What exactly is the difference between a surge protector and a fuse? Can a fuse protect the electronic devices from lightning instead of surge protector?
Last Updated: 18.06.2025 19:48

This is a photo where a lightning bolt took out a home's complete mains distribution box, and a lot of electronic gear as well.
(There is no concept of polarity, in the loop because the current changes direction 100 to 120 times a second (power frequency).
Would individual surge supressors have save this equipment? most likely, since the surge supressor would take the jolt instead of the electronic components.
An AC voltage/ current source, and an ac inductive load.
Here is a simplified AC power diagram.
He then asserts :
a photo is worth a thousand words.
2024–09–27 [ Mohan Rajaratnam Mohan Rajaratnam ] . Thinks you can get free electricity from nothing : Mohan Rajaratnam's answer to Is it possible to generate free electricity at home using a magnet or other low-cost methods? If so, how does it work?
He then describes Rainy Season and Lightning.
The bolt then partially travels down the line to your home.
This one hit behind the barn.
so, what happens?
“ A fuse is a device which protects the (circuit) against overload and short circuit.”
2024–10–11 [Victor Olarewsju Victor Olarewaju ]
“ … to protect building, lightning arrestor, is provided above building and directly connected to earth.”
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These are simplified answers to the original question, and does not change anything I wrote above.
This is 'the assistant's answer'
[image of Common-mode choke]
A fuse is a non-resetable over current circuit protector.
2024–10–16 [ OO OLAOYE OYEBODE ]
The other is “what does a “fuse” do?”
what exactly is a ‘surge’ protector?
but this device (an Inductor) … impedes the rapid changes in the current.
(Dc diagram shown, AC is similar).
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But during the surge, the fuse will not blow if it is a longer duration and lower value )10 to 50%).
Edit 2024–10.
OK, this is Mohan Rajaratnam’s definition of a Surge suppressor.
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but I think this circuit , shows a few more pieces.
If the nominal power is 4,000 watts then the current at 230volts is 16 amps.
There is no harm in having the surge suppressor along with the fuse in the circuit. The fuse will not open up until the current melts the link. This will take time, and in the interim, that jolt will get transmitted into the power supplies.
So combined with a device called a MOV or Metal-oxide-resistor, then forms the 3rd part of a “surge suppressor “.
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2024–10–14 [Omar Gharbi Omar Gharbi ]
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This is where this question deviates from being a 'generic' question, and becomes more specific.
What does a fuse do?
It’s been three xxx five werks, and there has been no response to my follow on query on his Commment to my answer.
But it can get overloaded, and no longer works.
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There are three different concepts here that are getting confused.
2024–10–11 [Bobby Sanchez Bobby Sanchez ].
Upvotes:
Now when you have a certain ac resistance, then a current flows in a loop.
At one ohm, the resistor has a maximum of 1 watt power.
This is an electronic circuit designed to clamp voltages so that the Voltage Potential that appears at the outlet is never going to exceed the nominal value.
2024–10–00 [ Ammar Mahdi ] Ammar Mahdi
so, the loop of wire then, when put together with another loop reduces the ‘noise’ on a power line.
The MOV will conduct when the voltage exceeds 50% of line voltage.
[old diagram got deleted by accident]
So, the voltage could go up to 500 volts, and the fuse will not open up.
When the current is 200% of the rated value , it will “go open” (the link metal melts) and protect the device.
the problem then depends on "how fast does the fuse operate?".
For this case there are devices called Metal oxide varistors (MOV).
What is lightning?
Is the question then , "why buy a surge supressor, if the fuse alone protects the electronic circuits from a lightning bolt?".
This is a high voltage low current spike that comes down the line because of the power poles being struck, and the voltage suppressors activating on the primary side of the transformer.
It seems Mohan does not understand the difference between a comment and an Answer.
P = e* I, so since I is 16 amps, then the voltage dropped is 1/16 volt or 0.0650 volts.
He then describes the function of a fuse.
But… the neutral is now “floating” because of the 1 ohm resistance.
Barnstars:
Because the load is inductive, the current lags the voltage.(by a bit).
At the secondary, it is 1000 times less.)turns ratio). If it gets hit with a 100,000 volt bolt of lightning then the voltage arrestors conduct and clamp the voltage down to line voltage, ( but a small amount leaks down the line). This is the problem.
Mohan forgets that a fuse is a one-time device, and needs to be replaced if it is tripped.
Fuses, on their own, then operate much slower than the MOV variable resistance, during the lightning strike.
At least they know the answer if they wanted it.
These devices are installed between the “hot” and “neutral” and protective ground.
The third is lightning and “how it gets conducted into a home.”
There are two important concepts here.
First Sentence:
I post the exact comment here.
2024–10–10[John johnson John Johnson ]
This device then solves the entire problem.
A circuit breaker is similar, but is resettable.
Can the fuse protect the electronic devices from lightning instead of a surge protector.
Once the voltage goes over 0.0650 volts, then this fact can be used to amplify the difference, and turn the circuit breaker off , furthur down the line. Essentially that is what a RCD/GFCI does, it compares the incoming current, to the outgoing current, and if the difference between the two currents is over 5mA, then it trips the circuit breaker.
It also is a device that limits the change in current flow.
In schematic diagrams this is the symbol for a fuse:
“ A surge suppressor is the one which is connected at the input supply so that when there is a sudden change voltage it bypasses thereby protecting the (circuit) and electronic components”
And this is the problem alone. Is the power supply in the equipmemt designed with a lightning strike in mind? Some yes, others, no.
One is “what exactly is in a ‘surge protector’ ? ”
So, it’s possible that these devices from Trip Lite have addition suppression devices, these ones seem to be sturdy.
Lightning arrestor is a spark-gap device, and can be installed anywhere. What is important, is that the wire is thick enough to withstand the lightning bolt and conduct the energy away from the building.
This is the picture of an electronic coil of wire wound around a core of magnetic material.
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This is where the MOV conducts again, and dissipated the energy.