The Formation Characteristics of Bubble in Oil-Paper Insulation and its Effect on the Breakdown

Zhao, Tao; Cheng, Xiangrui; Liu, Yunpeng; Wang, Fochi; Lv, Fangcheng

doi:10.1109/icd.2018.8514622

Cited by 5 publications

(5 citation statements)

References 9 publications

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“…Equations (1) and (2) provide another key clue as to how bubbles form. Noting that the denominator in the equation is r, it becomes clear that a bubble cannot be formed from nothing, (the pressure gradient would need to be infinite when r = 0) resultantly bubbles tend not to form in the bulk oil instead they typically form at surface impurities or interfaces [11,16,17]. For bubbles in transformers, the solid insulation acts as a trap for released vapour phase molecules which then accumulate and are able to form a bubble [18].…”

Section: Bubblesmentioning

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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Section: Bubblesmentioning

confidence: 99%

Analysing the power transformer temperature limitation for avoidance of bubble formation

et al. 2019

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“…Wang et al [17] conducted a study on the formation law of bubbles under different moisture content of transformer oil-paper insulation, and found that the initial temperature of bubble formation reduced with the increase of moisture content of the insulating board. Gao et al [18] designed an experimental model to simulate the paper insulation structure between transformer windings to study the generation characteristics of bubbles, and found that the temperature change rate and the gas volume fraction in the system have a great influence on the initial temperature of the bubbles.…”

Section: Introductionmentioning

confidence: 99%

“…Wang et al. [17] conducted a study on the formation law of bubbles under different moisture content of transformer oil‐paper insulation, and found that the initial temperature of bubble formation reduced with the increase of moisture content of the insulating board. Gao et al.…”

Section: Introductionmentioning

confidence: 99%

The bubble formation characteristics of oil‐paper insulation and its influence on insulation performance

Zhang

Wei

et al. 2023

High Voltage

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Engineering experience shows that for transformers with long service life and serious moisture exposure, the inter‐turn paper insulation inside the winding will precipitate bubbles under the condition of electric field and conductor heating, which will endanger the equipment insulation. In order to explore the influence factors of bubbles formation in the moist insulating paper of transformers, based on the existing research on the influence of moisture content and gas dissolution in transformer oil, this study further considers the influence of air pressure (AP) and electric field and establishes an experimental platform to change the air pressure and electric field, thereby studying the formation characteristics of bubbles in oil‐paper insulation. The results show that air pressure and electric field can affect the initial temperature, volume, and shape of bubble formation. From 0 to −0.05 MPa for air pressure, the initial temperature of bubble generation decreased by 41°C, its maximum two‐dimensional projected area increased by 418.4% with more severe distortion, and the breakdown voltage decreased. When the AC voltage applied on the needle plate electrode increased from 0 to 10 kV, the initial temperature of bubble formation increased by 29°C, and the maximum two‐dimensional projection area increased by 336.6%.

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“…Moreover, the study results showed that a serial connection bubble between the plates might cause the flashover [15,16]. The AC breakdown test confirms that the bubble and the press-board fail due to the surface flashover [17,18]. The inhomogeneous fluid electric properties, free charge, and oil breakdown due to the collapse of a bubble in the electric field were discussed in [19,20].…”

Section: Introductionmentioning

confidence: 99%

Bubble migration characteristics in power transformer oil under coupled stresses of forced vibration and electrical field

Ladislas

Liu

et al. 2022

IET Science Measure & Tech

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The stresses existing in power transformers lead to the generation of bubbles. They are the primary source that worsens and leads to insulation failure. Due to the complexity of bubble dynamics, it is challenging to figure out bubble mechanisms. However, creation, migration, and accumulation mechanisms require further explanation. A set of experiments has been conducted to provide a scientific overview of bubbles. The results revealed that buoyancy is dominant in low electric fields, while high electric fields affect bubbles' rise. Bubbles stretch and oscillate while moving. When the electric field is not strong, the AC field reduces the duration and volume of bubble detachment. Vibration stress on the other side is leading the bubble motion including detachment frequency and migration speed. Under the combination of AC and vibration stresses, the bubble distortion degree aggravates and bubble gathering formation is easy. This research can provide a deeper acumen of the bubble's actions beneath a power transformer under a combination of vibration and electric fields. It provides essential technique parameters to deal with while investigating bubble's problems and related engineering research areas.

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The Formation Characteristics of Bubble in Oil-Paper Insulation and its Effect on the Breakdown

Cited by 5 publications

References 9 publications

Analysing the power transformer temperature limitation for avoidance of bubble formation

Analysing the power transformer temperature limitation for avoidance of bubble formation

The bubble formation characteristics of oil‐paper insulation and its influence on insulation performance

Bubble migration characteristics in power transformer oil under coupled stresses of forced vibration and electrical field

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