Kent
The area from which (province of Ontario, Canada) used to supply (PUC's)[actually in some area's still do] based on a Delta system to all services that were based on 575 Volt services.
These usually were buildings of Industrial and larger commercial.
In my younger days, we had to install Delta/Wye auto transformers to drop down to the 120/240 or 120/208 voltages for the general loads.
Most of the PUC's today are converting their supply system to Wye.
I'm not a 100% sure but I believe that the reason is: If a building (on Delta)has a fault it could cause problems back up the supply line and affect other customers?
