Long extension cords: increased risk from lightning strikes?

[80251]

If you use a long heavy gauge extension cord to run your computer or stereo equipment does that increase the risk of damage from lightning strikes through induction?

 

[MarsM4N]

Only if you run the cable outside. If the lightning hits your house & you got no earthwire on your roof, then your PC is the last to worry about.

 

[joemama]

Unless you're hanging the cords outside of the house and high in the air

 

[80251]

I had thought a lightning strike, even if it doesn't hit your domicile, produces an EMP burst. I had also thought long runs of wire can act as antennae making them more subject to the effects of the lightning EMP burst.
I once had a fast moving thunderstorm move through my city. A lightning strike that didn't hit my house but struck nearby brought my computer down and even messed up my Asus Pg279 or the videocard because I couldn't get any video output through DP anymore. I had to hook up my LCD via HDMI to get any video output. Once I did that though the DP magically came back to life and I was able to switch back to using DP.

 

[ThrashZone]

Hi,
As said not unless it's running outside to inside

Heavy gauge extension cord the gauge wire it has should not be larger than what's used in the wall outlet
So if the wall outlet has 16 gauge wire you wouldn't want to use a 12 gauge extension cord.
Then define what exactly is "long" if you need 25 foot don't use a 100 foot cord.

 

[Bill_Bright]

Assuming the gauge is large enough (the smaller the gauge number the bigger the wire), and the cord and connectors are in good repair, and (as mentioned), all is indoors, the bigger risk is tripping over the cord, insect damage, and teething puppy dawgs!

I had also thought long runs of wire can act as antennae making them more subject to the effects of the lightning EMP burst.

Not typically with AC power cords. Data cables, maybe - if not shielded.

***

Me thinks someone is caffeine deprived this morning:

Heavy gauge extension cord the gauge wire it has should not be larger than what's used in the wall outlet

Ummm, sorry but this is totally backwards! You can always go larger. What you should not do is go smaller (except for short distances and when powering low wattage devices).

So if the wall outlet has 16 gauge wire you wouldn't want to use a 12 gauge extension cord.

Yeah, sorry but again totally inaccurate. If the wall has 16 gauge, you DO want to use 12, or even 10 gauge for a long cord powering hungry electronics.

Again, the smaller the gauge number the bigger the wire.

And just for the record, in the US, 14-gauge facility wiring is considered small these days and should only be used on 15-amp circuits. In new construction, you typically see 12-gauge and most circuits are at least 20-amp. In fact, in some areas, using anything smaller than 12-gauge violates code.

 

[robot zombie]

Honestly, a lot of US extension cords should be thicker, or rated lower. They can get pretty hot below their max current ratings.

 

[Bill_Bright]

Honestly, a lot of US extension cords should be thicker, or rated lower. They can get pretty hot below their max current ratings.

This is why Christmas time is often a firefighter's nightmare time - too many people overload inadequate extension cords (and wall outlets) with too many strings of Christmas lights.

 

[80251]

Just like with shotguns, the lower the gauge the bigger the projectile and the cable.

The extension cord in question is roughly 18' long.

 

[Bill_Bright]

The extension cord in question is roughly 18' long.

That's only half the unknown. The other half is the load.

 

[Shrek]

If you use a long heavy gauge extension cord to run your computer or stereo equipment does that increase the risk of damage from lightning strikes through induction?

Well, neutral, live and ground voltages will be moved an equal amount, so the difference should remain the same (we are not talking a direct hit here).

 

[caroline!]

Nothing will happen but it's always better to run a new wall socket -or move the computer- than using really long extension cords, power strips, multiplugs, etc.

 

[80251]

That's only half the unknown. The other half is the load.

The problem is I have everything (monitor, receiver, computer) on two 110VAC US outlets located within 4' of one another. I was thinking with an extension cord I could at least get the receiver and/or the computer on an outlet located farther away.

