Electro-insulating Paper Degradation in Various Electro-insulating Fluids

Abstract

The durability and safe operation of electrical equipment and devices with mixed insulation systems (solid/fluid - electro-insulating paper/oil) is determined by the insulation aging under simultaneous and synergic actions of electrical, thermal and chemical stress factors etc. In this context, degradations of insulating paper exposed to thermal aging in 5 different types of electro-insulating fluid have been studied experimentally. Liquid chromatography determinations have shown that the total content in furan products (resulting from cellulose degradation) in mineral oils is substantially higher than in electro-insulating fluid sorts based on of synthetic ester and/or natural ester (vegetable oil). This is due to the temperature between 90 oC and 130 oC when the activation energy of the furans formation process is up to 7.5 times lower in mineral oils than in ester-based oils. Degree determinations of cellulose polymerization (viscosimetric method) before and after exposure to heat treatment indicated that mineral oils degrade the electro-insulating paper much more strongly than ester-based oils (both synthetic and natural). Obtained results by liquid chromatography and by viscosity are in accordance with the images obtained by optical microscopy (at X 100).

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].…”

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

“…In this context, many recent studies address the issue of replacing mineral oils with vegetable oils (triglycerides -natural esters), respectively comparing their behavior under the operating conditions from power transformers [32][33][34][35][36][37][38][39][40][41].…”

Ageing of Some Painting Materials Subjected to Thermal Treatment in Natural Esters

“…These experimental findings [48] may be favorable to the complex materials system (electro insulating oil / painting materials / electro insulating paper / copper) which are in direct contact inside of the transformer's tank -of course, assuming that the integrity and the adhesion of the painting system is not affected.…”

“…It should be underlined that, further to the thermooxidative ageing of the oil transformers [40][41][42][43][44][45][46] and the degradation of the electro insulating paper, highly determined by the dissolved oxygen and the humidity of the oil transformer, several toxic furfural products [47][48][49][50] and / or of flammable gases are produced [51][52][53][54][55][56][57][58] which may lead to the explosion of the oil transformer followed by devastating wildfires [55,57].…”

“…During the thermo-oxidation processes, the polymeric painting materials used for the internal painting of the transformers' tanks consume the oxygen dissolved in the transformer oil. In this way, the amount of the oxygen available for the thermo-oxidation processes of the insulating fluid and of the insulating paper is reduced, which leads to an increased stability of these materials respectively to a diminished formation of furfurals and gases [48,57].…”