When I was a young teenager, I sometimes spoke to tech professionals, who were working on power-lines and/or telephone cables, the latter of which were strung above-ground from the usual telephone poles. Sometimes, those tech professionals were disposed to answer my curious questions.
What above-ground telephone cables had or have, is refrigeration stations at some of their connection-points, that refrigerate air to “-20⁰C”, which also makes the air very dry, and then to feed that air into the cables in compressed form. The purpose of this exercise is to prevent moisture buildup inside the telephone cables, that have hundreds of wires, if not thousands of wires.
Assuming that such a unit is being used, the question remains unanswered of how it’s supposed to work, if the outside air temperature is below -20⁰C. If the process continues, then air will be fed into the cables at a higher temperature than the ambient temperature, at which point technically, the air being fed in is also moister, than the saturation point of the ambient air. (:1) What could follow, is ice build-up in the cables, and, when the temperature outside rises suddenly, the ice can melt.
I’m not sure what the exact conductivities are, but think that liquid water conducts better than ice, so that liquid water can cause shorting of the telephone wires inside the cables. I suppose that if the ambient air stays warm long enough, continued feeding of cold, dry air into the cables can dry out the cables again…
(Updated 1/20/2019, 7h40 … )