Surge Protection - at the Wall Charger & the Tesla Itself?

[ACRei]

This is an odd question that came to mind from an observation this evening:

Someone turned on a dryer this evening and I noticed a subtle dimming on a ceiling light.

I assumed it was a fluctuation in power from the dryer turning on, and, after half a second, everything was fine.

If something similar happened while my Model 3 was charging on the Gen 3 Wall Charger, would it cause any harm? I’d assume both the wall charger and the Tesla are robust enough to avoid any harm, since the former is properly grounded/installed, and the Tesla can resist most surges on its own. I just wanted to verify.

Overthinking it further, I imagined if the charger was limited to 32A and there was a slight fluctuation and the Amperage dropped for a few moments and suddenly came back up, is it safe to say the Charger would suppress any surge attempting to go above 32A? Or would it be the Tesla suppressing any surge? Or is it a combo of both?

Thanks for your patience in reading all that, and also for any assistance you can give me in understanding this.

 

[Tronguy]

Um. Two things, or at least two things.

First, city power is absolutely well known to have voltage dips, rises, overvoltages, and all that jazz. Lighting strikes on the telephone poles outside one’s house is just the worst of those, big enough to blow holes in equipment. But there’s lots of arcs and sparks coming down those wires from contactors opening and closing, inductive kicks from big electric motors stopping, and the occasional errant soccer ball hitting the power lines so they brush up against each other, releasing the sparks (actually saw that once). 300 or 400 volt bangos in the millisecond to tens of microsecond ranges are pretty much normal.

Now for the weird statement. People with Degrees hath been sent out from their Ivory Towers and their commercial equivalents to attach monitoring equipment to capture huge amounts of characterization data; from that data, Standards For Equipment Connected to City Power Hath Been Written and Enforced. The general feeling being that burning buildings and everything to the ground should be considered a Bad Thing and Not Good For Society. Yes, the Gummints of the world are, at least notionally, behind this, not to mention power companies, who would like not to have events discouraging their product.

There exist standards up the wazoo for equipment hooked to power lines. All those barely discernible letters on your wall warts side: UL, CSA, EU, FDE, etc, etc all pertain to standards and tests that are run to make sure that things operate in the presence of all the garbage and hopefully don’t burst into flames when nearly hit by actual lightning, which is Other.

Things that do burst into flames usually turn out to be cheap Amazon knockoffs, where forging all those credentials in the interests of profits is a way of life. You won’t find the deathly crap at big box stores because they a) can be found by people with lawsuits and b) the stores employ lawyers who can usually explain to the dumbest of pointy-haired bosses the errors of their ways. And that said bosses would be personally liable.

So, generally, given that we’re talking vendors of power equipment here, I really wouldn’t expect that a random power surge, or even a honking big one, would damage a mobile connector, wall connector, or the car for that matter.

What you likely noticed was a big AC motor starting, and not all that well at that. When inductive loads like motors start they typically draw 2x or 3x their normal current draw, then drop the load current as the motor spins up. This is why nearly every breaker and a heck of a lot of fuses have slow-blow characteristics, so they don’t nuisance blow on startups like that. Normally such events are barely noticeable, unless one is paying close attention. The sudden current draw causes the house voltage to droop.

Dips won’t bother a Tesla, it’s battery powered. And the wall or mobile connector probably would need a heck of a dip (like the lights going out) before anything happened. And anything happening would generally be a restart, not something breaking.

But if this is something new and getting worse.. could be a motor starter capacitor going bad. It’s like this: with a 3-phase motor, it’s easy enough to create a rotating magnetic field that drags the rotor around in the right direction. But most houses in the US and Canada are single phase, either 120 or 240 VAC. As a result , it’s pretty easy to build a motor that if it gets power applied Just Wrong it’ll stall and draw enough current to either melt its own wires or the ones in the walls. So, such motors often have a small, secondary winding in there at an odd angle, powered through a mid sized capacitor to give it a phase angle that guarantees the motor starts turning in the right direction. These Starter Capacitors are pretty reliable, but are known to die or become less effective with age. So, you might want to get that checked out, before the motor immolates itself.

