News You Can Use: What Happens When a 63 Amp, 36000 Volt Fuse Blows?

Last year, a solar power farm in the United Kingdom had a really bad day and blew one of the main fuses on its three-phase AC output feed.  (If you work it out, this phase had a maximum power of 2.25 megawatts.)  An engineer sent the blown fuse to Big Clive, who proceeds in the following video to find out what’s inside with the cheap-o X-ray device, how it works, and what the aftermath of  a blown fuse event looks like.  Cameo appearance by an ever-helpful cat.

The fuse is rated to break a short-circuit current of 40,000 amperes.  The 36 kV rating is between phases, with 20 kV above ground.

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Author: John Walker

Founder of Ratburger.org, Autodesk, Inc., and Marinchip Systems. Author of The Hacker's Diet. Creator of www.fourmilab.ch.

13 thoughts on “News You Can Use: What Happens When a 63 Amp, 36000 Volt Fuse Blows?”

1. What is a normal home fuse? My breakers are 15 Amps and 20 Amps.

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2. 10 Cents:
What is a normal home fuse? My breakers are 15 Amps and 20 Amps.

It depends upon the application of the circuit.  Regular lighting and utility circuits are usually 10 or 16 amp (note that our nominal voltage is 230 volts, so you get twice the power per ampere as on 110/120 volt power in the U.S. and Japan).  My home power panel also has 20 amp fuses on heavy-duty circuits such as oven, clothes dryer, and (retired) furnace blower.  The main before-meter fuses are 25 amp, 380 volt.

But this is somewhat confusing because in Switzerland and much of Europe, heavy power circuits such as ovens, clothes dryers, etc. tend to be 380 volt three phase, so a lower amperage fuse gives you substantially more power than a 230 volt single phase pair.

Here is the main Fourmilab power panel, where the feed to the compound from our dedicated substation arrives.

Those 400 amp fuses are not in Big Clive territory, but somewhat bigger than a beer can.  It is possible to blow them; I’ve blown one.  That was an exciting day.

Inside the substation there are 8 ampere fuses on each of the 16,000 volt phases.

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3. Obviously the very thin wire threaded through the innermost ceramic form was connected to the other end of the fuse. He didn’t examine that part on the video, but that was what held the plunger in.

And for the guidance of fellow Ratburgers, I offer an image of various types of fuses and their current capacity.

Take note of the 350 Amp with the audiovisual auto-alert !

Also note that the 2000 amp (slow-blow) is Metric, but have no fear, there are equivalent available types, labeled 7/16, that can be used in the U.S.A..

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4. Sorry John, You seemed to like my comment before I explained the U.S.A replacement for the “metric” fuse.

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5. 10 Cents:
What is a normal home fuse? My breakers are 15 Amps and 20 Amps.

If your power is 120/240 volts, then typically most of your circuit breakers will be of that variety.

The 15 Amp are for general purpose low power consumption, lighting and outlets in the living area of the home. The 20 Amp breakers would be for appliances that draw more power, typically kitchen areas or an electric washing machine. A “gas” dryer would be on either a dedicated 20 Amp or 15 Amp circuit. An electric dryer would be connected to a 30 Amp dual, or 240 volt, circuit breaker. An electric stove would be connected to a 40 Amp dual, or 240 volt, circuit breaker. Electric water heaters are typically connected to a 30 Amp dual, or 240 volt, circuit breaker, but sometimes smaller water heaters can be connected to a 20 Amp dual, or 240 volt, circuit breaker.

The main power disconnect is typically a dual 100 Amp circuit breaker, some homes have 200 Amp, (mine does). Older homes may still have a 60 Amp main breaker. It is very rare to find homes with less power that that.

Back in May of 1970, I rewired my parents home. It used a single 15 Amp fuse for the whole house! The wiring was knob and tube type and it was only 120 volts. When I was done, it had a new 100 Amp 240 volt service and every room had it’s own circuit breaker, except the kitchen, there I installed two 20 Amp circuit breakers for the outlets and another 15 Amp for the lighting.

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6. 10 Cents:
What is a normal home fuse? My breakers are 15 Amps and 20 Amps.

It depends upon the application of the circuit.  Regular lighting and utility circuits are usually 10 or 16 amp (note that our nominal voltage is 230 volts, so you get twice the power per ampere as on 110/120 volt power in the U.S. and Japan).  My home power panel also has 20 amp fuses on heavy-duty circuits such as oven, clothes dryer, and (retired) furnace blower.  The main before-meter fuses are 25 amp, 380 volt.

But this is somewhat confusing because in Switzerland and much of Europe, heavy power circuits such as ovens, clothes dryers, etc. tend to be 380 volt three phase, so a lower amperage fuse gives you substantially more power than a 230 volt single phase pair.

Here is the main Fourmilab power panel, where the feed to the compound from our dedicated substation arrives.

Those 400 amp fuses are not in Big Clive territory, but somewhat bigger than a beer can.  It is possible to blow them; I’ve blown one.  That was an exciting day.

Inside the substation there are 8 ampere fuses on each of the 16,000 volt phases.

I would have thought The  Fourmilab was Top Secret? Pictures on the net?

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7. That thing the guy in the video is calling “an X-ray device” is what I call “a fine optical alignment tool.” It is only used in moments of extreme frustration in the lab.

me: Dave, hand me the Fine Optical Alignment Tool.
Dave: No, not the FOAT!
me: Yes, it’s come to this.

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8. drlorentz:
That thing the guy in the video is calling “an X-ray device” is what I call “a fine optical alignment tool.” It is only used in moments of extreme frustration in the lab.

me: Dave, hand me the Fine Optical Alignment Tool.
Dave: No, not the FOAT!
me: Yes, it’s come to this.

A: Hand be a socket.

B: What size?

A: It doesn’t matter. I need to use it as a Fine Optical Adjustment Tool.

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9. I’m a bit jealous that you have your own substation.

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10. Phil Turmel:
I’m a bit jealous that you have your own substation.

Here’s the “Fourmilab welcome mat”: the “Danger de mort” sign outside the substation.  Yes, that’s Donald E. Knuth with me when he visited here in November 2005.

Here is the Big Switch.  The little fuses at the bottom right are for the meter.

Yes, those copper bus bars are live.  They’re flat to minimise losses due to skin effect, which at these power levels is significant even at 50 Hz.

This is the serial number and specification panel on the main transformer.

You always want to have some spare fuses.  The ones are the left are for the 16 kV inputs, while those on the right are for the 380 V outputs.

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11. John Walker:
They’re flat to minimise losses due to skin effect, which at these power levels is significant even at 50 Hz.

Shouldn’t that really be called the core effect?  See what you can do.

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