3 Phase system (Electrical)


Thread Starter

Santanu Das

Say our distribution transformer is 11kv/415v...one of the three phase (LV) is coming in our flat/building. other two in nest buildings. say if one LV phase is out (fuse blown off) what will b the effect in the other 2 healthy phases and to the transformer. will the transformer continue to give load?

Again if one fuse of HV side is blown off (one phase is cut off) what will b the effect on lv side phases? please explain a bit.
I'll assume the transformer is configured delta-wye.

If you look at the picture on the Wikipage page referenced above - say that the fuse on primary 1 is blown. P2 & P3 will still be at full potential.

With P1 now floating, the P2-P1 winding and the P1-P3 winding are now in series. P1 will float to about half the normal voltage. Each of those windings will be approximately half voltage.

On the secondary side, S1 and S2 should be approximately 207 volts. S3 should be 415 volts.

Disclaimer - This is just based on theory; I've seen this in a powerplant but don't remember what the voltages were. I do know it wasn't good - a lot of devices burned up.