Instrument transformers: A different approach to their modeling

Torre, F. Della; Faifer, Marco; Morando, A.P.; Ottoboni, R.; Cherbaucich, C.; Gentili, M.; Mazza, Paolo

doi:10.1109/amps.2011.6090433

Cited by 15 publications

(12 citation statements)

References 8 publications

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“…In the literature, this is confirmed by many publications. For example, models for ITs, and, in particular, for CTs and voltage transformers (VTs), are developed in [ 33 , 34 , 35 ] respectively. As for LPITs, they have been modeled in [ 36 , 37 ] for LPVTs and Rogowski coils, respectively.…”

Section: Importance Of Testingmentioning

confidence: 99%

Accuracy Type Test for Rogowski Coils Subjected to Distorted Signals, Temperature, Humidity, and Position Variations

Mingotti

Costa

Peretto

et al. 2022

Sensors

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Low-Power Instrument Transformers (LPITs) are becoming the first choice for distributed measurement systems for medium voltage networks. However, there are still a lot of challenges related to their operation. Such challenges include their accuracy variation when several influence quantities are acting on them. Among the most significant influence quantities are temperature, electromagnetic field, humidity, etc. Another aspect that increases the importance of studying the LPITs’ accuracy behavior is that, once installed, they cannot be calibrated for several years; hence, one cannot compensate for in-field conditions. Hence, this work aims at introducing a simple type test for a specific LPIT, the Rogowski coil. First, an experimental setup to assess the effect of temperature, humidity, and positioning on the power quality accuracy performance of the Rogowski coil is described. Second, from the results and the experience of the authors it has been possible to design a specific type test. The test has the aim of finding the limits of the accuracy variations of a single Rogowski coil. Afterwards, such limits can be used to compensate for the in-field measurements, obtaining an overall higher accuracy. The results of this work may contribute to the always-evolving standardization work on LPITs.

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Section: Importance Of Testingmentioning

confidence: 99%

Accuracy Type Test for Rogowski Coils Subjected to Distorted Signals, Temperature, Humidity, and Position Variations

Mingotti

Costa

Peretto

et al. 2022

Sensors

View full text Add to dashboard Cite

show abstract

“…However, the equivalent circuit with constant parameters does not consider a number of phenomena related to saturation and the mechanism of the occurrence of core losses. For this reason, there are several publications that introduce some improvements to this scheme; above all, these publications allow the approximate saturation effect and hysteresis to be considered [3]. In addition, many works were related to the transformation problem for waveforms that were distorted and with a frequency higher than 50 Hz [4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Analysis of the Operation of Cascade Current Transformers for Measurements of Short-Circuit Currents with a Non-Periodic Component with a Large Time Constant of Its Decay

Leśniewska

Olak

2022

Energies

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Simulations of emergency states and tests of resistance of electrical devices to emergencies are performed in specialized high-power laboratories, the so-called short-circuit laboratories. For most electrical power devices, such measurements are required by international standards. The basic equipment of short-circuit testing laboratories consists of current transformers for measuring short-circuit currents. These transformers should not only enable the accurate conversion of sinusoidal currents—which is typical for conventional current transformers, but also asymmetrical short-circuit currents containing an aperiodic component, which classic current transformers cannot reproduce. Therefore, manufacturers and designers try to meet the market demands and design these special class 0.2 current transformers. To meet the high technical requirements, the field-circuit method with three-dimensional space–time analysis of electromagnetic fields was used during design, considering physical phenomena in ferromagnetic cores (i.e., hysteresis and eddy current losses) and the load of the secondary winding of the current transformer by the measurement system. The article presents simulations of secondary currents for the short-circuit current transformer model, and the results were confirmed by measurements and oscillograms of the currents flowing in the windings of the real model. The prototype of the designed short-circuit transformer meets the IEC/EN standard requirements. When measuring harmonic currents, the transformation errors meet the requirements of class 0.2. During the short-circuit current waveforms, the maximum instantaneous peak error does not exceed 1% of the error for all the subsequent maxima of the current waveform during the specified transient switching cycle. In comparison, the standard allows this error to be 10%.

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“…The model, based on a lumped parameters circuital approximation, is designed for solid insulation VTs, which are often installed in MV distribution grid applications (1 kV to 36 kV). Differently from other proposed VT models, [11]- [13], the presented one is based on a quite simple integrated numerical/experimental approach, which allows to reconstruct the VT performances from the 2 nd harmonic up to the first resonance frequency. In addition, the experimental tests conditions are chosen so that the VT core operates under rated magnetized conditions.…”

Section: Introductionmentioning

confidence: 99%

Stray Parameter Evaluation of Voltage Transformers for PQ Measurement in MV Applications

Giordano

Crotti

Letizia

et al. 2022

2022 20th International Conference on Harmonics &Amp; Quality of Power (ICHQP)

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Power Quality (PQ) monitoring is one of the key tasks in modern power systems. In transmission and distribution grids, PQ phenomena are often measured by inductive Voltage Transformers (VTs) installed for metering and/or protection applications. VTs accuracy requirements should be ideally met under actual operating conditions, which can differ from the calibration ones, in particular for the presence of environmental or circuital influence factors. The impact of such influence factors on the VT performance in PQ measurements is an open issue, not fully addressed in the literature. In this respect, this paper presents a simplified numerical-experimental model of inductive MV VTs, which can be used for the analysis of VT wideband behaviour in PQ applications, also in presence of one or more influence factors. The results provided by the model are experimentally validated and future applications are discussed.

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Instrument transformers: A different approach to their modeling

Cited by 15 publications

References 8 publications

Accuracy Type Test for Rogowski Coils Subjected to Distorted Signals, Temperature, Humidity, and Position Variations

Accuracy Type Test for Rogowski Coils Subjected to Distorted Signals, Temperature, Humidity, and Position Variations

Analysis of the Operation of Cascade Current Transformers for Measurements of Short-Circuit Currents with a Non-Periodic Component with a Large Time Constant of Its Decay

Stray Parameter Evaluation of Voltage Transformers for PQ Measurement in MV Applications

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