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sunday matembo
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Join Date: Jan 2012
Posts: 24

Un Balance Voltage System

01/20/2012 8:44 AM

I gatta problems in electrical circuit esp. 110Vdc system in Power house which causes most of devices to burn out , When i measure voltage betweeen live phase and neutral it comes 110Vdc approx..but when i measure btn live phase to ground it comes 91V approx. instead of 55Vdc.It seems there issue in neutral phase maybe it get lost somewhere ....Could someone help me how to restore the lost neutral system ( i will love it)???? or anyother suggestion to troubleshoot this problem????.Maybe i might be wrong somewhere.

Rgds

sm
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KJK/USA
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United States - Member - Member Engineering Fields - Electrical Engineering - Electrical Construction

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#1

Re: UN BALANCE VOLTAGE SYSTEM

01/20/2012 9:17 AM

It seems that you have identified a viable issue.

My suggestion is grab your "meter" and have at it.

If this makes no sense to you consider hiring a professional to resolve the issue.

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PeterT
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#2

Re: UN BALANCE VOLTAGE SYSTEM

01/20/2012 9:21 AM

Please verify that we are talking about DC here? For DC you have Positive (+) and Negative (-), not phase and neutral (those are AC terms).

In an ungrounded DC system, the + and - will not be split evenly 50/50 above and below ground potential, mainly because of insulation resistance and leakage. The voltages will, however, be someplace near to that. In a 110VDC, you may see 60V on + and 50V on -, or something like that.

If you are seeing 91V on the +, you probably have an impedance ground on the negative. It is not solidly grounded, or you would have 110V on Pos and 0V on Neg. It is likely that there is someplace on the negative rail of the circuit where the insulation has been compromised. You need to do some searching to look for where wiring insulation has been damaged, contaminated, or bridged to ground. Good luck!

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cuba_pete
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#6
In reply to #2

Re: UN BALANCE VOLTAGE SYSTEM

01/20/2012 6:01 PM

He's stating live phase and neutral. If he doesn't grasp the conceptual differences of AC and DC...he has a long road ahead. Maybe another on-site electrician should provide some guidance...?
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sunday matembo
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#8
In reply to #2

Re: UN BALANCE VOLTAGE SYSTEM

01/21/2012 8:34 AM

Hey PeterT,,, u know i have two systems one 110Vdc to supply dc system to all componet which uses DC...eg.. several SUPERVISION CARDS,SOME RELAY,THYISTOR CONVER (SCR) ects this comes either from 110Vdc Battery bank direct or from AC/DC CONVTER means we takes some AC we convert to dc. Secondly , 48Vdc system which comes direct from 48Vdc battery bank but from this system we have no unbalance (means live phase to ground we get 24Vdc approx which is OK).

Rgds

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TonyS
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#9
In reply to #8

Re: UN BALANCE VOLTAGE SYSTEM

01/21/2012 12:59 PM

Without a fixed reference to earth you are never going to get a steady readings between + & - to earth.

At a guess the item that burnt out has an earth fault on it and was trying to provide an unintentional reference for everything else.

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PWSlack
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#3

Re: UN BALANCE VOLTAGE SYSTEM

01/20/2012 9:41 AM

What is the voltage rating of the devices that <...burn out...> and how are they connected to this system?

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Yahlasit
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#4

Re: UN BALANCE VOLTAGE SYSTEM

01/20/2012 11:30 AM

Honestly, it is the first time I hear about a DC distribution system, after Edison's ! Efficiency is something to discuss in another thread, but for now, here's my two cents. (assuming that by Power house you meant Power plant).

Regards

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PeterT
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#5
In reply to #4

Re: UN BALANCE VOLTAGE SYSTEM

01/20/2012 1:47 PM

Many electrical facilities (generating plants, transmission & distribution substations, etc.) have a DC distribution or station service fed from a battery bank for the majority of their protective and control functions, such as protective relays, breaker tripping & closing, SCADA, etc. There is an AC distribution system as well, which powers the battery charger, lights, house power, HVAC, etc. That way if the AC building service is lost, there is some time period (often 8 hours or more) that the batteries are sized to be capable of supporting all the critical functions of the facility.

These battery systems are usually operated ungrounded, so that a ground fault at any one point won't compromise their operation (similar to a 3-phase delta distribution system). The battery charger usually has ground fault detection built in, so that if a ground fault occurs, an alarm is sent to SCADA or other monitoring, and service personnel can come to isolate and correct the ground before a second one really takes the system out of operation.

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SolarEagle
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#7

Re: UN BALANCE VOLTAGE SYSTEM

01/20/2012 8:07 PM

It sounds like you have a shorted control component...If you know what the amp draw should be then you can trace it....otherwise it's trial and error

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cuba_pete (1); KJK/USA (1); PeterT (2); PWSlack (1); SolarEagle (1); sunday matembo (1); TonyS (1); Yahlasit (1)

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