These are used on 3 phase power distribution, 13.8kV between phases. The top hangs on a grounded messenger cable, and they use about 4 of these between poles.

This on the right
is used in pairs, forms a diamond pattern to hold the wires in an air spaced bundle.
This bundle at the top of this pole,
and using a different style of insulator. This pattern is supposed to survive storms better.

For the most part, crossarms are still in vogue here, though when street distributors are upgraded they are replaced with cluster cables for the ELV lines. 11kV and higher are still spaced on crossarms with separate insulators or put underground.

In new subdivisions, everything is underground to stop wind damage, though this is more expensive than installing poles because of the digging and the uprated cable sizes.

In WA Western Power have adopted a mix of the above with bundled 22kV street feeders in areas of lots of trees.

Been doing that for about 5 years and seems to have sorted out many issues of the past during lightning storms when 22kV lines have been brought down.

Lindsay

Being in a rural location where there are hundreds of miles of bare wire aerials, that type of hanger would present a massive risk in the fire season: It would be like California. The cost of fully insulated cable over a long distance would be enormous. Bare wire is common as it can carry the greatest current.

With the bare wire LV aerials here (now phased out) I always use 2m cross arms to ensure that without a separator in the middle of the span: The wires would not hit. That is also what needs to happen with any bare wire aerial: In strong wind & we had 126km/h 19th December 2017; The bare wires must not clash.

How often in a cyclone (twister etc) do you see wires clashing & arcing. In the middle of summer here, that would start a fire and has. Unfortunately flying debris cannot be fully protected against.

If I add 240VAC to 240VAC from 3phase I get something around 415V (Cos theta sneaks in: Its a vector sum)

Had a closer look at the 22kV feeders in my street using the above mentioned insulators and the actual conductor in use here is clad with either black nylon or plastic.
When the cable ends get to the pole mounted switchgear you can see (with a pair of binoculars) where the insulation ends and the bare conductor emerges to be terminated under clamps.

All up a much safer setup in areas of lots of trees such as where I live replacing many Kms of bare conductor 22kV overhead feeder and the crossarm with 2 insulators & the third directly on top of the pole.

A couple of years back a large gum tree blew over in quite high winds during the night and in doing so flicked a bare conductor 22kV feeder nearby and the resulting shower of hot metal set fire to the tinder dry grass.

That coupled with the very strong winds that night created a blaze that scared the hell out of many people in the semi rural area as it roared towards them at 3am in the morning.
2 or 3 properties were badly burnt up and luckily nobody was killed but the fire took about 5 days to get under control being in quite hilly terrain & thus difficult to get at & extinguish fully.

So maybe these insulated 22kV feeders are a step in the right direction and being bunched up close together reduces the risk of being banged together enough to rupture the insulation when a tree going down whacks the line.

Western Power are using LOTS of that sort of feeder now.

I think that comes down to a balance with cost, risk factor & maintenance. Insulated wire is much the same as buried stuff when current is involved. I would be interested in the fire properties of the insulation?

E.g. I know with the transformer insulation here even in the thirties, it was not allowed to support combustion.

The design of the bare wire private overhead aerials here, was good in terms of spacing in 54 years there was never a wire clash.

Marc

On most cabling in Australia, the PVC insulation and sheath will burn if put to a source of heat but it won't support combustion. If the heat is removed the flame goes out. Whilst a lot more expensive, there are heat and flame resistant offerings, which replace pyro and ceramic insulated cables of yesteryear.

Quite a lot of the old Glass & Ceramic here has been replaced. The new 16kV transformer (old failed: Oil leak) has no ceramic & all insulators on that pole (1962) and the cross-arm have been replaced in the last five years.