Current unbalance in 3 phase system but no neutral current

[Msingh15]

Hi All,

I have got this situation, we have put 2 PQ loggers on 240/415V distribution feeders. I am analysing the data from the loggers.

Looking at data, it is very apparent there is unbalance in system. Also these 2 feeders has got a lot of PVs connected to them (70% customers have PVs).

What my question here is when i looked at data that the neutral current value is not what i was expecting by looking at the unbalance?

I looked in to harmonics data and the 3rd, 5th and 9th order harmonics exist, please check attached photo.


the other logger's data was different, where the system was fairly balanced but due to 3rd,9th & 12th harmonics present, the neutral current was high, that made sense.

Any thoughts?

Thanks

 

[waross]

A line to line single phase load or a line to line single phase co-generation will cause an unbalance but will not cause a neutral current.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[argotier]

First we should separate both aspects of your problem, on one hand the current unbalance and in the other the presence of harmonics.

For the current unbalance part, as already said, not necessarily a phase current unbalance will result in a neutral current (only if the sum of the current phasors give you a non zero resultant).

Now, with the presence of 3rd harmonic and multiples, you should at least see a neutral current of about 3 times the 3rd harmonic.

Your attachment only gives us the harmonic spectrum for the phases, but what about the neutral measuring? What values are you getting exactly?

 

[Msingh15]

Thanks Waross.

Argotier,

In that attachment the neutral current is shown in pink color, it is low (2A).

I have now attached another attachment from second logger. The neutral current is about 22A and sum of 3rd harmonics of each phase gives about 23A in Neutral.

Thanks

 

[argotier]

In that attachment the neutral current is shown in pink color, it is low (2A).

Thanks, now I see it.

I would check all the measuring circuit, something is wrong.