Thermally Accelerated Aging of Insulation Paper for Transformers with Different Insulating Liquids

Münster, T.; Werle, Peter; Hämel, Kai; Preusel, J.

doi:10.3390/en14113036

Cited by 25 publications

(20 citation statements)

References 59 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Compared with mineral oil, natural ester could delay the pressboard ageing significantly. Compared with the result of reference [49], the k 1 value of pressboard in mineral oil and natural ester is basically consistent with the result of this experiment, which proves that our experimental results are reliable.…”

Section: Effect Of Natural Ester On Delaying the Ageing Of Pressboardsupporting

confidence: 89%

Experimental and molecular level analysis of natural ester delaying degradation of cellulose insulation polymer

Hao

Gao

et al. 2021

High Voltage

View full text Add to dashboard Cite

Developing green insulation materials has become an important direction for future research. As a new environmental insulation liquid, natural ester can effectively delay cellulose insulation polymer ageing. Mastering the mechanism of natural ester delaying the cellulose ageing could promote its application in power transformers. In this study, based on the accelerated thermal ageing of pressboard immersed in natural ester and 25# mineral oil at 120°C for 221 days, the thermal ageing rate and the levelling off degree of polymerisation (LODP) for two kinds of oil-impregnated pressboards were compared. The molecular level mechanism of natural ester delaying cellulose degradation and keeping higher LODP value was proposed using molecular dynamics simulation. At the early stage of thermal ageing, cellulose with a higher degree of polymerisation (DP) can form many hydrogen bonds with hydronium ions, and their binding energy is stronger, which can accelerate the acid hydrolysis of cellulose, causing the DP of pressboard immersed in natural ester and mineral oil to decrease rapidly. With the breaking of the cellulose molecular chain, the number of hydrogen bonds and binding energy between cellulose and hydronium ions becomes smaller and the thermal ageing rate decreases gradually. At the end stage of ageing, it is difficult for the hydronium ions to enter the crystalline cellulose, acid hydrolysis of crystalline cellulose is hard to conduct, leading to the occurrence of the LODP phenomenon. The degradation rate of cellulose in natural ester is only 50% of that in mineral oil. The cellulose LODP value in natural ester is over 200 larger than that in mineral oil. Compared with the mineral oil-cellulose system, natural ester can form hydrogen bonds with hydronium ions and lead to fewer hydronium ions in cellulose, fewer hydrogen bonds and smaller binding energy between cellulose and hydronium ions, which can reduce the acid hydrolysis reaction of cellulose. This study provides a theoretical explanation for natural esters to delay the ageing of insulation paper.

show abstract

Section: Effect Of Natural Ester On Delaying the Ageing Of Pressboardsupporting

confidence: 89%

Experimental and molecular level analysis of natural ester delaying degradation of cellulose insulation polymer

Hao

Gao

et al. 2021

High Voltage

View full text Add to dashboard Cite

show abstract

“…Finally, esters can adsorb more significant amounts of water than MO, allowing the transformer dielectric paper to operate more dryly [1]. It has been proven that this has a positive impact on the transformer loss-of-life curve and, in consequence, on the maximum permissible hottest spot temperature [6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

“…The use of ester fluids as a transformer's liquid insulation makes it necessary that both the manufacturers and the transformer's owners redefine the transformer's life management strategy [9][10][11][12]. This includes introducing changes in the design of the equipment and establishing different guidelines for the operation and the maintenance of these actives.…”

Section: Introductionmentioning

confidence: 99%

Use Performance and Management of Biodegradable Fluids as Transformer Insulation

et al. 2021

View full text Add to dashboard Cite

In recent years, the use of biodegradable fluids as liquid insulation for distribution and power transformers is spreading. The main biodegradable fluids used are natural and synthetic esters, although biodegradable hydrocarbons have been recently proposed. Biodegradable fluids have a much lower environmental impact than mineral oil, limiting the risk of soil contamination in leaks, which makes them a suitable solution for applications such as offshore transformers or railway transformers. Additionally, these fluids have a higher flash point than conventional mineral oils, which dramatically reduces the risk of fire and collateral damage derived from explosion and fire. Despite these advantageous factors, there are still some aspects that hinder the broadening of their use, such as the difference in thermal properties or the lack of accepted maintenance procedures for transformers that use them as liquid insulation. This paper presents the current status of biodegradable insulating fluids, analyzing some of their properties and discussing the aspects that are still to be investigated in order to make them a real alternative to petroleum-based fluids.

show abstract

“…The state of oil-immersed power transformer insulation is determined by the following methods: by means of analyzing cellulose degree of polymerization [3]; by indirect methods, for example, by the presence of certain gases in transformer oil [5,6]; by online monitoring of operating conditions [7,8]; based on the statistics of transformer accidents [9]; by modeling the reactions of the transformer to the predicted changes in operating factors [10].…”

mentioning

confidence: 99%

“…The values of W(n) and θ h (n) from expressions ( 9) and ( 10) are substituted into the expressions for determining the rates of relative insulation aging. As a result of the action of temperature [6,7]:…”

mentioning

confidence: 99%

Method for assessing unevenness of cellulose insulation layers aging of power transformers winding

Poliakov

Vasylevskyi

2022

Electrical Engineering & Electromechanics

View full text Add to dashboard Cite

Introduction. Improving the methods of estimating the insulation aging of the oil-immersed power transformer windings is an urgent task for transformer condition monitoring systems. The scientific novelty of the work is to take into account the uneven distribution of temperature and humidity along the vertical axis of the winding in modeling the aging of insulation and to develop methods for determining the conditions under which the aging rate of insulation in the intermediate layer will exceed aging rate in the hottest layer. The purpose of the work is to evaluate the wear unevenness of cellulose insulation based on modeling the distribution of temperature and humidity along the vertical axis of the power transformer winding. Methods. The transformer winding is mentally divided into horizontal layers of equal height, the reduction of service life is calculated in parallel for all horizontal layers. Layer with the maximum degree of aging for the entire period of operation and storage of the transformer is recognized as determining the reduction in the service life of the insulation of the transformer as a whole. A model of the interaction of winding layers is developed, with determination of temperatures, humidity, relative rate of aging of each layer due to temperature and humidity as a function of traditional design parameters such as load, cooling temperature, heat capacity and thermal resistance of transformer. The index of exceeding the aging rate by the layered method in comparison with this rate for the hottest layer is offered. The method of genetic algorithms determines the conditions for obtaining the maximum value of this index. Results. A computer model has been developed to predict the aging of the cellulose insulation of transformer windings. According to the proposed method, a layer with significantly shorter insulation aging time (in the example, time reduced by 39.18 %) than for the upper layer was determined, which confirms the feasibility of layer-by-layer monitoring and modeling of insulation aging processes of power oil-immersed transformer windings.

show abstract

Thermally Accelerated Aging of Insulation Paper for Transformers with Different Insulating Liquids

Cited by 25 publications

References 59 publications

Experimental and molecular level analysis of natural ester delaying degradation of cellulose insulation polymer

Experimental and molecular level analysis of natural ester delaying degradation of cellulose insulation polymer

Use Performance and Management of Biodegradable Fluids as Transformer Insulation

Method for assessing unevenness of cellulose insulation layers aging of power transformers winding

Contact Info

Product

Resources

About