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Investigation on air + CO2 gas mixtures under lightning impulse

Masri, Muhammad Zakhwan (2017) Investigation on air + CO2 gas mixtures under lightning impulse. Masters thesis, Universiti Tun Hussein Onn Malaysia.


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This project aims to investigate the breakdown level of gas mixtures (air + CO2) under lightning impulse. Specifically, this project also reveals the breakdown characteristics of air, carbon dioxide (CO2) and the gas mixture (air + CO2) with the purpose of making a comparison. The gas mixture has a ratio of 70% of CO2 and 30% of air. These gases were tested inside the pressure vessel and subjected to 1 bar (abs) pressure. Standard (1.2/50 μs) lightning impulse was applied alongside with three electrode arrangements. The gap distance between electrodes is also varied ranging from 0.5 cm to 2 cm. It was found that highest U50 was recorded at the furthest gap length and when the insulating medium used was CO2. The rising trend of U50 is more obvious at sphere gaps as it provides more uniform fields. This U50 was calculated by using up and down method. Moreover, the highest maximum electric field (Emax) was found at non-uniform field gap namely rod-sphere gaps whereas the values were obtained with the help of FEMM simulation software. The Emax of rod-sphere when the air is used as an insulating medium has revealed that it is directly proportional to the gap length in which probably due to the self-restoration of air at the non-uniform field is less compared to other gas hence causing the dropoff insulation strength. As the gap distance between electrodes is small, the highest field utilization factor was recorded which is 0.93 (5 cm sphere), 0.86 (2 cm sphere) and 0.11 (rod-sphere) as a result of the field dispersed uniformly at short gaps. It was also noticed that the Emax is inversely proportional to the field utilization factor (η) whereas the risen of η has a huge impact to the value of Emax. However, this project is restricted to normal room temperature (26° Celsius) and no humidity factor is considered.

Item Type: Thesis (Masters)
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK2000-2891 Dynamoelectric machinery and auxiliaries
Depositing User: Mr. Mohammad Shaifulrip Ithnin
Date Deposited: 02 Aug 2017 09:06
Last Modified: 02 Aug 2017 09:06
URI: http://eprints.uthm.edu.my/id/eprint/9219
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