Study of samples of composite insulating system under electrical and thermal stresses

Danikas, M. G.

doi:10.1109/57.45980

Cited by 14 publications

(8 citation statements)

References 13 publications

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“…Previous work on this has shown that the AC breakdown strength of a polypropylene laminated paper/oil combination decreases as swelling worsens [37]. Similar conclusions were reached with another composite insulating system consisting of UOPE/DDB oil [33][34][35]. In [38], the problem of solid/liquid combination was attacked from another angle, namely that of the interface and also in terms of the water content.…”

Section: Impregnation Effectsupporting

confidence: 70%

“…A combination of polymer and of a low viscosity absorbing liquid was proposed several years ago. That was a combination of uniaxially orientated polyethylene (UOPE) and dodecylbenzene (DDB) oil [33][34][35]. Experimental results indicated that since collision impact of electrons accelerated in the free volume is the dominant cause for electrical tree initiation, liquid impregnation is a promising way to improve the performance of polymeric materials and to rise the breakdown strength [36].…”

Section: Impregnation Effectmentioning

confidence: 99%

“…However, as mentioned in [29], orientated polymers may be subjected to a rapid shrinkage above a critical temperature. Degradation of UOPE films has been observed several years ago, especially when these are combined with DDB oil [33][34][35]. Besides the fact that such a composite system (UOPE/DDB oil) starts having problems at about 110 o C, oils with aromatic constituents can cause crazing to polymers much more easily than polybutene oil [46,47].…”

Section: Impregnation Effectmentioning

confidence: 99%

See 2 more Smart Citations

Some Factors Affecting the Breakdown Strength of Solid Dielectrics: A Short Review

Danikas

Vardakis

Sarathi

2020

Eng. Technol. Appl. Sci. Res.

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Section: Impregnation Effectsupporting

confidence: 70%

Section: Impregnation Effectmentioning

confidence: 99%

Section: Impregnation Effectmentioning

confidence: 99%

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Some Factors Affecting the Breakdown Strength of Solid Dielectrics: A Short Review

Danikas

Vardakis

Sarathi

2020

Eng. Technol. Appl. Sci. Res.

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“…This is probably due to the existing probability of weak points of the electrical insulation at butt gaps [49]. Regarding the role of butt gaps and their related parameters, there is a striking similarity between the observations of the above publication and those reported using conventional insulating systems [50,51], i.e. that the butt gaps -if not well impregnated -may be the weak point of a composite insulation.…”

Section: Systemssupporting

confidence: 57%

Insulating Materials at Very Low Temperatures: A Short Review

Malelis

Danikas

2020

Eng. Technol. Appl. Sci. Res.

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In this paper, a short review is given on insulating materials at very low temperatures. Various insulating materials are investigated in terms of phenomena such as partial discharges. Some of the factors affecting the behavior of the insulating materials at very low temperatures, such as the quality of electrode surface, the stressed insulation volume and the existing bubbles, are also reported and commented upon. Proposals for future research are also discussed.

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“…However, a larger void is more dangerous than a smaller one, since the larger void not only discharges at a lower stress level, but also dissipates more energy in each discharge [34], and thus causes more severe insulation damage [34,35]. Therefore, to specify the maximum allowable void is the current practice in cable manufacturing [28,29].…”

Section: Recent Research However By Bruning and Coworkers [2mentioning

confidence: 99%

Insulation thickness determination of polymeric power cables [and reply]

Danikas¹,

Cheng²

1995

IEEE Trans. Dielect. Electr. Insul.

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highly interesting recent paper [l] brought to the A reader's attention the relation which exists between insulation thickness and cavity size in polymeric cables. The author of [l] reaches the conclusion that decreasing the maximum cavity size in a given cable allows an increase in the cable working voltage. A number of assumptions in the aforementioned paper, however, need some more explanation.(1) In the paper, the opinion that ". . . the discharge inception stress represents the critical value for infinitely long life" seems to be adopted. Inception stress depends on the sensitivity of the discharge detection equipment.Recent research, however, by Bruning and coworkers [2, 31 has shown that it is possible to get insulation deterioration even below the so-called inception level. Whether such deterioration is due to minute discharges not detected by conventional methods [4] or to some chemical processes [2,3] is of course still open to question. Voltage values below the inception level do not necessarily guarantee long insulation life. We would appreciate the author's comments on that.(2) In the paper it is also noted that "during an increase in loading and cable temperature, the pressure in the void rises and gas gradually diffuses through the insulation. When load is decreasing and the cable temperature is dropping, the pressure in the void will decrease below atmospheric pressure". Having said that, how the author of [l] relates the behavior of discharges in cavities, and we mean by that the discharge inception/extinction behavior, to the loading conditions? Theories about the extinction of discharges in cavities abound, and there are researchers claiming that an increase in cavity pressure may lead to discharge extinction [5-71, whereas others claim that the continuous consumption of oxygen leads to pressure reduction in the cavity and consequently to discharge extinction [8,9]. Although this subject is not treated extensively in [l], we would welcome the author's comments on that.(3) In another paragraph of his paper, the author claims that ''. . . discharges at small intensity (-2 pC), which will occur when the system is operated at a voltage higher than its rating, are innocuous". My personal experience with polyethylene [lo, 111 is that even small discharges (-1 to 2 pC) at relatively low electric stresses may lead to a transformation of the insulation surface. Such transformations were observed by Mayoux and coworkers [E], who also noted that there is a distinction between transformation and deterioration. Since we think that the aforementioned claim is not undisputed, we would appreciate the author's clarifications of this point.(4) In the Results and Discussion section the author points out that ". . . intervoid influences are so small as to be negligible. Therefore . . . all voids can be ignored except the one for which the discharge inception voltage is the minimum". What is the evidence for that? Recent theoretical investigation [13] has shown that closely coupled cavities in solid dielectrics may...

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Study of samples of composite insulating system under electrical and thermal stresses

Cited by 14 publications

References 13 publications

Some Factors Affecting the Breakdown Strength of Solid Dielectrics: A Short Review

Some Factors Affecting the Breakdown Strength of Solid Dielectrics: A Short Review

Insulating Materials at Very Low Temperatures: A Short Review

Insulation thickness determination of polymeric power cables [and reply]

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