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

Kaczmarek, M.; Stano, Ernest

doi:10.1109/access.2020.3005331

Cited by 36 publications

(41 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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. Finally, in [11] it is demonstrated that the values of current and phase errors of transformation of the low order higher harmonics by inductive CT depends on the phase angle between transformed higher harmonics of the distorted primary current and the self-generated higher harmonics of the secondary current.…”

Section: Introductionmentioning

confidence: 97%

“…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%

See 1 more Smart Citation

Extended SINDICOMP: Characterizing MV Voltage Transformers with Sine Waves

et al. 2021

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Extended SINDICOMP: Characterizing MV Voltage Transformers with Sine Waves

et al. 2021

View full text Add to dashboard Cite

show abstract

“…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. In principle, they can be mitigated through a specific design of the CT [ 20 ] or by adopting signal processing techniques that enable significantly more accurate harmonic measurements.…”

Section: Introductionmentioning

confidence: 99%

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

Laurano

Toscani

Zanoni

2021

Sensors

View full text Add to dashboard Cite

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.

show abstract

“…The inductive instrument transformers are subject to many nonlinear effects causing problems in the accurate measurement of PQ issues [ 4 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. The rms values of the slow-front transient overvoltage in the secondary circuit of the inductive voltage transformer results from the internal resonance caused by the simultaneous presence of inductances and capacitances in the inductive voltage transformer (VT) [ 6 , 7 , 12 , 13 , 14 , 15 , 16 ]. In this paper the determined characteristic of voltage ratio error at harmonics with frequency for a given medium voltage inductive instrument transformer is used to predict the value of the slow-front overvoltage in its secondary circuit.…”

Section: Introductionmentioning

confidence: 99%

“…However, the resonance frequencies and the measured values of ratio error and phase displacement do not change with the value of the applied voltage. This is due to the fact that the transformation accuracy of the slow-front transient overvoltages results from the leakage inductances and the capacitances of windings [ 14 , 15 , 16 , 19 , 20 ]. It should be noted that at the rated voltage transient overvoltages are more likely to cause ferroresonance [ 13 ].…”

Section: Introductionmentioning

confidence: 99%

Transformation of Transient Overvoltages by Inductive Voltage Transformers

Kaczmarek

Brodecki

2021

Sensors

Self Cite

View full text Add to dashboard Cite

Overvoltage transients occur after any type of switching activity in a power network, such as breaker operation, fault occurrence/clearance and rapid load change. This distortion of voltage is transformed to the secondary circuit of a voltage transformer. The maximum values of such impulses may many times exceed the rated value of its secondary voltage. This can lead to malfunction of measuring or protection devices connected to the secondary circuit of a voltage transformer and even their damage. The paper presents the application of determined values of ratio error at harmonics of the inductive voltage of the transformer to predict the value of transformed slow-front transient overvoltage to their secondary circuits. This will help to prevent malfunction of measuring or protection devices connected to the secondary side of the voltage transformer and increase their safety of operation. The inductive voltage transformer equivalent circuit for transformation of higher frequency components of distorted voltage must be extended with internal capacitances of windings. This is caused by the fact that the resonance phenomenon of the slow-front transient overvoltage results from leakage inductance and capacitance of primary winding, not from the magnetic core. Therefore, this behaviour is independent from the value of the applied voltage.

show abstract

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

Cited by 36 publications

References 27 publications

Extended SINDICOMP: Characterizing MV Voltage Transformers with Sine Waves

Extended SINDICOMP: Characterizing MV Voltage Transformers with Sine Waves

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

Transformation of Transient Overvoltages by Inductive Voltage Transformers

Contact Info

Product

Resources

About