ELEKTRIKA - UTM Journal of Electrical Engineering, Vol 13, No 2 (2011)

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Breakdown Mechanism for Small Airgap in a Sharply Non-uniform Field

John Tarilanyo Afa

Abstract


Townsend predicted a diffused form of discharge but in this study it was found that the type of breakdown for small air gap was the streamer mechanism. In order to establish the breakdown pattern of this gap distances the impulse voltage (1.2/50 µS) was used with the negative and positive point electrodes. The gap distances maintained were 1 cm, 2 cm, 3 cm and 5 cm. A kraft paper (0.25 mm) was placed within the gap of the electrode arrangement. On each test, holes were punched on the paper and their spreads were determined. For positive point electrodes, the discharges were irregular and filamentary while with the negative point electrode the discharges proceed in steps and no filamentary avalanches were observed. It was also observed that the negative breakdown voltages were about 1.5 – 2.0 times higher its equivalent positive point electrode. From all the tests it was confirmed that the breakdown mechanism was that of streamer mechanism.


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ISSN 0128-442

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