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http://dx.doi.org/10.5207/JIEIE.2011.25.5.067

Experimental Study of The Floating-Phenomenon on Neutral Ungrounded UPS System  

Shim, Hae-Sup (기상청 국가기상위성센터)
Publication Information
Journal of the Korean Institute of Illuminating and Electrical Installation Engineers / v.25, no.5, 2011 , pp. 67-72 More about this Journal
Abstract
In this study we investigate the background of UPS output transformer(${\Delta}-Y$) operation on neutral ungrounded system, and perform field experiment of neutral floating-phenomenon for the inter-locked securing of electric facilities and improvement of neutral floating-phenomenon. Experiment results show that a floating-phenomenon occurs when four-pole input-breaker trip and the neutral to earth voltage occurring concurrently is identified as phantom voltage. And the measures for the transient overvoltage that can occur in floating-state also are investigated. As a result, the risk elements of neutral ungrounded method as well as neutral floating-phenomenon are removed by installation of separate solidly-grounded transformer and switching four-pole input-breaker to three-pole input breaker.
Keywords
Neutral Floating-Phenomenon; Phantom Voltage; Transient Overvoltage;
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