Other possibilities for your light dimming enjoyment might be loose connections, in the breaker panel or further north in the utility somewhere. It’s happened.

Finally: most households don’t have to sweat lightning. There’s Reasons why that top wire on power poles with wires heading straight into ground exist. But there are exceptional cases. The one I’ve heard about is the isolated farmer’s house on a small hill with a power line stretching across the quarter mile of fields to get to house. After the nth time all the electronics in the house got fried (I did say lightning was, “Other”), the guy hired an electrician. Who put a heavy-duty surge protector on the side of the farmer’s house, whose first stage was a bunch of spark gaps which would arc across at 3,000 volts or so, followed by even more chokes and MOVs after that. Expensive, but the farmer’s TV set stopped needing repetitive replacement.

Fun.

 

[NeverGoingBack]

Perhaps the most entertaining and informative post I’ve read on here. Thanks @Tronguy !

 

[turns2stone]

The right way is to install a surge protector at the panel: Eaton Whole House Surge Protector CHSPT2ULTRA-1 - The Home Depot

The Tesla can handle voltage drops just fine.

 

[jjrandorin]

Perhaps the most entertaining and informative post I’ve read on here. Thanks @Tronguy !

I learn something every time @Tronguy responds to something. Check out some of their other posts, they are a great read.

 

[Tronguy]

The right way is to install a surge protector at the panel: Eaton Whole House Surge Protector CHSPT2ULTRA-1 - The Home Depot

The Tesla can handle voltage drops just fine.

Heh, heh, heh.

As it happens I've spent 'way too much time messing about with Real Life lightning surges, both in the field and in the lab, Combination Waveform Generators and All. Mind you, this is telco stuff, not city power, but you'll have to take my word for it: It's Strongly Related.

That nifty little thing (and it is little) that Eaton is hawking gets wired up in parallel with city power to ground. It's no better or worse than the surge protector one buys for one's PC and such.. and, possibly, since it appears to be a parallel box, probably worse.
Let's see if I can do a little graphic. LTSpice, Away!

So, left side is outside ye house; right side, inside ye house. One gets a lightning strike (See: U1) and, in this particular example, V1 goes from 120 VAC to Something Enormous. Something Enormous is on its way to blow up whatever is inside the "Load on 120VAC" and, the first thing it runs into is U2, a varistor. Varistors are generally of the flavor of that, below some threshold, they don't conduct; above some threshold, they act pretty close (but not quite) to a short circuit. And they do that... quickly.

Now, see that "Low Pass Filter"? Lightning strikes have rise times in the single to tens of microseconds; or, looking at it another way, frequency content from 50 kHz up to roughly 1 MHz. That low pass filter has enormous impedance at those frequencies; darn near zero at 60 Hz. So, between U2 and that LPF, we get a voltage divider of ratio Z_of_U2/(Z_of_U2 + Z_of_LPF), which is tiny, and results in maybe 100 V on top of the 120 VAC being passed onto Ye Load.

What is being described above is pretty much what one finds in a good grade surge protector that one would put around one's PC. Ye typical surge protector comes with itty bitty filters on Hot, Neutral, and Ground (all three!), MOVs (Metal Oxide Varistors, and TVS Diodes, another specie of the same thing, but faster reacting) from hot to neutral, hot to ground, and neutral to ground. In general, they do a pretty decent job.

These varistors, though. If one looks in Power Company Switching Yards, those varistors come in hockey-puck sizes, get stacked, and can absorb megajoules of energy. The ones that one finds in a consumer grade surge protector can handle something south of ten joules or so, which, for the application, is fine.

