Why the voltage unbalance is caused?

Question

I under stand that primary reasons are Unbalanced distribution of single-phase loads such as lighting or UPS or Heavy reactive single-phase loads such as welders etc.

But in a full fledge running system how to analyse that whether the voltage unbalance is due to unbalanced load OR unbalanced current is due to unbalanced voltage? b'coz 3 phase motor is a balanced load. when we supply a unbalanced voltage, it will draw unequal current resulting in more unbalanced voltage.

Answer 1

The analysis is done by a power quality meter. These are relatively inexpensive although you may consider that its cheaper to pay someone to come in and do the "one off" checks rather than buy the meter especially if you do not have skilled personnel to safely connect and use it.

You are correct with your understanding about where most of the issues may come from and, in most cases, there is not an problem because the single phase loads make up a small percentage of the total.

I would ask what makes you concerned you have an issue.

A bigger concern than unbalance may be harmonics.