Cross-tree

Image: © Bob Harvey Taken: 18 Apr 2021

The top of Image Note that the three phases are only insulated by a single ceramic disk, not a stack. I don't know the installation in detail, but I suspect this is 11kV or 6.6KV local distribution. There will be a small transformer station in the village to reduce this to the domestic 240V. It can't already be at that voltage as there is no neutral connection. The downfeed cables also hint at the higher voltage. They are shielded: that is each core is jacketed with a conductive sheath, which is earthed - you can see the little pigtails joining those shields together. This is not done for 240V lines. Notice, too, the insulating blocks in the two straining wires at the back of the pole. The wire is looped twice through those so that there is no direct electrical path in the stay. This would appear unnecessary - the upper end of the stay is not attached to the live parts in any way. But this is a sensible precaution against storm damage - any stray part becoming detached and flapping round the post cannot earth itself down the backstay. There is evidence in this one fenland electricity pole of a century of experience and best practice. The sort of thing that makes our electricity supply reliable in operation and relatively safe for the maintainers.

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