Time to failure of medium-voltage form-wound machine turn insulation stressed by unipolar square waves

Moonesan, Mohammad Saleh; Jayaram, S.; Cherney, E.A.

doi:10.1109/tdei.2015.005201

Cited by 16 publications

(6 citation statements)

References 14 publications

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“…Increased switching speeds and frequencies, however, raise issues concerning the long-term endurance of organic insulation materials employed in MV converter systems [4,5]. The accelerated degradation and premature failure of insulation systems exposed to inverter-type medium voltages in the presence of partial discharge (PD) is a largely investigated topic [6][7][8][9][10], and PD is recognized as one of the main risk factors associated with this type of voltage stress: a.…”

Section: Introductionmentioning

confidence: 99%

Endurance of Polymeric Insulation Foil Exposed to DC-Biased Medium-Frequency Rectangular Pulse Voltage Stress

et al. 2019

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The endurance of polymeric insulation foil is investigated under a mixed medium-voltage stress (DC + medium-frequency rectangular pulse) by means of accelerated lifetime testing. A dedicated setup is used that allows us to selectively eliminate the known risk factors for premature insulation failure under medium-frequency pulse voltage stress: partial discharges (PDs) during pulse transitions, excessive dielectric heating, and systemic overvoltages. The obtained results on polyethylenterephtalat (PET) insulation foil suggest that the adequate consideration of these factors is sufficient for eliminating the adverse effects of the pulse modulation under the investigated conditions. Indeed, if all mentioned risk factors are eliminated, the time to failure observed under a pure DC stress is shorter than with a superimposed pulse (keeping the same peak voltage). There is then no indication of an additional detrimental “per pulse” degradation process (i.e., the time to failure is not dependent on pulse frequency). In contrast, when repetitive PDs are present, the lifetime under combined DC + rectangular pulse stress strongly decreases with increasing pulse switching frequency. PD erosion of the foil is quantified by means of confocal microscopy, and the applicability of the streamer criterion for predicting PD inception is discussed.

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Section: Introductionmentioning

confidence: 99%

Endurance of Polymeric Insulation Foil Exposed to DC-Biased Medium-Frequency Rectangular Pulse Voltage Stress

et al. 2019

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“…Based on such lifetime curves, it can be decided which insulation material is most suitable for a particular application and design guidelines for minimum insulation thicknesses necessary for a desired lifetime can be extracted from the lifetime curves and can be implemented in the design. While a significant amount of work has been done on lifetime of different insulation material at 50 Hz AC, experimental data available in the literatures for insulation lifetime under pulse stress at high frequencies is limited to several kHz [4][5][6]. Different factors such as magnitude of the electric stress, frequency, temperature, rise time of the waveform, ON period of the waveform, presence of partial discharges, environment, etc.…”

Section: Introductionmentioning

confidence: 99%

“…Different values for k is proposed by different researchers, with k=1 [3] and k between 0.6-0.7 [5].…”

Section: Introductionmentioning

confidence: 99%

Lifetime of Oil-Impregnated Paper under Pulse Stress at Different Frequencies

Mathew¹,

Niasar²

2022

NORD-IS

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With the increasing penetration of power electronic interfaces in the power grid, insulation materials will begin to experience stresses at higher frequencies than the conventional 50 Hz AC. This article studies the lifetime curves of oil-impregnated paper (OIP) under pulsed stresses and compares them at 10 kHz and 50 kHz. A pulse modulator is constructed consisting of a rectified DC supply feeding an H-bridge pulse driver connected to a 4:200 pulse transformer. The modulator is used to apply medium voltage pulse waveforms with rise-times of Tr ≈ 1.8 µs across single-layer OIP samples. The results clearly show that an increase in pulse frequency significantly accelerates insulation ageing. However, it is also observed that below a certain threshold of field strength, the slope of the lifeline decreases dramatically thereby indicating decelerated ageing. Possible reasons for this phenomenon are also discussed in this article.

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“…While the breakdown and lifetime curve of different insulation material have been widely investigated for 50 Hz AC, the impact of frequency and voltage waveform on insulation degradation are not conclusive. Significant amount of work has been done on machine winding insulation [1][2][3][4][5][6].…”

Section: Introductionmentioning

confidence: 99%

“…In general, it is concluded that when partial discharge exists, the lifetime decreases with the increase of switching frequency (lifetime ∝ − ). Factor k is obtained to be 1 according to [1] and less than 1 (typically between 0.6-0.8) according to [2]. Faster rise time of the voltage pulses, in case PD is present, results in lower lifetime and higher amplitude of PD [3,4].…”

Section: Introductionmentioning

confidence: 99%

Aging of oil-impregnated paper at different frequencies

Niasar

Zhao

2021

2021 IEEE International Conference on the Properties and Applications of Dielectric Materials (ICPADM)

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In this work, breakdown strength and lifetime curve of oil-impregnated paper (OIP) are compared at 50Hz and 1500 Hz. For the ramp breakdown tests, sinusoidal voltage ramp of / is used. The ramp breakdown experiments is conducted on OIP samples made of single and double sheets of OIP. Weibull plots and interpretation of the results are presented. In order to obtain lifetime curves, a step sinusoidal voltage waveform whose peak value is close to the minimum OIP ramp breakdown voltage is applied on single sheet of OIP samples. Time to breakdown is measured, and each experiment is repeated between 20-30 times to obtain good statistical results. The experiments were focused on four different voltage levels and the lifetime curves are plotted for those two target frequencies. Parameters of the lifetime curves are extracted and the interpretation is given.

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Time to failure of medium-voltage form-wound machine turn insulation stressed by unipolar square waves

Cited by 16 publications

References 14 publications

Endurance of Polymeric Insulation Foil Exposed to DC-Biased Medium-Frequency Rectangular Pulse Voltage Stress

Endurance of Polymeric Insulation Foil Exposed to DC-Biased Medium-Frequency Rectangular Pulse Voltage Stress

Lifetime of Oil-Impregnated Paper under Pulse Stress at Different Frequencies

Aging of oil-impregnated paper at different frequencies

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