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Current Unbalanced

07/29/2012 12:25 PM

How do I know Which one is producing an unbalance current?the generator side or in the load side (subswitchboard).If considering that generator side current measured to a Delta transformer going to the load side is unbalance(Primary) and the load(Secondary) side is reading inbalance phases too? Is there a means that i may be able to find out If my generator is producing the unbalance current or Is it coming from the load side?

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#1

Re: Current Unbalanced

07/29/2012 10:02 PM

The Out of Balance is coming from your load\distribution.

Any single phase devices and to which phase they are connected will determine the source of the out of balance.

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Sapper

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#2

Re: Current Unbalanced

07/29/2012 10:33 PM

load side only

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#3

Re: Current Unbalanced

07/30/2012 4:03 AM

Before it changed away from red/yellow/blue to whatever it is now, the red phase in most distribution boards was the one with the most current. The reason is that when electricians are asked to hook up new loads to an existing dis-board, they start naturally from top-left.

The solution is to re-allocate some of the red-phase loads onto the yellow and blue phases at the dis-board.

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#4
In reply to #3

Re: Current Unbalanced

07/30/2012 5:53 AM

Excellent anecdotal observation Slack.. Noted.

You've described normal load balancing there. All good but I think the OP wants to know how to test for imbalance.

You know if your load is unbalanced if the loads are not balanced.

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#5
In reply to #4

Re: Current Unbalanced

07/30/2012 8:12 AM

More anecdotal replies are probably overkill, but here goes.

Analysis of load connections, particularly added loads, ( like Slack noted so well) and analysis of potential loads versus connection layout (like Wal noted so well) will only take you so far. Often the real answer will revolve around actual load timing. If you have resistance loads early, and motor loads later, you may experience large unbalanced loads at distribution, no matter how carefully someone laid out the panel using equipment load specs. I am sure others can provide you with guidelines for identifying good practice when dealing with nuisance load imbalance.

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#6
In reply to #5

Re: Current Unbalanced

07/30/2012 8:36 AM

Duty cycles aren't always compliant.

Everything is nicely balanced when everything is running and then things start turning on and off as they deem themselves. 3ph loads take care of that but its all those pesky single phase branches that have you doing a shuffle.

I'm not sure if this is helping OP.

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#8
In reply to #6

Re: Current Unbalanced

07/30/2012 9:40 AM

I'm guessing this is not helping OP, so I'll post direct to you. I work with engineers most days. Your comment about duty cycles not being compliant is golden! This OP could be a genuine reflection of non compliant demand cycles created by non compliant people who are consuming energy in a non-compliant way, and adversely affecting a compliant duty cycle designed system. We see it regularly.

Now I will show my ignorance. Could this condition affect PF? Thanks Wal.

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#7

Re: Current Unbalanced

07/30/2012 9:32 AM

The only way the generator can be responsible for a current imbalance is if it has a bad winding and thus producing imbalanced voltage. Remove the load, Add back in a known good balanced simple load such as a 3 phase resistance heater, run the generator and if the voltages are balanced, then the problem lies on the load side. This is assuming a 3 phase generator by the way.

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#9
In reply to #7

Re: Current Unbalanced

07/30/2012 10:41 PM

That's a pretty good "how to" for the OP.

This is assuming a 3 phase generator by the way. Think about this...if it wasn't polyphase then there'd be no unbalance.

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JRaef (1); PFR (2); PWSlack (1); rishikathirasan (1); Sapper (1); Wal (3)

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