Response of EHV Grid Transformers to System-Originated Oscillatory Switching Transients

Mitra, Poulomi; De, Abhinandan; Chakrabarti, A.

doi:10.1109/tpwrd.2011.2176149

Cited by 9 publications

(13 citation statements)

References 6 publications

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“…Even if the transformer damage happened, their discrimination is still important to diagnose the event and add a suitable mitigation method. As the internal transformer resonance phenomenon is characterized by high-frequency overvoltages during the transient period [7], the core flux decreases where the voltage is proportional to the frequency and flux (E  f.). However, the ferroresonance is characterized by the saturated iron core [9], high magnetizing currents, sustained overvoltages, and distortion in the waveforms.…”

Section: Investigation and Distinguishing Algorithmsmentioning

confidence: 99%

“…When the transient surge waveform contains frequency matched the resonance frequency of the transformer windings, the internal transformer resonance is happened and provides transient overvoltages. However, it can result in insulation breakdown for transformer winding due to the resulted highfrequency overvoltages at the secondary side [3][4][5][6][7][8]. Overvoltage protections such as surge arrestor can be installed at the secondary side of the transformer in order to mitigate such induced overvoltages .…”

Section: Introductionmentioning

confidence: 99%

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Investigation of Resonance and Ferroresonance Overvoltages due to Cable-Transformer Interactions

Nassar

Taalab

Izzularab

et al. 2020

ERJ. Engineering Research Journal

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In this paper, the resonance and ferroresonance phenomena are deeply investigated considering two different cable-transformer power systems. The internal transformer resonance overvoltage case is initiated due to a single-phase earth fault, while the studied ferroresonance case is due to a single-phase switching in the source feeding an unloaded transformer via a power cable. The resulted secondary overvoltage and the core flux signatures are used as a classifier, where the transient features are extracted using three algorithms. Although the voltage frequency spectrum and phase-plane diagrams have been previously utilized for the ferroresonance mode evaluation, they are exploited in this paper for the comparison study and accordingly for the detection of resonance and ferroresonance phenomena. Salient features found in the transients extracted using the well-known DWT are used as inputs of the third algorithm. A new detection approach is attained based on the DWT-based transient feature extraction of resonance and ferroresonance overvoltages.

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Section: Investigation and Distinguishing Algorithmsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Investigation of Resonance and Ferroresonance Overvoltages due to Cable-Transformer Interactions

Nassar

Taalab

Izzularab

et al. 2020

ERJ. Engineering Research Journal

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show abstract

“…Failure data analysis of EHV transformers [10][11][12][13][14] reveal (based on internal inspection and post-mortem), that most of them are traceable to insulation-breakdowns because of overvoltages arising from resonances occurring at highly stressed regions of the winding. Such instances of failure (resulting from insulation-overstress) is rather intriguing, because, meticulous care had been initially exercised during various stages of its design, manufacture and testing.…”

Section: Background and Motivationmentioning

confidence: 99%

“…The logic is fairly simple; a winding with fewer resonant frequencies is less-likely to experience resonant overvoltages. Notwithstanding these features, in-service failures of EHV transformers with interleaved windings have been reported and this is a matter of serious concern to designers and engineers, particularly so, considering the reasons put forward to explain failures [10,11].…”

Section: Introductionmentioning

confidence: 99%

Interleaved winding and suppression of natural frequencies

Pramanik

Anees

Satish

2013

IET Electric Power Applications

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Ideally, it is desirable to design and manufacture a transformer winding that can render all its internal resonances nonexcitable. This study examines the effectiveness of an interleaved winding in achieving this goal. While investigating its effectiveness, it led to the establishment of a much desired theoretical basis that reinforces the reasons put forward in the literature to explain internal insulation failures observed in interleaved windings used in extra high voltage (EHV) transformers. Numerical calculations along with experimental verification on actual transformer windings are presented. This study reveals that most of the natural frequencies that are normally non-excitable in the line and neutral current responses of an interleaved winding have been rendered excitable in the disk-to-disk voltages, thus, providing favourable conditions for insulation overstress because of resonant overvoltages. Prevalence of such a condition is an inherent characteristic of interleaved windings.

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“…While, the transformer test standards [4–6] traditionally emphasised on evaluating the strength and quality of transformer insulation under standard lightning and switching impulses, response of transformers under oscillatory transient voltages was not given due attention. However, research in [7, 8] demonstrated the adverse impact of low‐amplitude oscillatory switching transients on grid‐connected transformer windings and established that internal resonance in transformers can be potentially hazardous, as the free oscillations can produce voltage rise at various internal nodes of the winding which can even exceed the incident voltage.…”

Section: Introductionmentioning

confidence: 99%

Development of a new multi‐graded winding to alleviate resonant characteristic of EHV transformers

De¹,

Bandyopadhyay

2020

IET Generation, Transmission & Distribution

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Response of EHV Grid Transformers to System-Originated Oscillatory Switching Transients

Cited by 9 publications

References 6 publications

Investigation of Resonance and Ferroresonance Overvoltages due to Cable-Transformer Interactions

Investigation of Resonance and Ferroresonance Overvoltages due to Cable-Transformer Interactions

Interleaved winding and suppression of natural frequencies

Development of a new multi‐graded winding to alleviate resonant characteristic of EHV transformers

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