[tharkun__]

This. Same timeframe and I've lived through both lots of lightning storms and in areas with lots of power failures. Some of them intermittent and essentially caused by transformers blowing up. Like earlier this winter, we had multiple storms where you'd hear a transformer blow up, in many cases even seeing the sky light up as well from it, power going out, couple seconds, power coming back, next transformer blowing out, rinse, repeat.

On the other hand I've read about plenty of stories of the "cheap" UPSs you'd usually buy as a consumer (not to name any brands coz I've never had any) actually causing such issues in the first place. Without any actual surges from the grid.

That said, being totally not superstitious (for real, but someone's gonna "kill me" if they find out I wrote this and something dies from a surge...), now I guess I need to knock on wood like seventeen times ...

I do use surge protectors when we're on generator power temporarily.

[ssl-3]

The things people often call "transformers blowing up" are usually not transformers blowing up.

Instead, it's usually just overhead wires that are too close or literally touching, often from influences like wind and ice. The electricity arcs between the wires, creating bright blue-white flashes that can be seen from far away, sometimes with instantaneous heat that makes hunks of metal wire evaporate explosively. It can be violent and loud, and repetitious as different parts of even a single run fail.

Transformers can certainly blow up, but that's less common. They're (generally) filled with oil for cooling purposes, and they're massive things that tend to take time to get hot. A failed transformer can produce arcing and blue-white light, but if things are that hot then the oil is also ready to burn.

And when the oil burns it isn't blue-white -- it burns with about the same yellow-orange color we saw the last time we accidentally flambéed dinner on the kitchen stove, or a Hollywood fireball.

A bright flash without a fire is probably not a transformer.

Here's a video of a transformer actually-exploding (note the prominent fireball): https://www.youtube.com/watch?v=oFkfd31Wpng

And here's a video of what someone describes as a transformer exploding, even though there are no transformers in the video: https://www.youtube.com/watch?v=rHVh0KwG_0k

[tharkun__]

Haha, I hear you. But yes, it really is transformers blowing up sometimes. Sometimes it really is just branches blowing up the line, sure.

A branch hitting a wire, happenes all the time here too. Lots of trees in this community. The video of a transformer you shared: that's not the transformer I'm talking about. That's at a transformer station.

I'm talking transformer on a street pole. The kind that hangs right across the street from me. This kind: https://www.youtube.com/shorts/y3E7avUvj6I

See it's the kind in your second video. It's a transformer. You just chose a narrower definition I suppose. It's a https://en.wikipedia.org/wiki/Distribution_transformer ;)

And yes, I know it's transformers and not just wires (but also wires do happen definitely) coz I do walk the neighborhood regularly and I can tell when a transformer is new vs. old up there. Ours is old. The ones a few streets over sometimes are very new and I see the Hydro trucks go by the next day(s) to make them new ;)

Again, like seventeen times knock on wood but the ones next to us have not actually blown up. But three streets over, seen the new ones. Literally last weekend, we had an ice storm come through and while no blowouts we could see or hear, the outage map showed plenty of failure.

[freeone3000]

Residental-scale transformers can and do explode. Shorts happen not-infrequently with freezing rain and ice storms especially causing issues - the internal oil gets displaced by the water, and the dirty water causes an internal short. It wipes out power to a few blocks here when it happens, but we get an outage due to it every year or two.

[ssl-3]

They can. They do.

But when the wind is whipping along on a warm day and there are bright flashes and audible bangs, that's (usually!) not signs of transformers blowing up... even though the popular vernacular often erroneously describes it that way.

[LorenPechtel]

It happens. The power company was very unhappy with my boss for destroying one of their transformers. The thing is while circuit breakers react very quickly to extreme overcurrent situations (shorts) they're much slower to react to loads which are only a bit over the limit, and if short enough won't react at all. Very common with heavy motors.

And that's exactly what the problem was--we had a whole bunch of really heavy motors. Getting ready to start for the day you flip on the switches and the big machines start to spin. The transformer on the pole was rated higher than the main breaker for the plant--but the transformer apparently was more sensitive to the temporary loads. Once the problem was identified it was resolved by staging it, instead of flipping them all on they were flipped on over 5 minutes.

[pseudohadamard]

It's not just cheap UPSes, it's cheap surge protectors as well. They exist because the vendor can throw in a MOV costing a few cents and increase the price of the power strip by 50%, not because they're any good. MOVs are sacrificial components which have either degraded to uselessness by the time they're actually needed or, if they're still working, can explode or catch fire from the energy dissipated. Even if they don't, all they're doing is converting an x-kV spike on active into an around-x-kV spike on neutral or ground. If you want to do it properly, use a series tracking filter, not a "surge protector".

[tharkun__]

No offense, but can you tell me how my 4.5 kW generator is gonna generate that kind of power surge?

