Comparative Studies on the Behaviour of Copper in Various Electrically Insulating Fluids

Abstract

This paper presents an exhaustive study regarding the behaviour of copper in various insulating fluids when exposed to 1100C for 1000 hours in closed systems, with no access to atmospheric oxygen. Following the analysis carried out, it was found that the variation of oxygen concentration in the investigated oil samples, during the thermal treatment, may be best described using an exponential decrease versus time. Moreover, from the gas chromatography determinations with respect to the evolution of the CO and CO2 content in the oils during the thermal treatment one found out that these fit very well the Richards model, which corroborated with all the other analysis confirms the fact that the copper films undergo consistent morphological changes only when exposed to mineral oils, so that it is of paramount importance that, taking into account this aggressive character, the equipment placed in direct contact with these oils should be carefully inspected on a periodical basis. This behaviour is thought to be a direct consequence of the sulphur compounds contents for these oils, the secondary oxidation products of these compounds increasing their corrosive aggressiveness.

Thermooxidative Behavior of Some Paint Materials in Natural Ester Based Electro-insulating Fluid

“…In the case of PM-1 and PM-2 samples, carbonyl indices decrease slightly when the paper and the Cu foil are introduced in the medium, compared to samples exposed only in natural ester oil. This is due to the fact that oxygen dissolved in oil also reacts with copper foil (oxidation catalyst [68]) forming Cu 2 O and CuO [14].…”

“…Traditionally, mineral oils [1] are used as the electroinsulating fluid in the transformers, a strong biodegradable petroleum derivative [2], which, although having acceptable physical and dielectric characteristics and a relatively low cost, has a number of disadvantages such as: limited thermal stability [3][4][5][6][7][8], corrosive aggressivity due to sulfur content [8][9][10][11][12][13][14][15][16][17], reduced compatibility with the cellulose from Kraft paper -furanic products formation [18][19][20][21][22], relatively low flammability (below 150 o C) and excessive flammable gases formation [30] (high risk of explosions and devastating fires), etc. To increase thermal stability and to reduce the corrosive aggressiveness of electro-insulating oils, manufacturers often use antioxidant additives and / or corrosion inhibitors [15][16][17]31].…”

Studies on the Behavior Some Paints in Electro-insulating Fluid Based on Vegetable Esters

“…Under the practical conditions of operation, under the synergic action of thermal and electric stress, complex interactions between the components of the system leads to a series of processes such as: degradation of electroinsulating paper [1][2][3][4][5][6][7][8][9][10][11], corrosion of metal components, especially copper, with the formation of the products of corrosion that substantially reduces the insulation resistance and dielectric rigidity of the electro-insulating fluid [12][13][14][15][16][17][18][19], the formation of furans products (toxic products determined and monitored by various techniques) [3,8,[20][21][22][23], formation of the inert gases such as CO 2 as well as flammable as H 2 , CH 4 , C 2 H 4 , C 2 H 6 etc. [24][25][26][27][28][29][30][31][32][33][34].…”

“…Several studies [2,4,13,15,17,19,30,33] have highlighted that the copper components of the transformer after thermal oxidation form Cu 2 O films with catalytic effect [35,36] on the processes formation the gases by decomposing the electro-insulating fluid.…”

“…These risks can be substantially reduced by providing adequate information and education [51][52][53] to high-risk equipment managers in exploitation and mobilizing them to implement the latest technical solutions developed in the field [8,19,39].…”