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Topic Title: faults on low voltage networks (400V)
Topic Summary: whether the neutral impedance should be considered during fault calculation
Created On: 09 October 2012 05:31 PM
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 09 October 2012 05:31 PM
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SWORDLOVER

Posts: 23
Joined: 30 September 2010

As we all know, on networks of higher voltage levels than 400V, there is no neutral conductors generally. During the fault calculation, only phase impedance and transformer impedance are considered. However, for 400V networks, there is a neutral conductor. So when single-phase to ground fault happens, whether the fault current would flow through the neutral conductor, or through ground as the networks of higher voltage level. One more question, for 400V networks, what dose the single-phase to ground fault mean? It refers to the short circuit between one phase conductor and the ground or one phase and neutral conductor?
 09 October 2012 09:08 PM
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simongallagher

Posts: 148
Joined: 28 July 2005

Hi there,

Old LV cables had an earthed metalic sheeth, new LV cables have a combined earth and neuthral screen around the conductors, and HV cables have an earthed screen around the conductor, so not that much difference.

Simon
 09 October 2012 10:03 PM
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SWORDLOVER

Posts: 23
Joined: 30 September 2010

Thanks for your reply!

Do you mean that for both HV and LV networks, the fault calculation (calculation of the fault current) would involve the impedance of neutral or earthed screen?
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