الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
In this work the needles in multi-needle configuration take different configurations such as line configuration with 3, 5 and 7 needles, triangular configuration with 4, 7 and 10 needles, square configuration with 5, 9 and 13 needles, pentagonal configuration with 6, 11 and 16 needles, hexagonal configuration with 7, 13 and 19 needles and square mesh configuration with 9 and 25 needles.
Also the onset voltage is measured in the laboratory and calculated based on the criterion of self-recurrence of electron avalanches growing in the vicinity of the needles when stressed negatively. This calls for calculating the electric field in the vicinity of the needles using the charge simulation method.
The calculated onset voltage values for all investigated configurations, indicate that the corona onset voltage of line and square mesh configurations take a trend, which is different from that of corona onset voltage of the triangular, square, pentagonal and hexagonal configurations. It has been shown that the calculated onset voltage decreases with the increase of the number of needles for triangular, square, pentagonal and hexagonal configurations, whereas it increases with the increase of the number of needles for the line and square mesh configurations. The calculated onset voltage values agreed reasonably with those measured experimentally and are in agreement with previous findings.