A recent article from Lothar presented a bad experience with fuses.

I would like to say that high voltage fuse remain a good solution, provided that they are used in a proper way.

Fuse-switch protection for MV/LV transformer is the most common solution, mainly because it is a cheap solution, compared to circuit breakers.

Of course high voltage fuse and circuit breaker don’t have the same behaviour when faults occur.

The advantage of the fuse is that it operates very quickly on high magnitude faults, much faster than circuit breaker that always has to wait for the order of a relay.

When the fuse is used within a switch fuse combination, it has to comply with specific standards, for example IEC 62271-105. The selection of possible fuses to associate with a switch is generally done by the manufacturer of the switchgear. That is why it is not recommended to try to use other types of fuses than those in the manufacturer list.

As many contributors wrote, in case of a fault, the first thing is to analyze what happened and clear the network from the problem. After that, it is mandatory to replace all the fuses at the same time and not only the one that blew.

It also must be considered that fuses age over the years, because of heating in the switchgear, possible corrosion of connections, inrush currents, overloads… So, it is wise to plan a replacement of the fuses before one is blowing without any real fault in the network or in the switchgear.

All this is work and time, but this is the way to ensure keeping the health of the installation, and as someone said, the cost is in any case less than the cost to replace a transformer!

Jacques CALERI