The primary winding of a power transformer should always be

fused and input side and monitorized

The primary winding of a power transformer should always be "DELTA" connection.

the depnad upon the type of Transformer.
Distrinution Transformer connection .The primary winding of a power transformer should always be Delta Connection.
Delta Connection used for Three Phase Star Connection Used for Three Phase + Netural Line.

Fused..
When the secondary loaded is over loaded, it means draws max.
Current in the primary side due to which damaged the primary side as wellas appliances.
So that power t/f is fused the circuit.

That is not enough inputs to reply.
However,

the incoming side.

Delta connected

fused and input side and monitorized

The primary winding of a power transformer should always be the first coil in which the electric energy is fed from the a.c.
supply mains, and is called the PRIMARY windings and the other from which energy is drawn out is called SECONDARY winding.
A transformer is a device that,1.
transfer electric power from one circuit to another,2.
it does so without a change of frequency3.
it accomplishes this by electromagnetic induction and4.
where the two electric circuits are in mutual inductive influence of each other.5.
if N2 > N1 ie.
k >1 then transformer is called step up transformer6.
if N2 < N1 ie.
k <1 then transformer is called step down transformer.7.
ideal transformer input VA = output VA.
V1 I1 =V2 I2 N1= number of turn primary and V1 = Voltages in primary N2= number of turn secondary and V2 = Voltages in secondary.

The primary winding of a power transformer should always be Fused :)