Ground to Neutral Voltage-Limit

A

Thread Starter

ASHUTOSH KUMAR

Dear ALL,

i am a C&I engineer with renowned poer group and our DCS is get failure repeatedly on 3-4 month which causing a huge almost 4 crore loss to my company. when i checked found

Ground - Neutral = 104 vac
Phase - Neutral = 224 vac
Phase - Ground = 124 vac

When i asked to my electrical personal about this they said the UPS supply used to be floating voltage (ie G-N=104). so kindly suggest me the ideal condition for this system as workstation motherboard and others are the frequently getting Damaged in my plant which causing a huge loss to my company.

<b>Moderator's Note:</b> Fixed as many misspelled words as I knew. Left the others alone.
 
Try to short your Neutral to Ground.

In the UPS distribution panel, short Neutral line to ground (easy way is if you have a spare breaker available, terminate single wire from your Neutral pole of MCB to ground or earth bar with in the panel and ON the breaker).

Hope it helps. Reply if it works.
 
W
You have not supplied enough information to help you. Some of the information that would be helpful would be:

1.. What kind of power system do you have, e.g. single phase, 2 phase, 3 phase, etc.?

2. How is your system grounded? Or is the output floated? IEC Type TN?

Strange voltages are many times caused by an ungrounded system or a cross connected systems. If your system is 120 VAC, the neutral should be grounded at the derived source or the first panelboard downstream thereof.

3. Your e-mail indicates that this may have started about 4 months ago. What changes to your UPS power system were made just prior to that time?

4. Has this happen before?

5. Is this a new installation?

6. Have you checked the voltages at utilization equipment?

7. What other electrical related problems are you having?

While your voltages are not quite correct ,it would appear that the "neutral" wire is actually a power (phase) wire (measuring across two wires and you get a significantly higher voltage than to phase to ground voltage generally implies both wires are hot and not the same phase). I would recommend that you review the UPS manufacturer's output wiring and grounding requirements, compare to your wiring arrangement ,and conform to the manufacturer's requirements (within your national electrical code requirements).


William (Bill) L. Mostia, Jr. PE
ISA Fellow, SIS-TECH Fellow,
FS Eng. (TUV Rheinland)
SIS-TECH Solutions, LP

Any information is provided on Caveat Emptor basis.
 
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