Any transformer should have atleat four earthings.
2 connections for its neutral earthing and
2 connections for its body earhtings
All the connections should be with dedicated earth pits 
which may be interconnected for relaiblity and to have 
lower earth reistance value.
These earth pits should be duly marked and to be tested on 
a dry day once in year of earth reisistance and earth 
continuity. Earth Resistance value should be less than 5 
ohms and if it is greater then these earth pits should be 
treated to bring dowun the value.

along with above said earthing thransformer bushing is also 
earthed which is mandatory

Any electrical  parameters have 2 Earthins 

: 2 Neutral Earthing

: 2 Body Earthing

Any electrical  parameters have 4 Earthins 

: 2 Neutral Earthing

: 2 Body Earthing