Effect of Floating Metallic Particles in Pre-Breakdown and Breakdown Characteristics of Oil Transformer under DC Voltage

I Made Yulistya Negara,Muhammad Novis Ibrahim,Daniar Fahmi,Mochammad Wahyudi,Dimas Anton Asfani,I G N Satriyadi Hernanda

doi:10.3390/en14123669

I Made Yulistya Negara, Muhammad Novis Ibrahim + Show 4 more

Open Access

https://doi.org/10.3390/en14123669

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Abstract

Contaminants in transformer oil insulation can float when meeting several conditions. Then, the presence of floating contaminants affects the electrical characteristics of oil insulation. Therefore, the pre-breakdown (corona) and breakdown characteristics due to metallic floating particles in transformer oil insulation would be investigated. This test used DC high voltage stress. A 56 Ω resistor was connected to the oscilloscope to detect the corona currents. The camera was used to capture the images of corona light emission. In addition, the electric field between the electrode and particles was simulated. The variables were the particle size, including its shape, and the distance between the particles and the grounded electrode. The experimental results show that the average value of corona inception and breakdown was inversely proportional to the size of floating particles. The peak value of corona current was directly proportional to the particle size. The lowest breakdown voltage was found when the particle was close to the electrode, but they were not in contact.

Highlights

Insulation serves as a separator between conductors with non-energized parts, or between two or more conductors with different voltages
A research group actively investigated partial discharge activity on flowing trans-former oil contaminated by metallic particles under different operating temperatures, velocity, applied voltage, and particle concentration [11,12,13,14]. They found that the metallic particles increased partial discharge activity and lower breakdown voltage, but moving oil helped reduce partial discharge activity
This study used a DC high voltage generator to test the effect of floating metallic particles on pre-breakdown and breakdown characteristics of transformer oil

Summary

Introduction

Insulation serves as a separator between conductors with non-energized parts, or between two or more conductors with different voltages. A research group actively investigated partial discharge activity on flowing trans-former oil contaminated by metallic particles under different operating temperatures, velocity, applied voltage, and particle concentration [11,12,13,14]. They found that the metallic particles increased partial discharge activity and lower breakdown voltage, but moving oil helped reduce partial discharge activity. The effect of floating metal particles in SF6 gas was investigated by using DC high voltage [20]. The variations of particle parameters, including location, size, and shape, were presented

Breakdown Mechanism and Corona as Pre-Breakdown Phenomenon

Experimental Setup of Oil Insulation Testing with Floating Metallic Particles

Corona Current

Unsymmetrical Particle

Symmetrical Particle

Conclusions