Electric stresses on transformer winding insulation under standard and non-standard impulse voltages

Bhuyan, Kaveri; Chatterjee, Saibal

doi:10.1016/j.epsr.2015.01.019

Cited by 16 publications

(10 citation statements)

References 26 publications

(30 reference statements)

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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%

“…If there is no fault (i.e. at i n ( t ) = i f ( t )) due to application of 1 FW [3, 4, 7–16 ] then difference current

normalΔ I_{n f} = (∥, (∥, i_{n} ()(, t) - i_{f} ()(, t)))

()(, here (∥, (∥, i_{n} ()(, t))) = \int_{0}^{T} i_{n} (t) normald t normaland ∥i_{f} (t)∥ = \int_{0}^{T} i_{f} (t) normald t)

and applied impulse voltage waveshape differences

normalΔ V_{n f} = (∥, (∥, v_{n} ()(, t) - v_{f} ()(, t))) = 0

()(, here (∥, (∥, v_{n} ()(, t))) = \int_{0}^{T} v_{n} (t) normald t normaland ∥v_{f} (t)∥ = \int_{0}^{T} v_{f} (t) normald t)

is zero [7–16 ]. If there is any mismatch between the responses, then impulse test is not continued and it is declared that, winding is failed to withstand the impulse voltage.…”

Section: Principles Of Fault Detection During Impulse Testingmentioning

confidence: 99%

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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%

“…If there is no fault (i.e. at i n ( t ) = i f ( t )) due to application of 1 FW [3, 4, 7–16 ] then difference current

normalΔ I_{n f} = (∥, (∥, i_{n} ()(, t) - i_{f} ()(, t)))

()(, here (∥, (∥, i_{n} ()(, t))) = \int_{0}^{T} i_{n} (t) normald t normaland ∥i_{f} (t)∥ = \int_{0}^{T} i_{f} (t) normald t)

and applied impulse voltage waveshape differences

normalΔ V_{n f} = (∥, (∥, v_{n} ()(, t) - v_{f} ()(, t))) = 0

()(, here (∥, (∥, v_{n} ()(, t))) = \int_{0}^{T} v_{n} (t) normald t normaland ∥v_{f} (t)∥ = \int_{0}^{T} v_{f} (t) normald t)

is zero [7–16 ]. If there is any mismatch between the responses, then impulse test is not continued and it is declared that, winding is failed to withstand the impulse voltage.…”

Section: Principles Of Fault Detection During Impulse Testingmentioning

confidence: 99%

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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“…Such tests of voltage exposure and overvoltage propagation allow a check of transformer immunity and are related to both distribution and power units. In the case of power transformers, standards [15][16][17][18][19] also require compliance with tests based on tail chopped lightning impulse. This kind of extended testing is recommended in configurations where the transformer is protected by a spark-gap or is operating in connection to a gas insulated substation.…”

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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“…Another important observation is that the naturally occurring transients do not always have the standard waveshape . The actual lightning or switching surges consist of a wide variety of complex waveforms differing in amplitude and waveshape . Barker et al determined the characteristics of lightning surges occurring at distribution arresters and identified damages and faults caused by lightning in distribution system arresters.…”

Section: Introductionmentioning

confidence: 99%

“…They measured 1309 lightning surge waveshapes and obtained characteristic distributions of their rates‐of‐rise, rise times, decay times and other relevant parameters. There are considerable differences in the characteristics of the standard and non‐standard impulse voltages in terms of steepness of the wave, instant of chopping, time to collapse, frequency of oscillations, overshoot near the peak and so on that are important to be taken into account while evaluating insulation coordination . The main objective of our work is to investigate the electrical stresses on surge arresters caused by standard and non‐standard lightning impulse.…”

Section: Introductionmentioning

confidence: 99%

Simulation of overvoltage stresses on surge arrester insulation

Bhuyan

Chatterjee

2015

Int. Trans. Electr. Energ. Syst.

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SUMMARYImpulse voltage testing is generally carried out for assessing the insulation strength of power equipment using standard impulse voltage waveforms in high-voltage laboratory. However, in actual field, the power equipment experiences standard and non-standard lightning impulse voltages. The main objective of this work is to analyse the voltage stress on surge arresters under standard and non-standard lightning impulse waveforms. Surge arrester models are developed in MATLAB (The MathWorks, Inc., Natick, Massachusetts, United States), and residual voltage test results are compared with manufacturer data for validation. Impulse voltage test is performed on the Institute of Electrical and Electronics Engineers surge arrester model using standard and non-standard lightning impulse voltage waveforms. The obtained test results showed that non-standard impulses have the potential to develop higher voltage stress and hence pose a high risk to surge arresters. However, results of this study provide the basis for further laboratory-based investigation considering a wide variety of impulse voltage waveforms representing the real lightning overvoltages. The test results will contribute to identify the need for modifying existing test standards or introducing new standards for impulse testing of surge arrester.

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Electric stresses on transformer winding insulation under standard and non-standard impulse voltages

Cited by 16 publications

References 26 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

Simulation of overvoltage stresses on surge arrester insulation

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