The Influence of Heat Transfer Coefficient α of Insulating Liquids on Power Transformer Cooling Systems

This study presents findings on the influence of gap length distance on the lightning impulse breakdown voltage of three dielectric liquids of different chemical origins. The liquids were tested in a model electrode system with a quasi-uniform electric field distribution and a pressboard plate placed on the grounded electrode. The experimental studies were supported using calculations and simulations to show the individual relationships between the lightning impulse breakdown voltage and gap distance, which represent the so-called volume effect of the most stressed liquid. The results of the experiment, which involved four considered gap distances of 2, 4, 6, and 8 mm, show that a dynamic increase in lightning impulse breakdown voltage with an increase in gap distance is associated with mineral oil and bio-based hydrocarbons. However, similar trends were not observed for synthetic ester. Calculations that allowed us to assess the impact of gap length distance on lightning impulse breakdown voltage support the observations from the experimental studies. The curves obtained in this field can be considered in the process of designing insulating systems for transformers.

Section: Methodology Of the Studiesmentioning

confidence: 99%

Impact of Electrode Distance in a Quasi-Uniform Model Electrode System on Lightning Impulse Breakdown Voltage in Various Insulating Liquids

Kunikowski,

Rozga,

Pasternak

et al. 2024

“…The author studied the heat transfer coefficient α of insulating liquids also depending on various factors, such as the type of liquid (mineral oil, natural ester, synthetic ester), type of natural ester (standard, reduced viscosity), composition of the mixture (mineral oil-natural ester, mineral oil-synthetic ester, natural ester-synthetic ester), presence of nanoparticles (TiO 2 ), surface heat load q (1000, 2000, 3000 [W•m −2 ]), and the position of the heating element (vertical, horizontal) [25][26][27][28].…”

Section: Scope Of Tests Of Thermal Conductivity Coefficient λ and Hea...mentioning

confidence: 99%

“…The insulating properties have been quite widely recognized in comparison with the thermal properties [19][20][21][22][23]. The author has published many papers on the thermal properties of various insulating liquids [24][25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of Thermal Properties of Various Insulating Liquids Used in Power Transformers

Nadolny

2024

Self Cite

This article is a summary of many years of work by the author, in which the thermal properties of various types of insulating liquids, used in power transformers, were evaluated. Recently, esters have been displacing mineral oil. There is a common view that mineral oil has better thermal properties than esters. This claim is supported by comparative results of tests of both materials as a liquid only filling the remaining volume of the transformer. The effect of the type of liquid on the thermal properties of the paper–oil insulation has not been analyzed so far. On this basis, the conclusions formulated may be incomplete. For this reason, the author has analyzed the influence of the type of liquid on both the thermal properties of the liquid filling the remaining volume of the transformer and the paper–oil insulation. It was proved that the more effective liquid filling the remaining volume of the transformer was indeed mineral oil. On the other hand, a more effective electrical insulating liquid, which is an element of paper–oil insulation, is a natural ester. A comprehensive assessment that takes into account both the paper–oil insulation and the remaining transformer volume showed that the natural ester proved to be a slightly more effective electrical insulating liquid than the other analyzed liquids.

“…The authors' research shows that the coefficient α of an insulating liquid can have different values. They depend, among other things, on the type of liquid, as well as the temperature and length of the heat source [5].…”

Section: Introduction 1determination Of the Temperature Field In A Tr...mentioning

confidence: 99%

The Tools and Parameters to Consider in the Design of Power Transformer Cooling Systems

Goscinski,

Nadolny,

Nawrowski

et al. 2023

Self Cite

Transformers are the most important elements of electric power systems. Many conditions must be met for power transformers to work properly. One of them is a low operating temperature. This condition will be met if the transformer cooling system is properly designed. One of the components of a cooling system is insulating liquid. The heat transfer coefficient α of liquid determines its ability to cool the transformer. The higher its value, the more effectively the liquid transfers heat to the environment. This article describes the influence of the position of the heat source, which is usually in the windings of the transformer, on the coefficient α value of the insulating liquid. The vertical and horizontal positions of the heat source were analyzed. The coefficient α was analyzed at different points of the heat source. The tests were carried out for mineral oil and various esters. Heat transfer coefficient measurements were carried out for various surface heat loads of the heat source. It has been proven that, in the case of a horizontal heat source, the coefficient α has a value several dozen percent higher than in the case of a vertical source. It has been proven that the coefficient α has different values in different places of the heat source. Regardless of the location, the highest value of the coefficient α occurred in the lower part of the heat source.