Fuses should be sized to protect the lowest ampacity component in the circuit. Electronic boards are damaged by voltage spikes, not by excessive currents that are not flowing through the boards. The TVS diodes are the protection from spikes. Glass fuses can get to be very expensive. I use breakers in line with fuses, the fuses having slightly higher amp ratings than the breakers and intended to be backup protection. I have never had a fuse blow--the breakers open first. I size the breakers based on the number of trains that might be operating on the particular channel (I use 6 TIU channels)
