Surge protector is a lie?

Huh? Higher voltage power lines feed the input to the "Pole Pig" (the transformer on the pole) and lower voltage (240 V) power lines exit the transformer. Laterals are connected from those low voltage lines to houses. Maybe you can clarify what you mean by higher voltage and lower voltage?

Ed

The way this is done may vary between the US and UK. This is cross-posted to international groups.

Andy

And those wires are not strung between the same poles. The line feeding the house is strung from the pole pig (transformer) to the house. Maybe it's different where you are. In the US, the low voltage line is 240V, and the wire is not large diameter. So they can't run it very far without larger losses than is practical. If the houses are not so close together, they simply mount a transformer by each house. A single house on a transformer is not uncommon. So the transformer goes on the pole supporting the higher voltage lines, closest to the house. But even these "higher" voltage lines are not high voltage.

The transformer feeding my house also feeds the house next to me. It is less than 100 feet from either house. But then the lines are underground, so not much chance of a line cross.

Trouble is any decent surge would blow its internal fuse, which stops it protecting, and the surge then carries on to the equipment. A better way would for the fuse to also stop power to the device it's protecting. Then if the surge is too much for the surge protector, you've stopped the power to the device.

I'm going make my own, with varistors big enough to blow a 30A fuse for the whole ring main.

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.

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.

They are here. We don't have underground wiring, like you. Our utility is Consolidated Edison (Con Ed).

The high voltage line feeds many transformers; in my neighborhood each pole pig feeds many houses. The word "many" indicates a specification that Con Ed uses. They allow some number of transformers fed by a high voltage line and some number of houses fed by the secondary of a pole pig before another pole pig must be installed. There's also a distance spec; if a pole pig is serving less than the maximum number of houses and therefore could serve another house, the distance from the pole pig to the house must be within some maximum number of feet. If it isn't, then another pole pig must be installed on a pole closer to the house.

A few years back we had a "Northeaster" that knocked down a high voltage line that ran _between_ poles. The end of that wire was "dancing and prancing" on the ground; it melted the snow and burned a hole in the _dirt_ about

4-5 inches deep and maybe a foot in diameter. The houses served by the first pole pig all had power. The rest of the houses on the street served several other pole pigs were dark.

Here's a link where you can see the high voltage lines going from pole to pole - the same poles that have the low voltage (240V). The picture is about 1/2 way down in the document.

The line feeding the house is strung from the pole pig (transformer) to the house. Maybe it's different where you are. In the US, the low voltage line is 240V, and the wire is not large diameter. So they can't run it very far without larger losses than is practical. If the houses are not so close together, they simply mount a transformer by each house. A single house on a transformer is not uncommon. So the transformer goes on the pole supporting the higher voltage lines, closest to the house. But even these "higher" voltage lines are not high voltage.

That's why I asked for clarification. What are you calling "higher" voltage - the voltage that you say is not on or between utility poles?

Thanks, Ed

There seems to be some confusion regarding the terminology.

Most standards divide between low and high voltages around 1000 V.

However, in many standards the voltage range immediately above 1 kV is known as the medium voltage range, which typically extends to a few tens of kilovolts (e.g. up to 35 kV).

Big motors and power station generators operate typically at a few kilovolts.

Feeding the local distribution transformers are done with medium voltages in the 10-20 kV range. IIRC in the US 14 kV seems to be a common medium voltage feeding the pigs in the poles.

The problem with the low 120/240 V distribution voltage with a pig in every or every other pole is that you have to have medium voltage lines on every other street to feed the pigs. This may require using the same poles for both medium voltage feeds as well as low voltage feeds.

In the rest of the world with 230/400 V local distribution voltage, the distance between distribution transformers can be over 900 m, thus the number of transformers is much smaller and much simpler medium voltage network is required. Using open wires for the medium voltage and isolated ABC cabling for low voltage lines are common. Using ABC (aerial bundled cable) cabling also for the medium voltage cabling, you might even have medium voltage (top), low voltage (230/400 V) and ELV (e.g. telephone)bellow these in the same poles.

ABCs are also quite tolerant to falling trees, you might have one or two fallen trees against the ABC between two poles without disrupted. service. In severe cases, a pole might snap before the ABC is broken.

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.

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.

Since when did voltage get called tension?

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

I think it was originally German thing: "Spannung"

See the fifth picture (Typical North American utility pole)

And Spanish: Alta tensión.

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.

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.

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

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