Investigations of transformer winding responses to standard full and chopped lightning impulses

Florkowski, Marek; Furgał, J.; Kuniewski, Maciej; Pająk, P.

doi:10.1109/ichve.2018.8641844

Cited by 3 publications

(12 citation statements)

References 8 publications

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“…Hence, univariate analysis is not reliable for identification of fault since there are many signals are involved during testing of transformers as per the specified standards [8, 9, 14–18 ]. The univariate analysis alone is not sufficient to analyse the behaviour of multiple signals, therefore bivariate or multivariate analysis are necessary for impulse testing of transformers at manufacturing place [6–16, 18, 19 ].…”

Section: Principles Of Fault Detection During Impulse Testingmentioning

confidence: 99%

“…During the impulse test, the rated impulse test voltage is applied in each phase of a transformer (one at a time). The applied standard impulse waveshape will propagate along with the tested HV terminal of the winding, and it will reach a neutral terminal [1,2,7,[9][10][11][12][13][14][15][16]. Therefore, winding response (ground current) is measured by using the current shunt at a neutral terminal [1][2][3][4][5].…”

Section: Measurement Of Impulse Winding Responses On Transformersmentioning

confidence: 99%

“…The digital signal measurement will permit the testing engineer to analyse the signal processing tools into data analysis about transformer failure (breakdown, PD etc.,) than visual inspections in the digital storage oscillographic traces [7][8][9][10][11][12][13][14][15][16][17][18][19]. The digital signal measurement of standard impulse waveshape and its winding characteristics are generally based on impedance characteristics of the tested winding.…”

Section: Measurement Of Impulse Winding Responses On Transformersmentioning

confidence: 99%

“…As per IEEE and IEC standards, electrical testing methods are generally followed in power industries to provide the guidelines for the detection of insulation failure virtually during impulse testing of transformer [3,4]. The main issues with various electrical testing methods are a prediction of minor failure in the transformer [5][6][7][8][9][10][11][12][13]. During visual inspections on the measured transient signal during the impulse test, if there are not any deviations in the shape of applied impulse voltage and neutral current after each voltage shot, the transformer is considered to have the capability to withstand the rated impulse voltage [1,2].…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Statistical correlation technique for transient signal analysis during impulse testing of transformers

Garg

Sharma

Jain

et al. 2020

IET sci. meas. technol.

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The reliable technique for identification of winding insulation faults in a transformer is necessary for a testing engineer during impulse test. In this study, a statistical correlation technique is proposed to estimate the ‘best correlation’ between transient signals for passed (withstood the impulse voltage) or failed (not withstood) conditions of the insulations. In this study, normalised reduced impulse voltage is considered initially as a reference signal. The next successive impulse test sequences due to rated test voltage are correlated as a test signal with a reference signal using a proposed technique. It makes a ‘good correlation value along with its directions’ between the reference signal and test signal based on measured the applied impulse voltage waveshape and its winding response. The fundamentals of the correlation coefficient, curve fitting techniques, conditional variance, normalisation and time delay index are integrated effectively to predict the characteristics (degree/magnitude and direction) of correlation between the signals. 2.5‐MVA 11/0.433 kV (distribution transformer), 0.3‐MVA 34.5/0.415 kV (earthing transformer) and 250‐MVA 500/275/33 kV (power transformer) are effectively utilised to validate proposed technique. The advantage of the proposed technique is validated with partial discharge detection in windings due to an impulse voltage application using an 11 kV single‐layer winding.

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Section: Principles Of Fault Detection During Impulse Testingmentioning

confidence: 99%

Section: Measurement Of Impulse Winding Responses On Transformersmentioning

confidence: 99%

Section: Measurement Of Impulse Winding Responses On Transformersmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Statistical correlation technique for transient signal analysis during impulse testing of transformers

Garg

Sharma

Jain

et al. 2020

IET sci. meas. technol.

