3 phase transformer system with separation of loads.

[INGMRS]

Hello Sirs

A customer has asked me to separate the loads in a building that feeds a bank of transformers with delta secondary configuration.

You want to send a three-phase configuration of 120/240 V from the transformer bank to another building with an electric meter, and you also he wants to send from this bank of transformers, power to another building, but in this case, with configuration 120/240 / 208V (High Leg), with another electric meter.

Here is my question:

Somebody has literature about how to calculate the desbalance of loads in the grup of transformers, due to the high leg of 208V.

Thanks in advance.

 

[Julius Right]

For the beginning try this:
https://en.wikipedia.org/wiki/High-leg_delta

 

[INGMRS]

For the beginning try this:
https://en.wikipedia.org/wiki/High-leg_delta

Thanks,

Here is my answer.

"In cases where the single-phase load is much greater than the three-phase load, load balancing will be poor. Generally, these cases are identified by three transformers supplying the service, two of which are sized significantly smaller than the third, and the third larger transformer will be center tap grounded. One of the phase-to-neutral voltage (usually phase "B") is higher than the other two. The hazard of this is that if single phase loads are connected to the high leg (with the connecting person unaware that that leg is higher voltage), excess voltage is supplied to that load. This can easily cause failure of the load.
Commonly there is a high-leg to neutral load limit when only two transformers are used.^[6] One transformer manufacturer's page suggests that High-leg to neutral loading to not exceed 5% of transformer capacity^"