Anyone who doubts the fact a longer run of cable results in increased voltage/current due to inductance by lightning strikes (which need not be direct) needs to check their physics:

https://electronics.stackexchange.c...tage-inductance-lightning-in-a-length-of-wire

in particular:

Given the inductance for a given length of wire, the induced voltage along the length is given by:

v=L di/dt

So the greater the rate of change in current, the greater the induced voltage.
Hence the longer the wires. The greater is the surge voltage.

 

[TheUn4seen]

Not at all, any extension cord will be far too short to be electromagnetically coupled with a lightning strike so induction will not occur in any significant way - it will, of course, occur, but will be far within acceptable threshold of any modern electronics. External power infrastructure, however, is, hence surge protection on the input to the house is very important, especially in rural areas with cables on poles.

Anecdotally, when a lightning stroke a tree just outside my window only damage occurred when the tree literally exploded due to it's liquids being boiled in milliseconds - that's why you should never hide close to a tree during storms - and pieces of it broke glass in my window. No electronics were harmed that day.

 

[80251]

Not at all, any extension cord will be far too short to be electromagnetically coupled with a lightning strike so induction will not occur in any significant way. External power infrastructure, however, is, hence surge protection on the input to the house is very important, especially in rural areas with cables on poles.

Anecdotally, when a lightning stroke a tree just outside my window only damage occurred when the tree literally exploded due to it's liquids being boiled in milliseconds - that's why you should never hide close to a tree during storms - and pieces of it broke glass in my window. No electronics were harmed that day.

Have you ever studied the propagation of electromagnetic waves or induction? Maybe you should start by reading the article I cited.

 

[TheUn4seen]

Have you ever studied the propagation of electromagnetic waves or induction? Maybe you should start by reading the article I cited.

You know this article talks about surge protection on the input to the equipment (a house in case of residential areas) and microsecond pulses in the order of hundreds of volts? That's insignificant. A one cent MOV will handle that easily. If you worry, get a surge protector on the end of the cable, any EM pulse strong enough to cause problems will fry your electronics directly, inducing current in PCB traces. Of course, you would need a nuclear explosion nearby to create such a pulse, at which point induction is the least of your problems, but who knows in this crazy world we live in.

 

[Shrek]

Anyone who doubts the fact a longer run of cable results in increased voltage/current due to inductance by lightning strikes (which need not be direct) needs to check their physics:

https://electronics.stackexchange.c...tage-inductance-lightning-in-a-length-of-wire

in particular:

Given the inductance for a given length of wire, the induced voltage along the length is given by:

v=L di/dt

So the greater the rate of change in current, the greater the induced voltage.
Hence the longer the wires. The greater is the surge voltage.

Absolutely, that is why I wrote "neutral, live and ground voltages will be moved an equal amount, so the difference should remain the same"

It is an interesting problem and relates to the idea that one should connect to ground at one place only to avoid ground loops, where the induced voltage would result in an induced current.
Ground loop (electricity) - Wikipedia

 

[1freedude]

Induction and inductance are different

 

[ThrashZone]

The problem is I have everything (monitor, receiver, computer) on two 110VAC US outlets located within 4' of one another. I was thinking with an extension cord I could at least get the receiver and/or the computer on an outlet located farther away.

Hi,
I'm not getting into the lightening deal besides get a battery back up system

As far as these three plugs and extension cord goes
If all three plugs/ wall outlets are on the same circuit "refer to your main breaker box" you're spinning your wheels because it makes no difference besides which plug is first from the home run which comes from the breaker box usually to a light switch... and branches off from there to room plugs.

If this third plug is on a totally different circuit it's worth shifting the receiver and monitor to it
Leave the computer closest to desk not on a extension cord.

 

[looniam]

The problem is I have everything (monitor, receiver, computer) on two 110VAC US outlets located within 4' of one another. I was thinking with an extension cord I could at least get the receiver and/or the computer on an outlet located farther away.

