On the experimental determination of the nitrogen content of thermally upgraded electrical papers

Rodriguez, Esperanza; Jalbert, Jocelyn; Duchesne, Steve; Arroyo, O. H.; Rodriguez, Lidia B.; Cross, James G.; Lewand, Lance

doi:10.1109/tdei.2017.006792

Cited by 1 publication

(1 citation statement)

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“…There is a need for further investigation into bubbling phenomena in mixed oils, silicon oils, and natural esters (regenerated or reclaimed oil). These fluids are less expensive than ester fluids and have superior electrical, dielectric, and operational characteristics than mineral oil [90][91][92][93][94]. Furthermore, exploring ester admixtures in mineral oil for the bubbling phenomenon could lead to better insulation system performance at higher temperatures; -Mathematical modeling of bubbling inception temperature in alternative fluids: theoretically, no research has reported an exact equation for bubbling inception temperature in esters.…”

Section: Challenges and Perspectivesmentioning

confidence: 99%

Bubbling Phenomena in Liquid-Filled Transformers: Background and Assessment

et al. 2023

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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.

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