A Novel Approach for the Error Correction of CT in the Presence of Harmonic Distortion

Ballal, Makarand Sudhakar; Wath, Manish Ganesh; Suryawanshi, Hiralal Murlidhar

doi:10.1109/tim.2018.2884575

Cited by 24 publications

(26 citation statements)

References 21 publications

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“…On the other hand, the impact of conventional CTs on harmonic measurements has been investigated by scientific papers for many years [ 12 , 13 , 14 , 15 ]; all of them agree that, in general, harmonic amplitudes and phases are transduced with considerably worse accuracy in comparison with the fundamental term. The main reason is often supposed to be the bandwidth limitation [ 16 ] due to the dynamics of the CT; techniques aimed at compensating its frequency response can be found in the literature [ 17 , 18 , 19 ]. However, (weak) nonlinearities are also present even when the core operates well below saturation [ 20 , 21 ]; their impact is significant as long as the measurement of low-order harmonics is concerned.…”

Section: Introductionmentioning

confidence: 99%

A Simple Method for Compensating Harmonic Distortion in Current Transformers: Experimental Validation

Laurano

Toscani

Zanoni

2021

Sensors

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Conventional current transformers (CTs) suffer from nonlinearities due to their ferromagnetic cores. On one hand, it is well-known that severe core saturation may occur because of large overcurrents or unidirectional transient components: this may substantially impact the operation of relays. On the other hand, weaker nonlinear effects are also present during regular working conditions. In particular, the spectral content of typical current waveforms is characterized by a strong fundamental term responsible for harmonic distortion affecting the frequency components at the secondary side. In turn, this has a significant impact on the accuracy that can be reached as long as current harmonics must be monitored. The target of this work is implementing a simple signal processing technique that allows compensating for this effect. The method, characterized by extremely low computational complexity, is first introduced and validated using numerical simulations. After this, it was tested experimentally to improve the harmonic measurement capability of inductive CTs. The achieved results highlight a noticeable reduction of errors at low-order harmonics over a wide range of primary current amplitudes. It is worth noting that the black-box approach makes the technique suitable also for compensating nonlinearities introduced by current transducers based on different operating principles. Thanks to this peculiarity and to the low computational complexity, the proposed method is suitable to be employed in power quality analyzers and merging units. In this way, high-accuracy monitoring of current harmonics in power systems can be achieved, opening the way to advanced power quality management and to the location of disturbing users.

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Section: Introductionmentioning

confidence: 99%

A Simple Method for Compensating Harmonic Distortion in Current Transformers: Experimental Validation

Laurano

Toscani

Zanoni

2021

Sensors

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“…The metrological performances of these sensors in presence of harmonic distortion significantly depend on their operating principles. In the particular case of the frequently used inductive instrument transformers (ITs), not negligible ratio and phase errors can be introduced both at low and high frequency harmonics [4][5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

“…In [5,6,8,9] the ITs characterizations performed under distorted conditions have highlighted errors up to some percent for the first 10-15 harmonics. In [10], some of the authors have shown that the current transformers (CTs) ratio and phase errors at power frequency can increase up to exceed their accuracy class limits in presence of modulated current signals.…”

Section: Introductionmentioning

confidence: 99%

Extended SINDICOMP: Characterizing MV Voltage Transformers with Sine Waves

et al. 2021

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The paper presents a method for the frequency characterization of voltage transformers (VTs) for medium voltage (MV) grids which involves only sine waves. It is called extended SINDICOMP, since it is an extended version of the previously developed technique SINDICOMP. It requires, in the first step, an evaluation and a compensation of the non-linearity introduced by the VT when it is supplied with a 50 Hz sinusoidal input at rated value. Then, the VT is characterized with a low voltage sinusoidal frequency sweep from the second harmonic frequency up to the first resonance frequency. Some rules to build the approximated frequency response, starting from these two sets of data, are given in the paper. The proposed approach is applied to three commercial MV VTs. Significant improvement of the VT performance is obtained, compared to the use of a frequency response obtained from the low voltage characterization.

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“…All mentioned external factors conditioning the rms values of the self-generated higher harmonics by the inductive CT into the secondary current must be considered to ensure effective compensation. None of the methods proposed in the papers [11][12][13][14][15] provides this. The nonlinear mathematical models can be used to compensate the measured value [16].…”

Section: Introductionmentioning

confidence: 99%

Nonlinearity of Magnetic Core in Evaluation of Current and Phase Errors of Transformation of Higher Harmonics of Distorted Current by Inductive Current Transformers

Kaczmarek

Stano

2020

IEEE Access

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The novelty of the paper contributes to the increase of the reliability of the methods used for evaluation of the inductive CTs accuracy of transformation of the distorted current. The results of performed analyses shows that the values of current and phase errors of transformation of the low order higher harmonics by inductive CT depends significantly from the phase angle between transformed higher harmonics of the distorted primary current and the self-generated higher harmonics of the secondary current. Moreover, higher harmonics of the distorted primary current may increase the peak value of the magnetic flux density in the magnetic core. Then the impact of the self-generated low order harmonics resulting from the nonlinearity of the magnetic core on values of current and phase errors of transformation of the higher harmonics of the distorted primary current is increased. Proposed evaluation procedure enables determination of the maximum values of current and phase errors of transformation of the higher harmonics of the distorted primary current. It is essential to determine the accuracy class. In such approach the impact of the secondary current's distortion caused by the nonlinearity of the magnetic core and the influence of the harmonic distortion on the peak value of the magnetic flux density are considered. Therefore, transformation accuracy of tested CT is ensured for specified range and type of the load of the secondary winding, rms values of primary current and its distortion. INDEX TERMS inductive current transformer, nonlinearity of magnetic core, transformation accuracy, distorted current, power quality, composite error, current and phase errors at harmonics.

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A Novel Approach for the Error Correction of CT in the Presence of Harmonic Distortion

Cited by 24 publications

References 21 publications

A Simple Method for Compensating Harmonic Distortion in Current Transformers: Experimental Validation

A Simple Method for Compensating Harmonic Distortion in Current Transformers: Experimental Validation

Extended SINDICOMP: Characterizing MV Voltage Transformers with Sine Waves

Nonlinearity of Magnetic Core in Evaluation of Current and Phase Errors of Transformation of Higher Harmonics of Distorted Current by Inductive Current Transformers

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