Generally single phase loads having transformers have the following type of fuse as main protection.

Better reliability can be observed in distribution system with

Sectionaliser can

The final operation of the recloser for a close in permanent fault is

Consider 5P20 class CT ratio:1000/1, Normal rated current of 900 A. Consider a overloading of 10 % while calculating plug setting of the relay with IEC SI curve. Let the initial set TMS be 0.1. Relay settings has ranges for PSM of 50% to 200% in steps of 25% and TMS setting range of 0.1 to 1.1 in step of 0.05. The operating time for a three phase fault of 15 kA is (Hint: Calculate PS, then calculate the operating time using the curve characteristics equation)