But, there's a trick: MOVs have a finite life time. Surge them right at the specified limit (say, a 10 J surge on a 10 J device), and one might get a couple dozen hits before the MOV fails, either open (in which case it doesn't do much for one) or short, in which case it pops a breaker. The better grade of surge protectors have a little light which indicates Death of MOV, in which case it's time to replace the surge protector. Surge the same thing at 1 J and one might get a couple thousand or even a hundred thousand hits before it gives up the ghost.

Now, that farmer's house of which I spoke? In front of those filters, that place had, on each incoming wire to the local copper ground stake two contacts, separated precisely by a certain amount of Air. Get more than a couple thousand volts, Ye Air Breaks Down and one gets an almighty Zap! that the contacts are built for. This limits the voltages going into the filters and Saves The House and MOVs.

Now, let's go back to that itty bitty Eaton box. It's sooooo cute. It very definitely doesn't have the house power wires going through it. I absolutely guarantee you, it's got those MOVs in there, wired between the two hots, one hot to ground/neutral, and the other hot to ground/neutral. And a detector to tell one when the MOVs have died.

When Ye Lightning Strikes, the MOVs will conduct. But, as I said before, MOVs aren't perfect, they don't go to Dead Short, just something low, in the vicinity of a couple of ohms to maybe ten ohms or so. The impedance they're working against? It ain't the filter, there isn't one. It's the impedance of the Power Company. So at 60 Hz, the power company impedance is in the small milliohms, mainly the wire going back to the local transformer. At 50 kHz to 1 Mhz... Who knows? But it's likely Not Big. Which means... Little bitty surges this thing might help. Great Big Whoppers, it won't do a thing for one before the MOV disintegrates and gets scattered across the metaphorical landscape.

Advantage of the Eaton box: It's cheap and easy to install. Disadvantage: It's a blame Fig Leaf. One would be better off, at least for one's PCs and TV sets, to get a Home Depot surge protector. Marginal improvement.. maybe.

Ya Get What Ya Pay For. What else is new?

 

[turns2stone]

Advantage of the Eaton box: It's cheap and easy to install. Disadvantage: It's a blame Fig Leaf. One would be better off, at least for one's PCs and TV sets, to get a Home Depot surge protector. Marginal improvement.. maybe.

Ya Get What Ya Pay For. What else is new?

When you say "Home Depot surge protector", you mean the Eaton box I linked? Because most people who pick up a $15 8-outlet 'surge protector' at Home Depot are actually buying taps, which do nothing but add more outlets to your socket. False sense of security, in my experience.

 

[Tronguy]

When you say "Home Depot surge protector", you mean the Eaton box I linked? Because most people who pick up a $15 8-outlet 'surge protector' at Home Depot are actually buying taps, which do nothing but add more outlets to your socket. False sense of security, in my experience.

Just meant the standard type that one plugs into a 120 VAC wall socket. If it says, "surge protector", it has to have something in there, and not just raw wire and taps.

 

[turns2stone]

Just meant the standard type that one plugs into a 120 VAC wall socket. If it says, "surge protector", it has to have something in there, and not just raw wire and taps.

Right. Some little baby MOVs in most of those.

 

[ACRei]

Um. Two things, or at least two things.

First, city power is absolutely well known to have voltage dips, rises, overvoltages, and all that jazz. Lighting strikes on the telephone poles outside one’s house is just the worst of those, big enough to blow holes in equipment. But there’s lots of arcs and sparks coming down those wires from contactors opening and closing, inductive kicks from big electric motors stopping, and the occasional errant soccer ball hitting the power lines so they brush up against each other, releasing the sparks (actually saw that once). 300 or 400 volt bangos in the millisecond to tens of microsecond ranges are pretty much normal.

Now for the weird statement. People with Degrees hath been sent out from their Ivory Towers and their commercial equivalents to attach monitoring equipment to capture huge amounts of characterization data; from that data, Standards For Equipment Connected to City Power Hath Been Written and Enforced. The general feeling being that burning buildings and everything to the ground should be considered a Bad Thing and Not Good For Society. Yes, the Gummints of the world are, at least notionally, behind this, not to mention power companies, who would like not to have events discouraging their product.