Anyone who doubts the fact a longer run of cable results in increased voltage/current due to inductance by lightning strikes (which need not be direct) needs to check their physics:

https://electronics.stackexchange.c...tage-inductance-lightning-in-a-length-of-wire

in particular:

Given the inductance for a given length of wire, the induced voltage along the length is given by:

v=L di/dt

So the greater the rate of change in current, the greater the induced voltage.
Hence the longer the wires. The greater is the surge voltage.

i think you're making a boo boo, but i only just glanced at that and it talks about the ground from your service panel - or for the whole "house" - that is a different can of worms than a simple extention cord. if your ground is too close to your neighbors, you're gonna have issues, whereas extention cards with much lighter loads will not be affected.

i'm sure an actual licensed electrician can explain it better, sorry i can't since i only play one on TV.

 

[80251]

You know this article talks about surge protection on the input to the equipment (a house in case of residential areas) and microsecond pulses in the order of hundreds of volts? That's insignificant. A one cent MOV will handle that easily. If you worry, get a surge protector on the end of the cable, any EM pulse strong enough to cause problems will fry your electronics directly, inducing current in PCB traces. Of course, you would need a nuclear explosion nearby to create such a pulse, at which point induction is the least of your problems, but who knows in this crazy world we live in.

Yes a lightning strike is analogous to an impulse. The fact that it's of short duration only means the change in current is faster which means even MORE surge voltage is induced.

 

[Bill_Bright]

Anyone who doubts the fact a longer run of cable results in increased voltage/current due to inductance by lightning strikes (which need not be direct) needs to check their physics:

What? It is you who needs to get yourself educated here. First, this cable is running inside the house. Longer runs increase resistance. Inductance is not a factor in this scenario unless running a bunch of parallel extension cords and there is no mention of that. If what you said was even remotely true, then every wire inside nearly every wall in every house would be susceptible to lightning strikes and that is not happening.

Now if by a slim chance the house takes a directly lightning hit - then all bets are off as Mother Nature is going to do whatever she wants.

As I said above, the bigger issue (beside physical damage or overloading the extension cord) is tripping over it.

 

[bonehead123]

And just for the record, in the US, 14-gauge facility wiring is considered small these days and should only be used on 15-amp circuits. In new construction, you typically see 12-gauge and most circuits are at least 20-amp. In fact, in some areas, using anything smaller than 12-gauge violates code.

^^THIS^^

I have lived lots of places in the US over the years, and have yet to encounter any place that 12GA wire was not the REQUIRED minimum by the building codes for indoor circuits to normal/standard 110-115 volt, 15-20 amp outlets, switches etc... UNLESS the end point is moar than 100ft away from the start point (breaker box), in which case the codes usually require stepping it up 1 size to 10GA. And as already stated, the load also has to be considered. This is not only for safety, but also to prevent voltage dropoff, which will occur rapidly after 100ft.

Higher voltage circuits, like 220 volt/30 amp for your water heaters and electric clothes dryers (and 50 amp for electric ranges) normally require 10GA, 3-conductor wiring to handle the increased loads these appliances pull from the breaker box.

Low voltage stuff like doorbells, pathway lights, thermostats usually are made with step down transformers (to go from regular 110v to 24, 12 or even 6v) and can be as small as 16 or 18GA...

If you don't understand this type of stuff, just call a local electrician and ask, most of them are glad to answer your questions.....just don't rely on the electrician-wannabe's at Lowes or Home depot though, as most (but not all) of them are generally clueless

 

[Count von Schwalbe]

^^THIS^^

I have lived lots of places in the US over the years, and have yet to encounter any place that 12GA wire was not the REQUIRED minimum by the building codes for indoor circuits to normal/standard 110-115 volt, 15-20 amp outlets, switches etc... UNLESS the end point is moar than 100ft away from the start point (breaker box), in which case the codes usually require stepping it up 1 size to 10GA. And as already stated, the load also has to be considered. This is not only for safety, but also to prevent voltage dropoff, which will occur rapidly after 100ft.

