Surge protector is a lie?

[Commander Kinsey]

Well one I fitted at my work (a little plug in one by something like Techtronics) melted into a lump and drew enough current to trip a 32A breaker. It saved a roomfull of stuff from 415V.

[Commander Kinsey]

I have a 2kW fanheater by Micromark and it seems to be fine. Had it for years and used it loads of times. Cuts out nicely when it gets clogged with dust too.

[trader_4]

That isn't the case. As I pointed out previously, whole house surge protectors rated at 50K amps are connected via a 20A breaker. A fuse isn't effective, by the time the fuse blows from high current, the high voltages of the surge will have reached the appliance and done the damage.

That's how MOVs work.

Many appliances have something like this inside, I'm told but never

Electronic appliances do.

Did they have surge protection at the panel? I'll bet not. It's rare that much energy makes it into a building, typically it arcs and flashes over before that much can get there. And if you have surge protection at the panel, it can deal with what's left.

[Ralph Mowery]

The peak voltage on a 120 volt circuit is almost 1.5 times that. So the MOV needs to be rated for around 200 or slightly more volts or 400 volts if across the 240 volt lines. The MOVs are basically open circuits below the rated voltage and almost a short for any thing over the rated voltage.

[Commander Kinsey]

Surely a surge can come from all sorts. What if you live near a factory with massive motors? What if lightening strikes somewhere? The electricity board might have lightning arrestors, but I bet something still gets through.

[Commander Kinsey]

The 11kV to 240V transformer which serves around 100 houses is just over the road from me. No overhead wires on either side. Can't see any overhead wires anywhere except the 330kV ones from a coal power station, and I think 11kV to a farm, which has it's own pole transformer, but there's never both voltages in the same place.

[Commander Kinsey]

Since when did voltage get called tension?

[Commander Kinsey]

Why twist them? And why not use the better conducting and less brittle copper?

[Jasen Betts]

I think it was originally German thing: "Spannung"

[Carlos E.R.]

And Spanish: Alta tensión.

[upsidedown]

In an ABC cable the isolated aluminum phase conductors are twisted around an un insulated steel(alloy) neutral conductor. The steel wire handles most of the mechanical load and often survives a tree falling on the cable.

In a (nearly) balanced three phase cable, the neutral current is much smaller than the phase currents, thus the neutral connection can have a lower conductivity but better mechanical strength than phase conductors.

Aluminum has only slightly worse conductivity, is much lighter and cheaper as copper.

[Andrew]

And being lighter it means that 40+ old creosoted poles could have a longer life.

When ever copper prices are high there is a spate of replacing bare copper 240V stuff on poles with bundles of twisted insulated aluminium conductors. I guess it is also possible to have bigger section conductors for the same weight. Important with more people buying EV's, heat pumps and heated tubs /pools.

[Vir Campestris]

Hmm.

says copper is about 2/3 the resistance of aluminium, and elsewhere I find about 3 times the weight. so you'd halve the weight on the poles, but have fatter cables.

But...

Whenever I've seen a pole down it's after a gale. Strong winds, not cable weight, finish them off. So the fatter cable you'll need for ally will be more of an issue than the reduced weight.

Andy

[Rod Speed]

It isnt the wind drag on the cables that pulls the pole over.

[upsidedown]

If a tree falls during a storm on open wire copper lines, the flimsy wires will snap and the poles are saved. This of course cuts the electric distribution.

If a tree falls on a bundled cable (especially with a steel wire neutral), it is possible that the pole falls down, but the electric distribution may still continue, despite part of the cable has fallen to the ground.

[John Larkin]

A tree fell, down the block from our cabin. It sent a shock wave down the lines which tugged on our long feeder and ripped the wires off the front of the cabin, with the power and cable and old POTS wires on the ground. We didn't lose power or internet.

[Commander Kinsey]

So instead of the water analogy, they use an analogy of.... weightlifting?

[Jasen Betts]

maybe a drive chain.

[The Natural Philosopher]

if you have ever seen a good close up electrostatic discharge the idea of a stretched cable snapping is not far off

[Commander Kinsey]

Apparently I have to inform the power company when I install an EV charger. Like I'm gonna bother doing that.