There exist standards up the wazoo for equipment hooked to power lines. All those barely discernible letters on your wall warts side: UL, CSA, EU, FDE, etc, etc all pertain to standards and tests that are run to make sure that things operate in the presence of all the garbage and hopefully don’t burst into flames when nearly hit by actual lightning, which is Other.

Things that do burst into flames usually turn out to be cheap Amazon knockoffs, where forging all those credentials in the interests of profits is a way of life. You won’t find the deathly crap at big box stores because they a) can be found by people with lawsuits and b) the stores employ lawyers who can usually explain to the dumbest of pointy-haired bosses the errors of their ways. And that said bosses would be personally liable.

So, generally, given that we’re talking vendors of power equipment here, I really wouldn’t expect that a random power surge, or even a honking big one, would damage a mobile connector, wall connector, or the car for that matter.

What you likely noticed was a big AC motor starting, and not all that well at that. When inductive loads like motors start they typically draw 2x or 3x their normal current draw, then drop the load current as the motor spins up. This is why nearly every breaker and a heck of a lot of fuses have slow-blow characteristics, so they don’t nuisance blow on startups like that. Normally such events are barely noticeable, unless one is paying close attention. The sudden current draw causes the house voltage to droop.

Dips won’t bother a Tesla, it’s battery powered. And the wall or mobile connector probably would need a heck of a dip (like the lights going out) before anything happened. And anything happening would generally be a restart, not something breaking.

But if this is something new and getting worse.. could be a motor starter capacitor going bad. It’s like this: with a 3-phase motor, it’s easy enough to create a rotating magnetic field that drags the rotor around in the right direction. But most houses in the US and Canada are single phase, either 120 or 240 VAC. As a result , it’s pretty easy to build a motor that if it gets power applied Just Wrong it’ll stall and draw enough current to either melt its own wires or the ones in the walls. So, such motors often have a small, secondary winding in there at an odd angle, powered through a mid sized capacitor to give it a phase angle that guarantees the motor starts turning in the right direction. These Starter Capacitors are pretty reliable, but are known to die or become less effective with age. So, you might want to get that checked out, before the motor immolates itself.

Other possibilities for your light dimming enjoyment might be loose connections, in the breaker panel or further north in the utility somewhere. It’s happened.

Finally: most households don’t have to sweat lightning. There’s Reasons why that top wire on power poles with wires heading straight into ground exist. But there are exceptional cases. The one I’ve heard about is the isolated farmer’s house on a small hill with a power line stretching across the quarter mile of fields to get to house. After the nth time all the electronics in the house got fried (I did say lightning was, “Other”), the guy hired an electrician. Who put a heavy-duty surge protector on the side of the farmer’s house, whose first stage was a bunch of spark gaps which would arc across at 3,000 volts or so, followed by even more chokes and MOVs after that. Expensive, but the farmer’s TV set stopped needing repetitive replacement.

Fun.

Ty, @Tronguy . That was by far the most informative post I've read on this forum. And thank you for the answer(s) ; very much appreciated.

 

[ay221]

Even with all that, if there is a bad lighting storm, I don't think I could leave my Tesla plugged in. Would probably be an overreaction?

 

[Tronguy]

Even with all that, if there is a bad lighting storm, I don't think I could leave my Tesla plugged in. Would probably be an overreaction?

Risk vs. reward. Your TV set and/or computer is probably about the same or worse than a Tesla in terms of being able to withstand Ye Olde Lightning Surge. (More on that in a bit). Not to mention other electronics that most people don't bother to use surge protectors with: Clock radios, stereo systems, and modern clothes washers, clothes driers, microwaves, stoves, and all that with nifty-looking luminescent displays. A standard incandescent bulb is pretty resistant to garden variety surges; but all those compact florescents and LED bulbs have serious electronics in them, not to mention dimmer switches. Actually, that last is even more resistant to surges than most electronics; it's hard to mess with an SCR, they electrically break down on an overvoltage (they're supposed to) and recover pretty easily. In fact, that's more-or-less how they work.

