Single Phase loads on 3-Phase High Resistance Grounded Systems

[bdn2004]

The transformer is 13.8kV - 480V, 2500kVA delta-wye HRG. Through a switchgear the transformer feeds balanced three phase loads i.e. motors and 3-phase step down transformers.

It is proposed to install a 100kVA, 480V - 120/240V single phase transformer on this system to feed an existing building. Since the HRG system has no neutral, will this affect the secondary voltage on the 2500kVA transformer? Why or why not?

 

[jghrist]

Since the transformer will be connected line-to-line, there should be no problem. There will be a phase unbalance because two phases will have more load, with some unbalanced voltage drop, but 100 kVA on a 2500 kVA transformer should present no problem.