Study on dynamics of the bubble in transformer oil under non‐uniform electric field

Zhao, Tao; Liu, Yunpeng; Lü, Fangcheng; Rui-hong, DU

doi:10.1049/iet-smt.2015.0239

Cited by 13 publications

(8 citation statements)

References 24 publications

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“…Bubbles will decrease the electrical strength of the oil-pressboard insulation, and will cause a partial discharge in the oil, finally resulting in the insulation breaking down due to the accumulation of the bubbles. Therefore, the bubbles are a key factor that affects the breakdown voltages of the oil-pressboard insulation [4].…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Breakdown Characteristics of Transformer Oil Influenced by Bubbles

Qin

Shi

et al. 2018

Energies

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Bubbles will reduce the electric strength of transformer oil, and even result in the breakdown of the insulation. This paper has studied the breakdown voltages of transformer oil and oil-impregnated pressboard under alternating current (AC) and direct current (DC) voltages. In this paper, three types of electrodes were applied: cylinder-plan electrodes, sphere-plan electrodes, and cone-plan electrodes, and the breakdown voltages were measured in both no bubbles and bubbles. The sphere-sphere electrodes were used to study the breakdown voltage of the oil-impregnated pressboard. The results showed that under the influence of bubble, the breakdown voltage of the cylinder-plan electrode dropped the most, and the breakdown voltage of the cone-plan electrode dropped the least. The bubbles motion was the key factor of the breakdown. The discharge types of the oil-impregnated pressboard were different with bubbles, and under DC, the main discharge type was flashover along the oil-impregnated pressboard, while under AC, the main discharge type was breakdown through the oil-impregnated pressboard.

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Section: Introductionmentioning

confidence: 99%

Experimental Study on Breakdown Characteristics of Transformer Oil Influenced by Bubbles

Qin

Shi

et al. 2018

Energies

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“…The behaviour of gas bubbles in transformer oil under the alternating electric field has been studied in [13]. The investigations showed that bubbles can initiate partial discharge, and their development may alter an electric field in a stationary oil state [14]. Moreover, the study results showed that a serial connection bubble between the plates might cause the flashover [15, 16].…”

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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“…Although dielectric liquids are easy to implement in the insulating systems and provide electrical insulation effectively, they are very sensitive to impurities due to their specific chemical structure. In particular, pollutant materials within the structure such as solid particles [3,4], gas bubbles [5], or water droplets [6,7] greatly reduce the dielectric performance of insulating liquids [8]. There are many methods, such as, for example, the AC breakdown voltage and dielectric dissipation factor measurement, gas chromatography, and the determination of the moisture content in oil, which are used to estimate the condition of a given dielectric liquid [9,10].…”

Section: Introductionmentioning

confidence: 99%

Using the Method of Harmonic Distortion Analysis in Partial Discharge Assessment in Mineral Oil in a Non-Uniform Electric Field

et al. 2020

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In high-voltage equipment, it is vital to detect any failure in advance. To do this, a determination of the partial discharges occurring at different voltage types as well as at different electrode configurations is essential for observing the oil condition. In this study, an experimental setup consisting of a needle–semi-sphere electrode configuration immersed in mineral oil is prepared for laboratory experiment. In such a way, a non-uniform electric field is created and the leakage currents are monitored from the grounded electrode. A total of six different electrode configurations are analyzed during the tests by the use of hemispheres of different diameters as grounded electrodes and copper and steel pointed (medical) needle high-voltage electrodes. In the experiments, the partial discharges occurring at four different voltage levels between 5.4 and 10.8 kV are measured and recorded. The effect of the different electrode configurations and voltage levels on the harmonic distortion are noted and discussed. It is experimentally confirmed that it is possible to measure the leakage current caused by the partial discharges of the corona type in oil at the different metal points, creating high-voltage electrodes and different electric field distributions based on the proposed non-invasive measurement technique. The studies showed that there is a significant rise of even harmonic components in the leakage current during the increase in the partial discharge intensity with the 5th harmonic as dominant.

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Study on dynamics of the bubble in transformer oil under non‐uniform electric field

Cited by 13 publications

References 24 publications

Experimental Study on Breakdown Characteristics of Transformer Oil Influenced by Bubbles

Experimental Study on Breakdown Characteristics of Transformer Oil Influenced by Bubbles

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

Using the Method of Harmonic Distortion Analysis in Partial Discharge Assessment in Mineral Oil in a Non-Uniform Electric Field

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