#1248 What does a fuse do?

What does a fuse do? A fuse is there to protect an electrical system from an overload by cutting off the power.

These days, we have multiple electrical circuits in our houses that operate numerous devices. Unless we have solar panels or our own generators, we get the power from an electricity power station. There will be multiple power stations around the country. Depending on the type of power station and its size, they can supply power to thousands of homes. A single megawatt of power can power between 500 and 1,000 homes. That is the equivalent of 4,000 solar panels. A typical coal-fired power station will produce 1,000 megawatts, which can power 800,000 homes. A typical nuclear power plant can produce a little more and power over a million homes. Once the power is produced, it has to be sent to your house. It is stepped up to a higher voltage first of all so that it can be transmitted along power cables. When the voltage is increased, the current is decreased, which means there is less heat loss as the electricity is transmitted and it is more efficient. Your houses is obviously pretty far from the power station and the transmission cable has to be long. Once the power reaches your neighborhood, it goes to an area transformer, where the voltage is stepped down. Then it goes along many cables, one of which comes to your house. It goes through a transmission box first, where it is stepped down again to be at a voltage level our house can use. Then you can plug your devices into the wall and make use of that electricity.

If all goes to plan, you will have no problem with your power and your devices. However, sometimes there can be a power surge. There can be many reasons for this. The power company could be transferring power between grids, and this can cause a sudden jump in the electric current. It could be caused by lightning hitting the electrical grid somewhere. Sometimes, when power is restored after a blackout there can be a sudden surge in current. It could happen if you have too many power-hungry devices on the same circuit, such as an extension cord. It could be caused by faulty wiring, which makes the current ebb and flow in surges. It could be caused by a short circuit, which is where the electricity from your power source finds a low-resistance route to return to the power source, bypassing the device you are trying to run. This produces a surge of current. You want fuses for when the power does surge.

There are many different types of fuses, and they are all rated for a certain amount of current, which is measured in amps. At its simplest, a fuse is two connectors with a strip of metal between them. This metal is usually copper or silver. When there is a normal current running through the circuit, the fuse does nothing. However, when the current gets higher than the rating of the fuse, the resistance through the strip of metal produces an enormous amount of heat and the metal very quickly melts. This breaks the connection in the circuit and the power switches off. If it didn’t switch off, it could cause damage to the devices you are using, or it could even be dangerous to you. Power surges, especially from short circuits, can cause heat, fires, and electric shocks. The fuse can save the system. Once the fuse has burned, it needs to be replaced. If the underlying problem hasn’t been fixed, the new fuse will just melt as well.

These days, you won’t find fuses in most modern homes. We use circuit breakers more often because they can be reset with a switch and don’t need to be replaced. Fuses are known as sacrificial devices because they die to protect you. A circuit breaker works on the same principle but without sacrificing itself. Each circuit runs past a switch that is set for a certain number of amps. If the current exceeds that number of amps, the circuit breaker just switches off, cutting the circuit. Sometimes it might be because you were using too many devices and switching either the kettle or the washing machine off will fix it. Restore the circuit breaker and things will be fine. If the circuit breaker trips again, you have a bigger problem on your hands. Don’t get angry, though, because the circuit breaker is probably saving your life.

The first fuse was introduced in France in 1864 to protect telegraph stations from lightning strikes. Thomas Edison patented them in 1890 to go with his electric grid. And this is what I learned today.

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Sources

https://www.dfliq.net/blog/electric-fuse/

https://www.eaton.com/gb/en-gb/products/electrical-circuit-protection/fuses-and-fuse-holders/fuses-faqs.html

https://en.wikipedia.org/wiki/Fuse_(electrical)

https://www.realpars.com/blog/circuit-breaker

https://solarschools.net/knowledge-bank/energy/electricity/flow