Electrical Unbalanced Problem In Individual Equipments Terminal Box

How unbalanced is unbalanced?

If you have multiple single phase loads you should be attempting to balance out the transformer phases by spreading the single phase loads across the three different phases. If the transformer load is too unbalanced then transformer output voltage sag may result or the transformer may overheat (if you are exceeding the individual phase transformer current rating) degrading its life.

Yes unbalance current will effect the M/C life in the long run and if any phase current cross its max it may effect M/C immediately.Check once again your line voltage and harmonics levels are with in the limits.

Thanks,

We have throughly checked harmonic level and voltage which are perfectly with in limit.only problem is each equipment draws unbalanced current through electricity power but when we run the same equipment through D.G load,there is no problem,all the phases are taking equal current.

Check the neutral point(Star point) of Tr secondary it may be loose connection between Tr connection to earth pit or Tr connection to change over switch(neutral only) or Earth pit may be dried out.Mostly these are the causes, after checking revert back to me.

All the best

M.Ayyavaru.

Maybe using thermographic imaging will help you point out loose connections in feeders and bus's as well as terminal points.

Thanks for your comments...same test also carried out but nothing wrong in the busduct and cable connection...

Regards,

Ganesan.l

Thank you so much for your reply.

This basic things all are done..inaddition to earth pit testing and system audit.

It seems some peculier problem which could't find by audit also..

Let's working for transformer whole testing ....hopefully we will get some result..

Hi Yogesh,

When loads are run by Tr. unbalance distribution of current in phases observed; but when the loads are run by DG set no unbalance of current in pheses observed.

So, please check the current thro' the neutral in both the cases and for the same load condition you will probabely find higher neutral current when run by DG. There is loose connection between neutral to ground. Pl. start checking neutral connection from inside of the Tr. upto ground at different junction points.

For unbalance current in different phases of Tr. negative sequence component of current will generate and it is very much harmful for the Tr. run under this condition. The heating effect of negative sequence current is nine times higher than original sequence(positive sequence). Therefore, if the % of unbalance is substantatial, the % percentage of generation negative sequence current will also be high. It is observed that per 8 to 10 degree celcius rise in temp. with respect to designated temp. class of insulation, the life of insulation is becoming half. Therfore, if the Tr. is run with high % of unbalance currents in phases, the there may be failure of insulation due thermal ageing and ultimately the Tr. may be damage.

Regards,

Manindra.