Electrical Insulation Deterioration Treated as a Chemical Rate Phenomenon

Dakin, T. W.

doi:10.1109/t-aiee.1948.5059649

Cited by 415 publications

(157 citation statements)

References 7 publications

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“…This model was first introduced in [7] and it relates the thermal ageing to the rate of a temperature dependent chemical reaction, through the use of the Arrhenious equation. Thermo-mechanical ageing is mainly due to mechanical shear stress between the conductor surface and the insulation.…”

Section: The Multi-stress Ageing Modelmentioning

confidence: 99%

Lifetime Consumption and Degradation Analysis of the Winding Insulation of Electrical Machines

Sciascera

Galea

Giangrande

et al. 2016

8th IET International Conference on Power Electronics, Machines and Drives (PEMD 2016)

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In this paper, a novel multi-stress model which estimates the lifetime of the winding insulation relative to its duty cycle is proposed and investigated. With an adequate implementation of this model, then an electrical machine can be designed not only in terms of its performance requirements, but also considering the associated reliability and lifetime aspects. Since thermal and thermo-mechanical stresses are considered as the main ageing factors, the model is particularly suited for low voltage, low duty cycle machines. The determination of the model parameters is based on the results of accelerated thermo-mechanical ageing tests, whose procedure is thoroughly reported in the paper. The results of the accelerated ageing tests show that the effect of thermomechanical ageing is significant even for small size, random wound windings under fast temperature rise.

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Section: The Multi-stress Ageing Modelmentioning

confidence: 99%

Lifetime Consumption and Degradation Analysis of the Winding Insulation of Electrical Machines

Sciascera

Galea

Giangrande

et al. 2016

8th IET International Conference on Power Electronics, Machines and Drives (PEMD 2016)

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“…Ageing in insulation of wound components is usually defined as the reduction in the function of the insulating materials [18]. The insulation lifetime is defined when the insulation properties of wound components deteriorate to values such that the wound components cannot operate satisfactory.…”

Section: Thermal Ageing Modelmentioning

confidence: 99%

“…Physical chemists looked at the rate of change of the concentration of certain constituents in chemical combinations in organic materials as a function of time and temperature [18]. This approach can be employed to organic electrical insulation deterioration if we know or assume that the physical properties of the insulation material is proportional to the concentration of an important constituent [18].where: P is the magnitude of the physical property in which we are interested in and C is the concentration of an important chemical constituent of the insulation materials which is being changed by the thermal stresses.The instantaneous rate of change of the number of molecules undergoing transformation with time is proportional to the number of the molecules. This relates to the chemical reactions of oxidising decomposition, polymerization, bridging and evaporation of plasticiser [18]: where: k is the reaction rate constant n is the order or rank of the reaction and t is the time.…”

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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“…Consequently, for a particular insulation material there will be a temperature beyond which it would not be safely operated. UL and IEC treat this by establishing temperature classes and assigning each insulation material to a particular temperature class, but there are three problems with the way that this is executed: (1) The class rating methodology is based on a 1948 paper [17] and has not been reexamined for more than half a century. (2) The UL methodology [18] allows classification by experience of "field performance" without any laboratory testing.…”

Section: Temperature Class Of Insulation and Deterioration Due To Agingmentioning

confidence: 99%

Research on Electrical Fires: The State of the Art

Babrauskas¹

2008

Fire Saf. Sci.

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Electrical fires-fires directly caused by the flow of electric current or by static electricity-are one of the important types of structure fires. The subsequent development of an electrical fire is generally no different than that of any other type of structural fire. But the mechanisms leading to ignition of an electrical fire are, in many cases, uniquely specialized and in need of specific research to delineate their characteristics. Despite the importance of electrical fires, there has not been any institution in the English-speaking world with a long-term commitment to research in this area. Worldwide, the situation has been much better, due to extensive research in Japan. But most of this body of work was only published in the Japanese language and, consequently, had been unavailable to most scientists and engineers in English-language countries. The publication of the Ignition Handbook presented for the first time in English many of the salient Japanese research results in this field and these, taken together with the scattered studies that have been reported in English, allow a basic understanding of physical mechanisms to be reached. The present review presents the highlights of these findings. The review of the state of the art also shows that there are still a number of gaps where even first-cut research is not available. It is urged that a systematic research effort on electrical fires be established in the US and certain high-priority topics are outlined.

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Electrical Insulation Deterioration Treated as a Chemical Rate Phenomenon

Cited by 415 publications

References 7 publications

Lifetime Consumption and Degradation Analysis of the Winding Insulation of Electrical Machines

Lifetime Consumption and Degradation Analysis of the Winding Insulation of Electrical Machines

Real-time insulation lifetime monitoring for motor windings

Research on Electrical Fires: The State of the Art

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