What is meant by the "transfer current" for a fuse-switch combination?

Definition:
It is the value of current above which the fault current will be cleared by the three fuses only, the switch not having enough time to react.

Meaning/Impact:
This value must be observed in transformer feeder protection scheme in order to prevent the condition of fault clearing through the fuses only, this can be studied by knowing the below data:

• Fuse time-current characterisitcs (minimum melting time).
• Switch opening time.

The below graph illustrates the concept.

Released for:Schneider Electric United Arab Emirates