Behaviour of a uniaxially orientated polyethylene tape/oil insulating system under electrical and thermal stresses

Abstract

A u n i a x i a l l y o r i e n t a t e d polyethylene (UOPEJ t a p e has been used f o r t h e p r e s e n t series of experiments. A s e r i e s of experiments were conducted i n t o the e f f e c t of e l e c t r i c a l and thermal s t r e s s e s on t h e t a p e . IMTRODUCTION A u n i a x i a l l y o r i e n t a t e d polyethylene (UOPE) t a p e was developed by Brookhaven

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

“…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.…”

“…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].…”

“…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].…”

“…Elevated temperature tests turn out to give lower breakdown strength, which may be due to an increase of the thickness of the amorphous region of the polymer and to the greater solubility and diffusivity of the gaseous byproducts. Greater solubility and diffusivity in turn will sustain discharges of a certain magnitude and will possibly cause discharges of an even larger magnitude, which will erode the polymer with accelerating rate and will eventually lead to failure [33][34][35].…”

Alternative Fluids – with a Particular Emphasis on Vegetable Oils – as Replacements of Transformer Oil: A Concise Review

“…This, however, depends on the nature of the fluid. Other insulating liquids release gas bubbles, whereas others absorb gas bubbles, as was noted in [8,35]. Besides the factors, it would be fitting to add that for some of the liquids mentioned above, there are serious objections.…”