On 12/10/2020 10:13, JohnP wrote:
Looking down a hole - as I do - there are some modifications being done to
cables at a nearby substation. Some of the old cables are being extended
with "twisted three" cables rather than the usual three phases in a
circular outer.

Any ideas why?

as he said. its cheaper, and you only need an outer when you need
additional protection on the outside, or to carry an earth potential..

--
"When a true genius appears in the world, you may know him by this sign,
that the dunces are all in confederacy against him."

Jonathan Swift.