Compensation of nonlinearities in a current transformer for the reconstruction of the primary current

Bittanti, Sergio; Cuzzola, Francesco Alessandro; Lorito, F.; Poncia, G.

doi:10.1109/87.930967

Cited by 36 publications

(24 citation statements)

References 24 publications

(51 reference statements)

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“…CT nonlinear model is identified by means of a separable least squares method [10]. In this method primary current is estimated from distorted secondary current.…”

Section: Introductionmentioning

confidence: 99%

“…Different techniques and algorithms have been proposed by different authors to overcome CT saturation and its effect on DR performance [8]- [21]. The following drawbacks are observed in their methodologies or algorithms as they  Limits the use for either offline operation or online operation only [10,16]  Consider approximate nonlinear CT model [13]  Consider approximate values of some parameters like residual flux, winding impedance, inductive burden etc [9]  Suggest to increase size of CT to accommodate DC offset, which will make it bulky and expensive [19]  Suffer from magnetic fields produced by adjacent conductor [13]  Suffer from harmonics and noise [14]  Suffer from time delay and sensitivity [11] So to overcome the above issues altogether, it is suggested to choose an alternative to CT. Rogowski Coil (RC) has attracted much attention of electric power industry as it can meet the requirements of protective relaying due to its superior performance, inherent linearity, outstanding dynamic response, wide bandwidth and no magnetic saturation [22][23]. So far RC is used as current transducer in differential and over current protection.…”

Section: Introductionmentioning

confidence: 99%

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Use of Rogowski Coil as Current Transducer for Distance Relay Reach Correction

Sarwade¹,

Katti²,

Ghodekar³

2016

ijeei

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Conventional iron core CT gets saturated with increase in system X/R ratio, burden connected across it under normal condition and presence of DC component in symmetrical current waveform under faulty condition. CT saturation causes distance relay (DR) to under reach and operate it with certain time delay. The problem becomes more critical when fault takes place near to the boundary of first zone of DR. RC has become more popular for measurement of normal and complex transient current due to its inherent linearity, wide operating current range, reduced size, cost and its flexibility in operation. With the development of today's microprocessor/numerical relay, Rogowski coil (RC) has become more suitable for protective relaying applications. This paper presents use of RC for measurement of current in distance protection scheme (DPS). Case study for validation of use of RC is carried out on Electric furnace system. The simulation results of DPS used for protection of part of 220kV IEEE 9 Bus system shows excellent performance of RC over conventional CT during normal and abnormal conditions.

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“…CT nonlinear model is identified by means of a separable least squares method [10]. In this method primary current is estimated from distorted secondary current.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Use of Rogowski Coil as Current Transducer for Distance Relay Reach Correction

Sarwade¹,

Katti²,

Ghodekar³

2016

ijeei

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“…This means that th the surge current reaches its maximum is 8 point when it becomes half of the maximum is (8) where B is the magnetic flux density of the core, A denotes the magnetic vector potential of the winding region, and ± denotes the direction of the induced current in the two-dimensional analysis. …”

Section: Fourier Series Expansion For the Sumentioning

confidence: 99%

“…To express the surge current as a function, the amplitude of the frequency harmonics was extracted through the development of the 8/20 μs waveform of the standard surge wave as a Fourier series and its application to the surge analysis [3][4][5][6]. In the surge current analysis, 1,000 A and 5,000 A were applied as input currents to the primary winding of the CT before the magnetic core became saturated, and 50,000 A was also applied, at which point the magnetic core became saturated [7,8].…”

Section: Introductionmentioning

confidence: 99%

Magnetic Saturation Effect of the Iron Core in Current Transformers Under Lightning Flow

Kim¹

2017

Transactions on Electrical and Electronic Materials

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A current transformer (CT) is a type of sensor that consists of a combination of electric and magnetic circuits, and it measures large ac currents. When a large amount of current flows into the primary winding, the alternating magnetic flux in the iron core induces an electromotive force in the secondary winding. The characteristics of a CT are determined by the iron core design because the iron core is saturated above a certain magnetic flux density. In particular, when a large current, such as a current surge, is input into a CT, the iron core becomes saturated and the induced electromotive force in the secondary winding fluctuates severely. Under these conditions, the CT no longer functions as a sensor. In this study, the characteristics of the secondary winding were investigated using the timedifference finite element method when a current surge was provided as an input. The CT was modeled as a twodimensional analysis object using constraints, and the saturation characteristics of the iron core were evaluated using the Newton-Rhapson method. The results of the calculation were compared with the experimental data. The results of this study will prove useful in the designs of the iron core and the windings of CTs.

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“…A nonlinear analysis is conducted using the NewtonRaphson method to consider the characteristics of the magnetic saturation of the ferromagnetic core. [6][7][8] To express lightning surge as a function, an 8/20 [µs] surge waveform was expanded in a Fourier series to extract the magnitude of harmonics by frequency. This was applied to the surge analysis.…”

Section: Introductionmentioning

confidence: 99%

Electromotive force analysis of current transformer during lightning surge inflow using Fourier series expansion

Kim

2017

AIP Advances

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The most common structure used for current transformers (CTs) consists of secondary windings around a ferromagnetic core past the primary current being measured. A CT used as a surge protection device (SPD) may experience large inrushes of current, like surges. However, when a large current flows into the primary winding, measuring the magnitude of the current is difficult because the ferromagnetic core becomes magnetically saturated. Several approaches to reduce the saturation effect are described in the literature. A Rogowski coil is representative of several devices that measure large currents. It is an electrical device that measures alternating current (AC) or high-frequency current. However, such devices are very expensive in application. In addition, the volume of a CT must be increased to measure sufficiently large currents, but for installation spaces that are too small, other methods must be used. To solve this problem, it is necessary to analyze the magnetic field and electromotive force (EMF) characteristics when designing a CT. Thus, we proposed an analysis method for the CT under an inrush current using the time-domain finite element method (TDFEM). The input source current of a surge waveform is expanded by a Fourier series to obtain an instantaneous value. An FEM model of the device is derived in a two-dimensional system and coupled with EMF circuits. The time-derivative term in the differential equation is solved in each time step by the finite difference method. It is concluded that the proposed algorithm is useful for analyzing CT characteristics, including the field distribution. Consequently, the proposed algorithm yields a reference for obtaining the effects of design parameters and magnetic materials for special shapes and sizes before the CT is designed and manufactured.

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Compensation of nonlinearities in a current transformer for the reconstruction of the primary current

Cited by 36 publications

References 24 publications

Use of Rogowski Coil as Current Transducer for Distance Relay Reach Correction

Use of Rogowski Coil as Current Transducer for Distance Relay Reach Correction

Magnetic Saturation Effect of the Iron Core in Current Transformers Under Lightning Flow

Electromotive force analysis of current transformer during lightning surge inflow using Fourier series expansion

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