Moisture-bubbling of vegetable oil impregnated paper at transformer overload temperatures

Perkasa, C. Y.; Lelekakis, N.; Czaszejko, Tadeusz; Martín, D.; Saha, Tapan Kumar

doi:10.1109/icpadm.2015.7295212

Cited by 4 publications

(4 citation statements)

References 5 publications

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“…Here, crude glycerol contains 11.3 wt.% water that can be, in part, solubilized in the oily phase. In fact, a water solubility in a vegetable oil of around 0.9–1.8 wt.% can be estimated at 493 K from the correlations of Perkasa et al, and Hilder, . However, due to the fact that an inert flow is used during reaction, the water concentration in the oil is likely to be much smaller.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Edible Vegetable Oils Enriched with Healthy 1,3‐Diglycerides Using Crude Glycerol and Homogeneous/Heterogeneous Catalysis

Dosso

Luggren

Cosimo

2020

J Americ Oil Chem Soc

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Commercial edible vegetable oils in which part of their triglycerides are substituted with 1,3-diglycerides are healthier for human consumption than the original oils. This is because the human metabolism of 1,3-diglycerides is believed to occur through a distinct pathway with less probability of being deposited as fat in the body tissues. To obtain these enriched oils, conversion of triglycerides into diglycerides is carried out by glycerolysis using commercial crude glycerol containing dissolved alkali cations that homogeneously catalyze the reaction. The addition of a food production-compatible MgO as a supplementary solid basic catalyst, shortens the reaction time by half due to a combination of homogeneous and heterogeneous catalysis processes. In either homogeneously or homogeneousheterogeneously catalyzed glycerolysis, the increase of the reaction temperature in the range of 453-493 K increases the final 1,3-diglyceride content. Furthermore, in both glycerolysis processes the triglyceride content can be decreased in more than 60% with the consequent increase of total diglycerides to 50%, 70% of which are the 1,3-isomers. The glycerolysis reaction proceeds without altering the fatty acid distribution of the original oils.

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Section: Resultsmentioning

confidence: 99%

Synthesis of Edible Vegetable Oils Enriched with Healthy 1,3‐Diglycerides Using Crude Glycerol and Homogeneous/Heterogeneous Catalysis

Dosso

Luggren

Cosimo

2020

J Americ Oil Chem Soc

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“…It is well reported in literature that in order to generate a bubble the pressure balance equation shown in (1) must be satisfied [12][13][14][15][16].…”

Section: Bubblesmentioning

confidence: 99%

“…It is well reported in literature that in order to generate a bubble the pressure balance equation shown in (1) must be satisfied [12–16].

p_{int} = \frac{2 σ}{r} + p_{ext}

where p int is the internal pressure, p ext is the external pressure, r is the bubble radius, and σ is the surface tension of the oil–bubble interface.…”

Section: Introductionmentioning

confidence: 99%

Analysing the power transformer temperature limitation for avoidance of bubble formation

et al. 2019

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Failure of a transformer is a costly incident which can impact power system operation and result in loss of supply to customers. Transformers can fail through a number of mechanisms, one of which is from the formation of bubbles within the insulation. Currently, the loading guidance is set to avoid certain overload temperatures as high temperature is the main cause of bubbles forming. This paper analyses the limit set within the loading guides, comparing the most commonly cited temperature limit of 140°C with values taken from across the full spectra of available studies in literature. It is concluded that there is sufficient evidence for further investigation into formation of bubbles from transformer insulation as employing a single temperature limit may be inadequate. Use of a single temperature value is unsuitable, given the wide range of potential scenarios that the transformer fleet can present. It has become the go-to rationale that the moisture content of the solid insulation is the key driver for transformer bubbling temperature. This is true, however, it is shown that other factors such as solid insulation aged condition (determined through degree of polymerisation value) and the insulation type are also important considerations.

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“…One impact is that if the winding temperature of a transformer exceeds a certain threshold, bubbles of water are ejected from the paper insulation causing the dielectric failure of the oil gap. This phenomenon has been investigated in detail by several researchers [3] - [7]. In general, as the temperature of cellulosic insulation rises, the vapor pressure of the adsorbed water increases.…”

Section: Introductionmentioning

confidence: 99%

An investigation into improving the measurement of the water content of transformer electrical insulation

Martín

Saha

Hockey

et al. 2017

2017 IEEE Innovative Smart Grid Technologies - Asia (ISGT-Asia)

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Direct and indirect techniques are available to measure the water content of the cellulosic insulation of a power transformer. The measurement of the water content of cellulose is necessary because if it becomes too high, bubbles of water will be ejected from the cellulose insulation which may cause failure. Taking a sample of oil for Karl Fischer titration analysis is a simple and cheap laboratory based method to estimate the water content of the cellulosic insulation. However, it has been suggested in an IEEE Standard that errors of up to 200 % can be present. Due to a utility often operating a large number of power transformers, it is not practical to use better online methods (due to installation costs) or dielectric response (having to disconnect the unit) to monitor water content in a financially constrained economy. Therefore, a field study was performed to investigate how to improve the accuracy of determining the water content of paper using the traditional Karl Fischer titration method.

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Moisture-bubbling of vegetable oil impregnated paper at transformer overload temperatures

Cited by 4 publications

References 5 publications

Synthesis of Edible Vegetable Oils Enriched with Healthy 1,3‐Diglycerides Using Crude Glycerol and Homogeneous/Heterogeneous Catalysis

Synthesis of Edible Vegetable Oils Enriched with Healthy 1,3‐Diglycerides Using Crude Glycerol and Homogeneous/Heterogeneous Catalysis

Analysing the power transformer temperature limitation for avoidance of bubble formation

An investigation into improving the measurement of the water content of transformer electrical insulation

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