Circuit breakers have the advantage of being resettable and operationally
cheaper and they have certainly taken over the downstream protective
role where the potential fault currents are lower. So if you have a fuse in
a downstream role, then in some cases, YES you can replace it with
a circuit breaker.
However, due to their unique qualities, fuses are still required upstream in
the critical role. They are, in essence, the ‘gatekeepers’ of the protection
system. They are actually the most important protective device in the system.
Fuses have three unique characteristics:
1. They are safe. Modern fuses have extremely high breaking capacities –
can withstand very high fault currents without rupturing.
2. Properly applied, fuses prevent ‘blackouts’. Only the fuse nearest the fault
opens without upstream fuses (feeders or mains) being affected. Fuses can
provide selective co-ordination.
3. Fuses provide optimum component protection by keeping fault currents to
a low value… They are said to be current limiting.
So if you have a fuse in a critical upstream role. Then NO you cannot replace
it with a circuit breaker.