So, if none of that has been going blooey (technical term) on a regular basis around your domicile over the time you've lived there then it's likely that a Tesla isn't going to change the equation. As I've said before, there's all those nifty safety designations on a Wall Connector and Mobile Connector, which means that Tesla has Tested These Things against Ye Standards (just like the clock radio people did) and everything survived.

There's actually several things going for people living in homes. First off, in most residential districts of which I've wandered through, on the Very Top of the telephone poles, there's a single wire going from pole to pole to pole. If one looks carefully, either on every pole or once every N poles there's a wire (Let's call it Wire G for the moment) making solid contact with that top-most wire; that G wire is physically attached to the telephone pole and goes all the way to the base of the pole, where it meets up with a copper ground stake, plunged deeply into the soil. The general idea is that a couple million volts and a couple thousand amps from the sky hit the path of least resistance, which is that top wire and the multiplicity of G wires, and all that energy heads straight for Ground. And not, exactly, heading down the wires between the pole and one's house.

The "not exactly" bit has to do with magnetic fields from the jolt. As you all may remember from Kindergarten or First Grade, there's a science experiment for the kiddies where a battery-powered wire is put straight through a piece of paper; then, iron filings are scattered across the surface of the paper and, ta-da! little circular rings of iron filings form that go around the wire in the paper. They are, literally, lining up with the magnetic field lines that are caused by the current flowing through the wire. The iron clumps most near the wire, less so as one goes away from the wire, thank you, Dr. Maxwell.

With a lightning strike current going through the G wires (or the iron members of a skyscraper) on their way to ground, those magnetic fields don't just replicate the Kindergarten experiment; they MOVE. The current starts at zero, goes up to something gigantic, then back to zero, all the space of a hundred microseconds or so, and the magnetic fields move in sync with the current. Now, those moving magnetic fields, first expanding, then contracting, will cross through all the other wires in the vicinity. A moving magnetic field crossing through a wire will induce current in those wires and, well, that's where most of the surge on the power lines (and cable TV, and phone lines, etc.) comes from. It's not direct, like that farmer in the country I talked about, but one can get anywhere from 1000 to 15,000 volt spikes induced on wires Not Actually Physically Touched by lightning. Rise times in the 1 us to 20 us range; fall times in the 20 us to 50 us range, sometimes a bit of a decaying oscillation, sometimes not. (Remember all those PhD's monitoring things? They found out stuff...)

But then, one runs into the other thing about lightning surges: They just don't hang around on the wires, they radiate. As in, electromagnetic emissions, like radio or light. The higher the frequency, the better the radiation. (This is why if one is listening to an AM radio during a thunderstorm, one will see the flash and hear the Spotz! on the radio at the same time). Just like throwing a rock into a pond: Big Splash at Ground Zero, not much left to see when one is 50' away. And that's pretty much where a lot of lightning energy goes: Into space. And that's assuming that it is actually free space.

If one's service cables are buried: The actual earth, of which the planet is made, is fairly conductive and absorbs energy from lightning like there's no tomorrow. The place where I currently live happens to have buried utilities. A lightning strike would have to hit the pole for the development, through a couple hundred feet of buried power cable, through step-down transformers (which are not known for easily passing high frequencies), before the energy hit the meters/breaker panels on the various houses. By the time the energy from a strike did all that, it'd be absorbed, period.

