[RFI] Electrical transfomer near shack, a problem?

[KD7JYK DM09]

"Should I be concerned about any RFI from the transformer's magnetic fields? 
If I locate the transformer further away I will have to use larger gauge 
wire to the house service entrance."

It really doesn't sound like a concern.  Magnetic fields won't interfere. 
Arcing can, if a field is strong enough, voltages induced into surrounding 
metal objects can arc, but this is quite rare.

Others may have more input.

Kurt