Models for insulation aging under electrical and thermal multistress

Cygan, P.J.; Laghari, J.R.

doi:10.1109/14.59867

Cited by 147 publications

(45 citation statements)

References 21 publications

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“…According to previous studies (Zaretsky et al, 1989;Cygan and Laghari, 1990;Liu and Wang, 2011;Liu and Wang, 2013), a power law model was found to be suitable to represent the relationship between various parameters in dielectric insulation transformer fluids especially for lightning impulse voltages Liu and Wang, 2013). The relationship between the lightning breakdown voltage and the gap distance using power law model is based on Eq.…”

Section: Statistical Analysis Of the Lightning Breakdown Voltagesmentioning

confidence: 99%

The effect of polarity on the lightning breakdown voltages of palm oil and coconut oil under a non-uniform field for transformers application

Thien

Azis

Jasni

et al. 2016

Industrial Crops and Products

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a b s t r a c tThis paper presents a study of the lightning breakdown voltages of Palm Oil (PO) and Coconut Oil (CO) under a non-uniform field with consideration on the polarity effect at various gap distances. All tests were carried based on a needle-sphere electrode configuration and various gap distances ranging from 2 to 25 mm under positive and negative voltage polarities. Three different testing techniques were used in this study including rising-voltage, up-and-down and multiple-voltage methods. The PO used in this study was Refined, Bleached and Deodorised Palm Oil (RBDPO) Olein. Three different samples of RBDPO and one sample of CO were tested. The Weibull distribution was used as a statistical approach to determine the withstand voltages of all samples at 1% and 50% probabilities for each type of oil. Under positive voltage polarity, it was found that the 50% breakdown voltages of RBDPO and CO were comparable with Mineral Oil (MO) whereby the highest percentage of difference among all gap distances was less than 15%. RBDPO and CO have lower 50% breakdown voltages than MO under a negative lightning impulse for which the highest percentage of difference can be up to 40%.

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Section: Statistical Analysis Of the Lightning Breakdown Voltagesmentioning

confidence: 99%

The effect of polarity on the lightning breakdown voltages of palm oil and coconut oil under a non-uniform field for transformers application

Thien

Azis

Jasni

et al. 2016

Industrial Crops and Products

View full text Add to dashboard Cite

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“…Liquid chromatographic studies [3] indicated that there is no difference between various types of oil with respect to the poly aromatic contents. Oxidative and aging behavior of transformer oil.…”

Section: Structural Analysis Of Oilmentioning

confidence: 99%

Critical Investigation of Heat Transfer in Oil Cooled Transformer

2017

IJSR

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Power transformer represents the largest portion of capital investment in transmission and distribution substations.Transformer functional life is influenced by thermal, mechanical and dielectricstresses. The concept of insulation 'Thermal life 'is a useful one, in which it can set a standard level of physical condition below which insulation integrity may be prejudiced by mechanical or dielectric stresses, normally experienced in service. In power transformer, the oil serves a dual purpose as insulating and cooling medium. The heat generated in the transformer is removed by its oil surrounding the source and is transmitted either to atmospheric air or water. Thermal modeling of power transformer top-oil considering viscosity and conductivity and other relevant parameters have been taken into account in the present work and accordingly an important correlation has been derived for ONAF (oil natural air forced) type of cooling. Result shows that the transformer top oil temperature varies remarkably with respect to time.However,within the range of the data covered the plotted figures show that rapid increase in the temperature of the transformer top oil could be achieved with increasing values of time after a certain period of time.

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Section: Thermal Ageing Modelmentioning

confidence: 99%

“…The Arrhenius reaction relationship describes the dependence of chemical reaction rates on the temperature, and can be used as a basis of thermal ageing model [19]. The Arrhenius reaction relationship can be expressed as follows [19]:where: A is the frequency constant, E is the activation energy, R is the gas constant and T is the absolute temperature. t , is proportional to the reciprocal of the absolute temperature T and represents the classical expression used to plot the insulation lifetime in hours as a function of the absolute temperature T. Equation (7) can be rearranged to provide a real-time lifetime model under varying temperature conditions as follows: Fig.4.…”

mentioning

confidence: 99%

Real-time insulation lifetime monitoring for motor windings

Tshiloz

Smith

Mohammed

et al. 2016

2016 XXII International Conference on Electrical Machines (ICEM)

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I. INTRODUCTIONLECTRICAL machines are essentially wound components for modern industrial systems. During operation, the insulation materials in electrical machines are exposed to thermal stresses. These thermal stresses initiate progressive degradation of the insulation materials, which lead to the deterioration of the insulation characteristics and consequently to insulation breakdown [1]. Therefore, knowledge relating to the condition of the insulation systems and an estimation of the remaining life has become an important concern to manufacturers and users of electrical systems [2]. Real-Time lifetime prediction of insulation materials is of interest in this work. Severe winding insulation breakdown due to thermal stresses have been reported as contributing to as much as 30-40% of all stator winding failures in conventional induction machines [3]. It was also reported in [4][5][6] that thermal ageing is the dominant ageing factor and can contribute up to ≈31% of the deterioration of the insulation materials.The lifespan of the insulation is usually predicted using accelerated ageing tests. An accelerated ageing test is used in the effort to obtain failure statistics in shorter timescales. In [2,7], the lifetime of the insulation material was estimated using an electro-thermal ageing model that takes into account the combined electrical and thermal stresses in the lifetime prediction. Real-time insulation lifetime predictions during steady-state and transient operating conditions of wound components have received less attention in the available literature.The thermal ageing model based on the classical Arrhenius relationship can be adapted for real-time steadystate and transient thermal ageing predictions of the insulation materials for wound components. The key input to the insulation lifetime model is the measured temperature distribution around the winding insulation.Winding temperatures are conventionally sensed using thermocouples or resistance temperature detectors embedded on the exposed external surfaces of the electrical machine and/or windings [8]. These techniques commonly provide single-point temperature measurements that are often unreliable [8]. Moreover, these sensors come with significant challenges imposed by the location of the sensors close to or within the stator windings for example due to use of electrically conductive materials in the sensor packages as well as susceptibility to electromagnetic interference [8]. The key objective in this work is to access the capability of predicting real-time remaining life of wound components insulation materials using Fibre Bragg Grating (FBG) sensors embedded directly into the stator coils during fabrication. The FBG sensors are fibre-optic sensors that have been used in other applications, ranging from frame vibration sensing of the stator core and coil surface thermal monitoring [9][10][11][12]. The FBG sensors are small and can be laid into the middle of the coils during the wind process and can provide real-time temperature information at several...

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Models for insulation aging under electrical and thermal multistress

Cited by 147 publications

References 21 publications

The effect of polarity on the lightning breakdown voltages of palm oil and coconut oil under a non-uniform field for transformers application

The effect of polarity on the lightning breakdown voltages of palm oil and coconut oil under a non-uniform field for transformers application

Critical Investigation of Heat Transfer in Oil Cooled Transformer

Real-time insulation lifetime monitoring for motor windings

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