Thermal aging and degradation of thin films of natural ester dielectric liquids

Viertel, Julia; Ohlsson, Katarina; Singha, Santanu

doi:10.1109/icdl.2011.6015478

Cited by 24 publications

(12 citation statements)

References 3 publications

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“…On the other hand, it was also suggested in [2,8] that the relatively high acidities of aged natural esters do not seem to be harmful to cellulose insulation and dielectric strength of natural esters remain unchanged after thermal ageing. In addition, test results in [5] showed a certain relationship between oxidation stability of natural esters and their oleic acid (mono-saturated acid) content. Natural esters with high oleic acid content have long time oxidation stability.…”

Section: Bmentioning

confidence: 97%

“…Investigations in [2,[5][6][7] showed that viscosity, total acid number and power factor in natural esters after thermal ageing increase obviously and can be regarded as good makers to evaluate gelling/oxidation behaviour of natural esters. On the other hand, it was also suggested in [2,8] that the relatively high acidities of aged natural esters do not seem to be harmful to cellulose insulation and dielectric strength of natural esters remain unchanged after thermal ageing.…”

Section: Bmentioning

confidence: 99%

“…These films could inhibit mechanical operation and increase power factor of coil and should be avoided as far as possible [3]. In addition, it is also suspected that formation of these thin films of gelled natural ester might occur on hot surfaces in transformers if oxygen is not strictly excluded from transformers in service [5].…”

Section: A Brief Introduction To Natural Ester Transformer Liquidsmentioning

confidence: 99%

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Gelling behaviour of natural ester transformer liquid under thermal ageing

Lü

Liu

Wang

2012

2012 International Conference on High Voltage Engineering and Application

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There have been increasing interests on natural esters as potential substitutes to conventional mineral oils in transformers, due to their less-flammable, non-toxic and environmentally friendly properties. The application has been successful in traction and distribution transformers with sealed type. But the susceptibility to oxidation and hence the suspected gelling behaviour prevent the application of natural esters in freebreathing transformers. This paper presents an experimental study of gelling/oxidation behaviour of thin films of a natural ester under thermal ageing. Ageing experiments were carried out with presence of air at different temperatures of 120 ˚C and 20 ˚C and durations up to 2 years. The gelling/oxidation behaviour of natural ester was evaluated in terms of changes in viscosity and acidity. Results showed that both viscosity and acidity can be used to assess gelling/oxidation behaviour of natural ester from initial liquid phase to eventually gelled form. In addition to temperature, the thickness of the thin film samples has a significant effect on the gelling speed, i.e. the thinner of the film, the faster of the gelling speed.

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Section: Bmentioning

confidence: 97%

Section: Bmentioning

confidence: 99%

Section: A Brief Introduction To Natural Ester Transformer Liquidsmentioning

confidence: 99%

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Gelling behaviour of natural ester transformer liquid under thermal ageing

Lü

Liu

Wang

2012

2012 International Conference on High Voltage Engineering and Application

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“…1 [3,4]. The fatty acids in triglycerides can determine the physical and chemical properties of vegetable oils such as viscosity, melting/pour points, oxidation stability and ageing characteristics [5]. For example, as the percentage of unsaturated fatty acids contents increase, the melting and pour points will decrease [6].…”

Section: Introductionmentioning

confidence: 99%

Investigation on the Dielectric, Physical and Chemical Properties of Palm Oil and Coconut Oil under Open Thermal Ageing Condition

Mohamad¹,

Azis²,

Jasni³

et al. 2016

Journal of Electrical Engineering and Technology

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-In this paper, a study is carried out to investigate the dielectric, physical and chemical properties of Palm Oil (PO) and Coconut Oil (CO) under open thermal ageing condition. The type of PO used in this study is Refined Bleached and Deodorized Palm Oil (RBDPO) Olein. The ageing experiment was carried out at 85 °C and 115 °C for 1, 3, 5, 7 and 14 days. Several parameters were measured such as AC breakdown voltage, dielectric dissipation factor, relative permittivity, resistivity, viscosity, moisture and acidity throughout the ageing duration. Based on the study, it is found that there are no significant changes on the AC breakdown voltages and relative permittivities for both RBDPO and CO. At ageing temperature of 115°C, there are clear reduction trends of dielectric dissipation factor for CO and resistivities for most of RBDPO. On the other hand, no clear trends are observed for viscosities, moisture and acidities of RBDPO and CO throughout the ageing duration.

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“…Thin films of NE oil naturally occur in an untanked core and coils, hoses, fittings essentially oxidise when such surfaces contact with air [83,190]. Consequently, a stiff gummy gel is formed.…”

Section: Experimental Experience On Thin Film Oxidation Of Nementioning

confidence: 99%

Condition monitoring of biodegradable oil filled transformer

Mudiyanselage¹,

Bandara²

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Natural and synthetic ester insulating oils have higher fire points and excellent biodegradable characteristics. Therefore, in order to reduce the adverse environmental impact and to improve the fire safety of transformers, there is an increasing demand for natural and synthetic ester insulating liquids as a transformer insulating oil. However, present understanding on ageing behaviour of ester oil-paper composite insulation system and knowledge on application of existing condition monitoring tools for ester based insulation systems are inadequate. This impedes the cost effective and reliable field applications of ester insulating oils, particularly application of natural esters. To reduce this knowledge gap, series of controlled ageing experiments are performed in this research project to provide a better and comprehensive understanding on ageing behaviour of ester oil-paper insulation systems. Furthermore, applicability of existing chemical and electrical based condition monitoring techniques for ester oil-paper insulation systems is systematically investigated in this research project.In this thesis, ageing behaviour of dry pressboard insulation in mineral and three different ester insulating oils under simulated transformer operating environment is investigated. Moreover, the ageing behaviour of natural ester-pressboard composite insulation in moisture rich environment is also compared with that of mineral oil-pressboard system. Degree of polymerisation of pressboard samples measured at different ageing interval is used in this research to determine the ageing condition of pressboard. Moreover, applicability of oil related diagnostic parameters such as concentration of dissolved furanic compounds, acidity value, Dielectric Dissipation Factor (DDF), viscosity and colour to assess the degree of degradation of both ester and mineral insulating oils is thoroughly investigated in this research project. The potential of FTIR (Fourier Transform Infrared spectroscopy) techniques for characterising the degree of degradation of paper insulation is also discussed in this thesis. In addition, this thesis concentrates on characterisation of the charge dynamic in insulating oil through modelling of their dielectric responses.The comparison of gassing behaviour of ester and mineral insulating oils under two different low temperature faults and low energy electric discharge condition is also presented in this thesis.Dissolved Gas Analysis (DGA) results presented in this thesis depicts that faults gases detected in ester and mineral oil samples subjected to a similar fault are akin in type but quantitatively different. The quantity of fault gases produced in two different natural ester oils is also dissimilar.For example, soy-based natural ester produces a large quantity of ethane (C2H6) under low temperature overheating condition than sunflower oil based natural ester. Therefore, this research project investigates the applicability of well-established DGA interpretation schemes namely Duval II | P a g e triangle, IE...

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Thermal aging and degradation of thin films of natural ester dielectric liquids

Cited by 24 publications

References 3 publications

Gelling behaviour of natural ester transformer liquid under thermal ageing

Gelling behaviour of natural ester transformer liquid under thermal ageing

Investigation on the Dielectric, Physical and Chemical Properties of Palm Oil and Coconut Oil under Open Thermal Ageing Condition

Condition monitoring of biodegradable oil filled transformer

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