Comparison of Dissolved Gases in Mineral and Vegetable Insulating Oils under Typical Electrical and Thermal Faults

Abstract

Dissolved gas analysis (DGA) is attracting greater and greater interest from researchers as a fault diagnostic tool for power transformers filled with vegetable insulating oils. This paper presents experimental results of dissolved gases in insulating oils under typical electrical and thermal faults in transformers. The tests covered three types of insulating oils, including two types of vegetable oil, which are camellia insulating oil, Envirotemp FR3, and a type of mineral insulating oil, to simulate thermal faults in oils from 90˝C to 800˝C and electrical faults including breakdown and partial discharges in oils. The experimental results reveal that the content and proportion of dissolved gases in different types of insulating oils under the same fault condition are different, especially under thermal faults due to the obvious differences of their chemical compositions. Four different classic diagnosis methods were applied: ratio method, graphic method, and Duval's triangle and Duval's pentagon method. These confirmed that the diagnosis methods developed for mineral oil were not fully appropriate for diagnosis of electrical and thermal faults in vegetable insulating oils and needs some modification. Therefore, some modification aiming at different types of vegetable oils based on Duval Triangle 3 were proposed in this paper and obtained a good diagnostic result. Furthermore, gas formation mechanisms of different types of vegetable insulating oils under thermal stress are interpreted by means of unimolecular pyrolysis simulation and reaction enthalpies calculation.

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

“…Under the action of thermal stress in the ternary complex oil/paint/cellulose/Cu system, in addition to the oxygen-consuming thermo-oxidation processes, occur a series of complex gases-forming processes such as CO 2 and CO (oxidation of organic components H 2 , CH 4 , C 2 H 4 , C 2 H 6 etc. [24][25][26][27][28][29][30][31][32][33][34]. The results obtained by gaschromatography on the investigated oils, respectively the evolution during the thermal treatment at 130 o C of total content in în CO 2 , CO, H 2 , CH 4 , C 2 H 4 and C 2 H 6 -are presented synthetically in figure 8.…”

“…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].…”

Power Transformer Diagnostics, Monitoring and Design Features

“…Xiang et al [4] also presented a comparison study of the formation of dissolved gases in mineraland vegetable-insulating oils. The authors used four interpretation dissolved gas analysis (DGA) methods and they confirmed that the diagnosis methods developed for mineral oil were not suitable for the diagnosis of electrical and thermal faults in vegetable-insulating oils and needed some modification.…”

Nonlinear Autoregressive Neural Network Models for Prediction of Transformer Oil-Dissolved Gas Concentrations

“…Due to its complexity and importance, the problems of aging degree of paper insulation has been object of study in many recent works [2][3][4]. Several other tests of insulation items have been an important part of transformers fault diagnosis systems, with emphasis on chromatographic oil-dissolved gas analysis, namely dissolved gas analysis (DGA) [4][5][6][7][8][9].…”