How I can explain what's the purpose of the transformer tap is connected to ground?

Need some more info:

Why?

Center tap?
Any tap?

In a full wave rectification scenereo?
Power distribution?

Please explain a bit better.

Dear Sir,

The transformer tap (Star point) is connected to ground for following purposes:

1. In case of 3 phase neutral unbalance load, unbalance current should not remain circulation in other windings hence to give path to these currents and to maintain smooth supply voltage.

2. This neutral grounding provides a reference point for detection of earth fault in the system.