Abstract
The characterizations of grounding systems subjected to high impulse conditions are known to be dependent on the polarity, current to peak time and discharge time, as well as the electrical properties of the soil, and the grounding electrodes themselves. It is therefore important to investigate the behavior of grounding systems under high impulse conditions under negative impulse polarity, and compare it with positive impulse polarity results. Experimental test results for the same grounding systems installed with various earth electrodes at several sites under positive impulse polarity have previously been presented. In comparison, this paper presents the results of negative impulse polarity injected on the same grounding systems. It is found that a significant difference between positive and negative impulse polarities is observed for the grounding systems installed at high soil resistivity.
Highlights
Impulse polarity has been known to affect the performance of many dielectric materials, such as oil, gas and solid insulators [1,2,3,4,5], as well as other materials, namely conductive water [6,7,8], soil or grounding systems [9,10,11,12,13,14,15,16]
This paper presents the results of experimental work performed on six earth electrodes, installed at three field sites under negative impulse polarity, which are compared to the results for positive impulse polarity presented previously in [17]
3 are presented in [16], wherewhere it wasit found that earth electrodes subjected to negative impulses had higher impulse impulse was found that earth electrodes subjected to negative impulses had higher Zimpulse than Zimpulse subjected to positive impulses for for earth electrodes with high
Summary
Impulse polarity has been known to affect the performance of many dielectric materials, such as oil, gas and solid insulators [1,2,3,4,5], as well as other materials, namely conductive water [6,7,8], soil or grounding systems [9,10,11,12,13,14,15,16]. A notable photographic observation was performed by Cabrera [10], who obtained the photographic information of sand discharges when subjected to DC and impulse conditions It was observed in his study [10] that under positive applied DC, the streamers propagated from the high voltage electrode to the ground, and vice versa when the applied voltage was under negative polarity. Given that the large percentage of lightning strikes in Malaysia consist of negative polarity, which is known to cause a higher breakdown voltage for electrical applications, it may not be advantageous for the grounding systems to have a high breakdown voltage and a lower current being discharged to the ground under negative impulse polarity. PEER and REVIEW time of positive impulse polarity for earth electrodes installed at high soil resistivity (site 2)
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