase difference measurements with two synchronised voltmeters is described, and a level of uncertainty of 0,1 /spl mu/rad is achieved.

An accurate calculation of the reference electric field nonuniformity

Computer-aided calculation of the reference electric field nonuniformity in the electric field-meter calibration system is presented, which can help to lower the uncertainty of the reference field generation, and to reduce the traditionally large size of calibration systems.

Nonparametric Estimation of the Phase Difference Using RV1 and MSL Windows

This paper describes the measurement and nonparametric estimation of phase difference with stronger inhibition of spectral leakage. The phase difference is estimated by discrete Fourier transform coefficients around component peaks using Rife-Vincent windows class I (RV1) and the minimum side-lobe level (MSL) windows. Selecting a suitable window order, MSL windows demonstrate a very low bias error and lower noise error propagation than RV1 windows. A practical example evaluates the accuracy of the used windows in estimations.

A concept for experimental testing of oil-barrier insulation system

The aim of this paper is to present a concept for experimental testing of transformer oil-barrier insulation system. Design of insulation model is proposed with the purpose to avoid typical problems reported in literature concerning partial discharge testing of paper coated electrodes. Electric field between model electrodes is analyzed with methods commonly used in transformer insulation design - cumulative method and maximum electric field method. Model prototype is produced and tested to confirm functionality of the proposed concept. Also, model uncertainty is estimated to define model geometry influence on the test results