Explain the significance of let through energy when assessing discrimination between major and minor fuses in a system of feeder protection?

Answer 1

I2t is imoprtant to know if a fuse that protects a whole branch is going to blow before one of its ramifications. So it is important that the fuse protecting the branch has bigger I2t than the branch. Another important fact is that the fuse protecting the branch has to be 1.6 bigger than the max nominal value of the current in the branch European Rule Of Thumb