Conclusion: If you've lived in your place for N years and don't know of anybody in the area who's been hit by lightning; if you're at the bottom of a hill (or at least off the peak); you're surrounded by 60' trees that tower over everything (and perhaps none of them have signs of being hit..), the distribution wires are underground; then I truly wouldn't worry about it. If Thor has been out and about in your neighborhood and People Have Stories, then maybe cough out some $$ for a whole-house surge protector. But for $DIETY's sake, not that Eaton thing, which won't do anything for you. Talk to an Electrician.

 

[MikeHolliday]

This is an odd question that came to mind from an observation this evening:

Someone turned on a dryer this evening and I noticed a subtle dimming on a ceiling light.

I assumed it was a fluctuation in power from the dryer turning on, and, after half a second, everything was fine.

If something similar happened while my Model 3 was charging on the Gen 3 Wall Charger, would it cause any harm? I’d assume both the wall charger and the Tesla are robust enough to avoid any harm, since the former is properly grounded/installed, and the Tesla can resist most surges on its own. I just wanted to verify.

Overthinking it further, I imagined if the charger was limited to 32A and there was a slight fluctuation and the Amperage dropped for a few moments and suddenly came back up, is it safe to say the Charger would suppress any surge attempting to go above 32A? Or would it be the Tesla suppressing any surge? Or is it a combo of both?

Thanks for your patience in reading all that, and also for any assistance you can give me in understanding this.

That happens many times in a home with an undersized breaker panel, ie. Load Center. Did anyone do load calculations to see if your breaker panel was large enough to handle your charging?

 

[agmonaco]

I had a lightning strike a tree in front of my house. I live on a hill. The lightning went throught the ground and found my powerline to my well pump and not only burned it up but also burned up tv's in my house. I may need a surge protector on my 50 amp 14-50 outlet me thinks. Or make sure if there is thunderstorms in the area to unplug.

 

[Tronguy]

So, there you are:

• On a hill? Check.
• Have had personal acquaintance with Thor? Check.
• Have a seriously expensive piece of hardware hooked up, at least intermittently, to city power? Check.

Disconnecting your car when a thunderbumper rolls on by does make some sense on the face of it, in what’s not connected to city power can’t be affected by it. But, no offense, I question your ability to get out there and unplug the car each and every time a storm rolls by. Heck, for that matter, there really do exist “Bolts out of the blue”, usually from far-away storms, that show up unexpectedly. Not to mention times when you’ve left the car plugged in, then gone to bed, or a nap, or a walk. Or something that makes you Not There when a thunderstorm shows up.

It’s a risk vs. reward situation, with mid 5-digit costs riding on the question. Not to mention the other costs: anything big enough to fry a Tesla isn’t going to do anything else electric in your house any favors, either.

If you’re that worried about it (don’t take me wrong, that may be a legit worry), then, seriously, I’d suggest a whole-house lighting protector, and not that stupid thing from Eaton. Something with spark gaps and such that, literally, goes either before or right after the meter. My guess is that something like this costs around a grand, but you’ll need to talk to a real electrician to get an idea.

 

[Stanwood Steve]

I had a lightning strike a tree in front of my house. I live on a hill. The lightning went throught the ground and found my powerline to my well pump and not only burned it up but also burned up tv's in my house. I may need a surge protector on my 50 amp 14-50 outlet me thinks. Or make sure if there is thunderstorms in the area to unplug.

I also live on top of a hill, and had a large fir tree hit by lightning that was about 20 feet from the north end of my home. The electrician came to the same conclusion you did. It traveled up my ground rods into my home electrical supply and blew out my double oven, satellite receivers, all three garage door openers, and one TV. Each of the garage door opener mother boards were visibly fried. I had a whole house surge protector installed, although they say "lightning never strikes twice..." With my luck, I'll get hit again. The fir tree was killed too - the base of it was all burned at ground level so I had it removed but I have others just as high around it. All utilities in our development are run underground, by the way.

 

[PianoAl]

If I'm awake, I unplug when lightning gets very close, but we rarely have thunderstorms (like three per year). If we had more, I probably wouldn't do it.