[tlb]

One scenario: there's a short circuit somewhere, say rats chewing through insulation. This can cause a very high current through the short. A non-inverter 4500 watt 120 volt generator might have 0.2 ohms coil resistance, so the short circuit current can hit 170 volts / 0.2 ohm = 850 amps. When the shorted branch's circuit breaker trips, the inductance in the generating windings wants to keep that 850 amps flowing for at least a few microseconds, and it gets distributed across everything else that's still connected. Depending on what else is connected (hopefully including some surge protectors) the peak voltage can get into many kilovolts.

The circuit is something like this:

  voltage source -- parasitic inductor --+- circuit breaker -- short
                                         |
                                         +- circuit breaker -- your PC

[pseudohadamard]

More generally, for the previous poster, look at what happens when a magnetic field collapses suddenly, you can get kilovolt spikes. There's probably a ton of YouTube videos demonstrating this in various ways, it sounds like the sort of thing that Electroboom would do. Normally this is handled via snubber circuits which dissipate the energy before it can do anything, but in exceptional cases it could end up going where it shouldn't.

[burnt-resistor]

Definitely use quality surge protectors on expensive equipment connected to generators.

PSA: UPSes and GFCI/GFI extension cords won't work properly when connected to a stand-alone generator with a bonded neutral. I've tried using enterprise UPSes on such generators, but they absolutely won't work. In such scenarios, debond the generator's ground from neutral, apply a very large warning label to it being debonded, and drive a massive ground rod electrode into the ground as close to the generator as possible and ground the neutral there. This does work and is much safer because there's a stable voltage reference source. It's more of a hassle but can be necessary for some off grid and temporary scenarios.

[ssl-3]

GFCI works correctly either way. Their operating mode doesn't care at all about ground: Whether bonded, not bonded, or not even present (look, ma! only two wires!), they still perform the same way.

They respond to an imbalance in current flow betwixt line and neutral. What goes out must return; if it doesn't, then switch off.

Ground is not part of the equation at all.

[jcalvinowens]

That extra unbonded ground rod is the worst thing you can possibly do to make your generator vulnerable to lightning strikes.

[burnt-resistor]

That's an extreme edge-case and a strawman. Anyone operating temporary equipment on a generator during a severe storm will obviously unplug sensitive stuff to not take unnecessary chances regardless of safety precautions already in place.

Ground rods are required in certain situations according to the NEC.

Ground rods are for lightning protection, transient surges (over voltage), and induced surges; not for short protection, ground faults, or making ordinary extension cord use of bonded generators "safer".

Typically, they're required whenever it's a system that powers a building on its own, i.e., off-grid setup or with a floating neutral generator connected via a switched neutral transfer switch.

[jcalvinowens]

You can unplug everything and open all the switches, but a nearby lightning strike will still fry your generator through that unbounded ground rod. Lightning ground potential is very eager to take the shortcut to your other ground rods through a few millimeters of insulation and open switches on the path through your generator and house wiring, when the alternative might be tens of meters of dirt :)

I don't care what the NEC doesn't say, NFPA 780 says you have to bond all ground rods.

[mschuster91]

> In such scenarios, debond the generator's ground from neutral

eeeeep. Please for the love of all that is holy, CONTACT AN ELECTRICIAN before messing around with that - or before creating a ground bond where none should be (i.e. TT grid [1]). You may end up endangering yourself if you do not exactly know what you are doing - in the case of TT, you get ground potential difference current from other parts of the grid flowing to ground via your generator's bond. Best case you're getting problems with electrochemical corrosion (including in your foundation), worst case enough current flows to turn your bond wire into a thermal fuse.

Also, take great care if your grounding is provided via municipal water service, or if your original grounding rod has dried out to the point it's ineffective.

Let me repeat: LET ELECTRICIANS DEAL WITH GROUNDING AND SURGE PROTECTION. Floating grounds and improper ground connections CAN BE LETHAL OR POSE A SERIOUS FIRE RISK.

AND YES THAT INCLUDES "ISLAND" SCENARIOS OR EMERGENCY POWER INPUTS (e.g. via CEE plugs and transfer switches).

[1] https://de.wikipedia.org/wiki/TT-System

[dboreham]

I'm not sure I'd leave something like this to an electrician. Or if so at least make that electrician be experienced in this field. I think you'd want an electrical engineer to be involved with the plan to some degree.

[Kirby64]

Electrical engineers don’t know code requirements and wiring guidelines for household electrical wiring. They’re absolutely not the correct default. Electricians with specialization in generator setups, sure, but an electrician engineer on average is likely going to be more uninformed on code requirements than an electrician.

[mschuster91]

Electrical engineers know the theory but lack the practical knowledge which grid form is used at your specific address (yes, here in Germany we have a few towns where one half side of a street runs TT and the other one is already migrated to TN-C or TN-C-S).

An electrician specializing in lightning protection, uninterruptible power installation or in radio installations can sort out all of that far better than an engineer can.