Solving Transformer Issue with 160KVA SOCOMEC UPS

[baroomby]

I new here at the forums. I have a situation in an office building I'm handling. Just want to know if someone could help me out. Here's the problem:

3 units of 160 KVA SOCOMEC UPS connected to 3 units 200KVA 3 phase 4 wire 460V/380V transformer connected in parallel. Configuration is attached.

Now, when we try to connect a new 80 KVA UPS to the 200KVA transformers then add three more feeder lines, and put the three 160KVA UPS to the 400KVA transformer,one of the 200KVA transformer gets burned. Basically, we want to isolate an area because of harmonics, that's why we did this.

Just want to know the cause of this so as to prevent it from happening again.

 

[negitron]

This is the kind of thing I do for a living but I'm at work now and don't have time to analyze your setup right now. If no one else gets you going by the time I get home, I'll have a look into it. Email me the full-size version of the attached schematic but add the things you're trying to connect, both as a reminder to me and to supply additional information.

Off the top of my head, I suspect a load-balancing issue but that's little better than an educated guess.

EDIT: If you can, also label the diagram with relevant voltages and phase currents (including neutral and ground). And any additional information you think may be relevant.