Posted by Martin Connelly on 11/01/2019 10:09:46:
Were they all put in at the same time? Methods, regulations and materials change with time so some parts may be to later regulations. Old setups may be left untouched until a repair is done at which point the latest regulations will apply.
Martin C
As Martin says, it is most likely that the line all the way from the pole transformer was originally bare wires but that work on the high voltage line (or at least the transformer pole) has been carried out later. Possibly refurbishment / replacement which would include replacing the low voltage wires with insulated Aerial Bunched Conductor (ABC) at that pole. The rest of the low voltage line could have been replaced at the same time, but cost or company policy or technical constraints may have meant that the minimum was done.
Stuart