Higher voltage circuits, like 220 volt/30 amp for your water heaters and electric clothes dryers (and 50 amp for electric ranges) normally require 10GA, 3-conductor wiring to handle the increased loads these appliances pull from the breaker box.

Where I live, 14 ga is acceptable for up to 15A. Also, 3-conductor is only required if the appliance needs a neutral.

@80251 if you live in a facility constructed to US detached residential electrical code (or similar), AKA no conduit for your wiring, an extension cord will not change anything, as it is just as vulnerable as the house wiring. If you do have conduit for your wiring, an extension cord will slightly increase the inducted voltage in the event of a lightning strike. However, I doubt that the effect would be remotely significant if your cord is under 100ft. A simple surge protector will negate this - they are not expensive.

 

[robot zombie]

Also, 3-conductor is only required if the appliance needs a neutral.

In the case of ALL of those two-phase appliances the code has long since changed to require 4-conductors. Only existing homes will have the 3-conductor outlets. It was once considered acceptable to wire the ground to the neutral in those appliances. That hasn't been the case for some time now though, as there are instances when this results in the enclosure becoming energized at 120v. Chaining ground to neutral, the return path carrying 120v back in most cases with these appliaces, can lead to that if there is ever a problem with the connection of the neutral on its way back to the sub panel. There's nowhere for it to go but through you, when you say, open the hatch. By isolating the enclosure from the return path and linking it straight to the grounding points on the panel, you remove this risk.

Any new appliance like this now will have a jumper that allows you to bridge them for the older 3-wire, but that way of doing things is earmarked for death as those outlets slowly disappear. But it also means that less people get electrocuted. I never understood why that was ever considered acceptable tbh.

250.140 Frames of Ranges and Clothes Dryers. Frames
of electric ranges, wall-mounted ovens, counter-mounted
cooking units, clothes dryers, and outlet or junction boxes
that are part of the circuit for these appliances shall be
connected to the equipment grounding conductor in the
manner specified by 250.134 or 250.138.

Exception: For existing branch-circuit installations only
where an equipment grounding conductor is not present in
the outlet or junction box, the frames of electric ranges,
wall-mounted ovens, counter-mounted cooking units,
clothes dryers, and outlet or junction boxes that are part of
the circuit for these appliances shall be permitted to be
connected to the grounded circuit conductor if all the following
conditions are met.

(1) The supply circuit is 120/240-volt, single-phase, 3-wire;
or 208Y/120-volt derived from a 3-phase, 4-wire, wyeconnected
system.

(2) The grounded conductor is not smaller than 10 AWG
copper or 8 AWG aluminum.

(3) The grounded conductor is insulated, or the grounded
conductor is uninsulated and part of a Type SE serviceentrance
cable and the branch circuit originates at the
service equipment.

(4) Grounding contacts of receptacles furnished as part of
the equipment are bonded to the equipment.

Basically what this means is that you now need the ground for all of those, an actual GROUNDING conductor... as in straight to ground, not the GROUNDED neutral. With 2-phase 240v to your range, dryer, etc, that means 4 conductors, pretty much without exception.

In a more general sense, ground should only be linked to neutral at the main service panel. That is another exception where you could probably still use a 3-conductor - if the outlet is wired straight to the main panel, you might be getting away with it, though I'm not digging for that one. The majority of homes in the US have them coming from a branch off of the sub panel, where it's not even on the table in any sense. Not in the US, anyway.

I would also add, how may of those appliances DON'T require a neutral to operate these days? Most of them have other circuitry that requires only 1 phase. All of that stuff in the panels for those appliances is 120v, not 240. Buttons, screens, control hardware, that kind of stuff. Not so much of the clicky relays and potentiometers.