WHAT ARE FUSES USED FOR?

Fuses serve two main purposes:

1. To protect components and equipment from costly damage caused by overcurrents.

2. To isolate sub-systems from the main system once a fault has occurred. Also, please refer to ‘Can I replace a fuse with a circuit breaker?’in this section.

CAN I REPLACE A FUSE WITH A CIRCUIT BREAKER?

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.