Stressed Oil Volume Theory in Transformer Winding Corner Stress Analysis

Gabrić, Petar; Orešković, Ana; Kuprešanin, Vjenceslav; Mikulecky, Antun; Podobnik, Vladimir

doi:10.1007/978-981-15-5600-5_4

Cited by 2 publications

(3 citation statements)

References 3 publications

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“…There is another view on this issue, which states that increasing the liquid volume occurs when increasing the gap between the electrodes while maintaining a constant electrode surface. Both observations are valid for alternating voltage and impulse voltage and are known as the oil gap length effect, most stressed electrode area, or most stressed oil volume [24,25]. Due to the problematic determination of the most stressed volume/area, these two theories are rarely used in common design practice in the transformer industry.…”

Section: The Influence Of Gap Distance On Liquid Breakdown At Lightni...mentioning

confidence: 99%

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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

Energies

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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.

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Section: The Influence Of Gap Distance On Liquid Breakdown At Lightni...mentioning

confidence: 99%

“…However, the effect of dielectric liquid gap length is implicitly considered in transformer design principles using safety factors or stress curves. As an example, we can give the "Kappeler" or "Weidman" curves, which are commonly used in the transformer industry [25,26].…”

Section: The Influence Of Gap Distance On Liquid Breakdown At Lightni...mentioning

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

Energies

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show abstract

“…The SOV is typically calculated as the region in which the calculated electric stress values vary between the maximum value and the 90% of it. Nevertheless, a recent study [15] suggests that it is more accurate to define the SOV as the region of the space where the electric field is above the 70% of the maximum electric field. The latter is the criterion that will be adopted in further sections of the paper.…”

Section: E Breakdown In Large Oil Volumesmentioning

confidence: 99%

Dielectric Design of Ester-Filled Power Transformers: AC Stress Analysis

Montero

García

Burgos

et al. 2022

IEEE Trans. Power Delivery

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In the last 20 years the use of ester fluids as an alternative to mineral oil for transformer insulation has been an active field of research and development. These liquids have a much lower environmental impact than mineral oils, besides reducing the transformer's fire risk. Although the use of natural and synthetic esters is nowadays frequent for certain applications, as for distribution transformers in highly populated areas, railway transformers or off-shore windmill transformers, the experience on large and medium sized units is still reduced.One of the critical aspects that must be assessed to use esters as dielectric fluids for large size transformers is the dielectric design of the equipment. The permittivity of esters and esterimpregnated cellulose are different from those of mineral-oilcellulose systems, what has an impact on the electric field distribution in the transformer. Additionally, in some cases, the dielectric strength of ester fluids differs from that of mineral oil. This paper presents a study about the dielectric design of esterbased power transformers. The insulation system of a 400/138 kV, 280 MVA transformer was modelled using a finite element tool and a comparison of the field distribution under 50 Hz AC power voltage of both insulation systems is provided.

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Stressed Oil Volume Theory in Transformer Winding Corner Stress Analysis

Cited by 2 publications

References 3 publications

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

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

Dielectric Design of Ester-Filled Power Transformers: AC Stress Analysis

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