Are Inductive Current Transformers Performance Really Affected by Actual Distorted Network Conditions? An Experimental Case Study

Mingotti, Alessandro; Peretto, Lorenzo; Bartolomei, Lorenzo; Cavaliere, Diego; Tinarelli, Roberto

doi:10.3390/s20030927

Cited by 23 publications

(15 citation statements)

References 39 publications

(10 reference statements)

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“…A notable feature is that, according to this representation, the behavior at the fundamental component is not affected by the presence of other harmonics in the primary current. This peculiarity is often exploited during the study of conventional instrument transformers; it is confirmed by the experimental results presented in many works and specifically addressed by [32]. (6) can be rewritten as:…”

Section: Hd Compensation Techniquementioning

confidence: 59%

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: Hd Compensation Techniquementioning

confidence: 59%

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

Laurano

Toscani

Zanoni

2021

Sensors

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“…However, there is an opposite opinion. In particular, in [7], by reproducing the real current curves through the transformer and estimating the total error, it was found that the non-sinusoidal current has an insignificant effect on the measurement accuracy (the error did not exceed the allowable one for the accuracy class). Temperature and magnetic properties of the core are also indicated as essential factors [8].…”

Section: Literature Review and Problem Statementmentioning

confidence: 99%

Determining the static characteristic of a measuring current transformer at a reduced load of the metering unit

Vasylets

Kvasnikov

Vasylets

2022

EEJET

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The object of the research is a measuring current transformer of the electromagnetic type, which is used as part of the electricity metering unit. The current transformers functioning in the mode of reduced primary current is accompanied by significant errors. The existence of such a regime for a long time due to downtime of production equipment leads to a significant underestimation of electricity. This leads to unjustified financial losses for energy supply companies as electricity in many countries has become more expensive. The static characteristic of the measuring current transformer at a reduced load of the metering unit is described by a linear statistical model. The parameters of the model are estimated on the basis of empirical data using methods of covariance analysis. The adequacy of the model is confirmed by analysis of regression residuals. The obtained statistical model of the static characteristic, unlike the known ones, is characterized by universality, as it describes current transformers with an arbitrary transformation ratio within the studied accuracy class of 0.5S. The uncertainty of the current error is estimated using the prediction intervals for the transformers secondary currents as a function of the primary currents, calculated on the basis of the obtained model. The prediction intervals for sample values of the current error were obtained through the application of the proposed approach for uncertainty estimation of such an error at a reduced load of the metering unit. It was found that the current error can reach −20 %. Taking into account the indicated intervals for measuring current transformers at a reduced load of the metering unit during billing will allow energy supply companies to increase the accuracy of commercial electricity metering.

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“…It should be emphasized that due to the non-linear shape of the magnetizing characteristic of the magnetic core, the transformation accuracy of the inductive CT depends on the value of the magnetic flux density and thus on the RMS values of the primary current harmonics and the load on the secondary winding [1], [3], [4], [19], [23]. The paper [5] presents analyses on the transformation accuracy of inductive CTs under real operating conditions in a distribution grid. According to the authors, the distortion of the primary current has little influence on their values of current error and phase displacement and may be neglected.…”

Section: Introductionmentioning

confidence: 99%

The Influence of the 3rd Harmonic of the Distorted Primary Current on the Self-Generation of the Inductive Current Transformers

Kaczmarek

Stano

2022

IEEE Access

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This paper investigates for transformation of the distorted current the low order higher harmonic self-generation phenomenon of tested inductive current transformers. The influence of the main component and the 3rd harmonic of the distorted primary current on the RMS values of the 5th, 7th and 9th order self-generated higher harmonics is analyzed. This research indicate that the change of the RMS value of the 3rd harmonic of the distorted primary current causes variation of the lower order higher harmonics generated in to the secondary current. Therefore, this is a challenging phenomenon which have to be considered while compensating the values of current error and phase displacement of the inductive CTs during transformation of the distorted currents.INDEX TERMS self-generation, distorted primary current, inductive current transformer, low order higher harmonics, current error, phase displacement.

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Are Inductive Current Transformers Performance Really Affected by Actual Distorted Network Conditions? An Experimental Case Study

Cited by 23 publications

References 39 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

Determining the static characteristic of a measuring current transformer at a reduced load of the metering unit

The Influence of the 3rd Harmonic of the Distorted Primary Current on the Self-Generation of the Inductive Current Transformers

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