Bubbling Phenomena in Liquid-Filled Transformers: Background and Assessment

Ghada Gmati, Ungarala Mohan Rao, Issouf Fofana (), Patrick Picher, Oscar Arroyo-Fernàndez and Djamal Rebaine
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Ghada Gmati: Department of Applied Sciences, University of Quebec in Chicoutimi, Saguenay, QC G7H 2B1, Canada
Ungarala Mohan Rao: Department of Applied Sciences, University of Quebec in Chicoutimi, Saguenay, QC G7H 2B1, Canada
Issouf Fofana: Department of Applied Sciences, University of Quebec in Chicoutimi, Saguenay, QC G7H 2B1, Canada
Patrick Picher: Hydro-Québec’s Research Institute, Varennes, QC J3X 1S1, Canada
Oscar Arroyo-Fernàndez: Hydro-Québec’s Research Institute, Varennes, QC J3X 1S1, Canada
Djamal Rebaine: Department of Applied Sciences, University of Quebec in Chicoutimi, Saguenay, QC G7H 2B1, Canada

Energies, 2023, vol. 16, issue 9, 1-23

Abstract: The degradation of the insulation system in liquid-filled power transformers is a serious concern for electric power utilities. The insulation system’s ageing is accelerated by moisture, acids, oxidation products, and other decay particles (soluble and colloidal). The presence of these ageing by-products is detrimental to the insulation system and may further lead to premature ageing and serious consequences. The ageing mechanisms of oil-paper insulation are complex, highly interrelated, and strongly temperature-dependent. The operating temperature of the transformer insulating system has a direct relationship with the loading profile. The major aspect that is witnessed with the fluctuating temperatures is moisture migration and subsequent bubble evolution. In other words, gas bubbles evolve from the release of water vapor from the cellulosic insulation wrapped around the transformer windings. The models presented in the existing standards, such as the IEC Std. 60076-7:2018 and the IEEE Std. C57.91:2011, are mainly based on the insulation temperature, which acts as a key parameter. Several studies have investigated the moisture dynamics and bubbling phenomenon as a function of the water content in the paper and the state of the insulation system. Some studies have reported different prototypes for the estimation of the bubble inception temperatures under selected conditions. However, there are various attributes of the insulation system that are to be considered, especially when expanding the models for the alternative liquids. This paper reviews various evaluation models reported in the literature that help understand the bubbling phenomenon in transformer insulation. The discussions also keep us in the loop on the estimation of bubbling behavior in alternative dielectric liquids and key attributable factors for use in transformers. In addition, useful tutorial elements focusing on the bubbling issue in transformers as well as some critical analyses are addressed for future research on this topic.

Keywords: transformers; insulation; bubbling; moisture; mineral oil; ester liquids (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2023
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (2)

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