View full text Add to dashboard Cite

show abstract

“…Transformer windings form a complex distributed resistive-inductive-capacitive (RLC) network, reflecting various internal resonances. Hence, the internal overvoltages recorded along the winding height may vary from the proportionally attenuated incoming external transients [3,[23][24][25][26][27]. For this reason, study on internal transient waveforms in transformers, subjected to standard and non-standard excitations, including superimposed waveforms containing oscillating components, are important for the development of more reliable transformers.…”

Section: Introductionmentioning

confidence: 99%

Propagation of Overvoltages in the Form of Impulse, Chopped and Oscillating Waveforms in Transformer Windings—Time and Frequency Domain Approach

2020

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This paper describes a comparison of overvoltage propagation in transformer windings. Expanding and evolving electrical networks comprise various classes of transient waveforms, related to network reconfigurations, failure stages and switching phenomena, including new sources based on power electronics devices. In particular, the integration of renewable energy sources—mainly solar and wind—as well as expanding charging and energy storage infrastructure for electric cars in smart cities results in network flexibility manifested by switching phenomena and transients propagation, both impulse and oscillating. Those external transients, having a magnitude below the applied protection level may have still a considerable effect on winding electrical insulation in transformers, mainly due to internal resonance phenomena, which have been the root cause of many transformer failures. Such cases might occur if the frequency content of the incoming waveform matches the resonance zones of the winding frequency characteristic. Due to this coincidence, the measurements were performed both in time and frequency domain, applying various classes of transients, representing impulse, chopped (time to chopping from 1 µs to 50 µs) and oscillating overvoltages. An additional novelty was a superposition of a full lighting impulse with an oscillating component in the form of a modulated wavelet. The comparison of propagation of those waveforms along the winding length as well as a transfer case between high and low voltage windings were analyzed. The presented mapping of overvoltage prone zones along the winding length can contribute to transformer design optimization, development of novel diagnostic methodology, improved protection concepts and the proper design of modern networks.

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Investigation of Novel Solid Dielectric Material for Transformer Windings

Ersoy,

Atalar,

Aydoğan

2023

Polymers

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Improvement techniques aimed at enhancing the dielectric strength and minimizing the dielectric loss of insulation materials have piqued the interest of many researchers. It is worth noting that the electrical breakdown traits of insulation material are determined by their electrochemical and mechanical performance. Possible good mechanical, electrical, and chemical properties of new materials are considered during the generation process. Thermoplastic polyurethane (TPU) is often used as a high-voltage insulator due to its favorable mechanical properties, high insulation resistance, lightweight qualities, recovery, large actuation strain, and cost-effectiveness. The elastomer structure of thermoplastic polyurethane (TPU) enables its application in a broad range of high-voltage (HV) insulation systems. This study aims to evaluate the feasibility of using TPU on transformer windings as a solid insulator instead of pressboards. The investigation conducted through experiments sheds light on the potential of TPU in expanding the range of insulating materials for HV transformers. Transformers play a crucial role in HV systems, hence the selection of suitable materials like cellulose and polyurethane is of utmost importance. This study involved the preparation of an experimental setup in the laboratory. Breakdown tests were conducted by generating a non-uniform electric field using a needle–plane electrode configuration in a test chamber filled with mineral oil. Various voltages ranging from 14.4 kV to 25.2 kV were applied to induce electric field stress with a step rise of 3.6 kV. The partial discharges and peak numbers were measured based on the predetermined threshold values. The study investigated and compared the behaviors of two solid insulating materials under differing non-electric field stress conditions. Harmonic component analysis was utilized to observe the differences between the two materials. Notably, at 21.6 kV and 25.2 kV, polyurethane demonstrated superior performance compared to pressboard with regards to the threshold value of leakage current.

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Investigations of transformer winding responses to standard full and chopped lightning impulses

Cited by 3 publications

References 8 publications

Statistical correlation technique for transient signal analysis during impulse testing of transformers

Statistical correlation technique for transient signal analysis during impulse testing of transformers

Propagation of Overvoltages in the Form of Impulse, Chopped and Oscillating Waveforms in Transformer Windings—Time and Frequency Domain Approach

Investigation of Novel Solid Dielectric Material for Transformer Windings

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