High voltage fuse: it’s good if properly used!

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


  • Hey Jacques.

    Very insightful article.

    Too many people don’t understand the true uses of a high voltage fuse and I’m glad you explained to us in details.

    Oh, and how much would you consider the price of a transformer to be “OKAY”?

    Mark Derulo
    Wichita, KS

  • Most people who are not familiar with electricity don’t know that electrical fuses protect electrical circuits from over amperage, not over voltage. Every electrical circuit whether rated to handle a large shop machine or motor, is setup to handle specific amperage. Thanks for sharing very informative.

  • I knew that having your fuses replaced on a certain schedule is required for maximum potential. But I didn’t know that there were high-voltage fuses. I unfortunately had to change my transformer in my house last year, but that was due to flooding in the house. I’ll be sure to use high-voltage fuses in the future. Thanks!!

  • Coming back after a looong time to my first love of MV fuses, after reading these posts (and some others) , I wonder wether MV fuses still have a long future facing them.
    Which applications , usages, will still request fuses, and not be wiped out by breakers ?
    In which countries are they still widely used ?
    Is it easy to find spares ?

    It seems that all major manufacturers have progressively dropped these productions ? Are there any manufacturers covering the world and being able to deliver spares, if I specify their fuses in new projects ?
    I know it is a lot of questions, … any hint to any of them is welcome !!

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