A loaded underground power cable dissipates some power as heat which heats the surroundings. The following scenario is possible in regions where large amounts of snow accumulate on the ground during winter.
At some point (late autumn or early winter) temperature gets below water freezing point. Snow starts accumulating. Then in spring temperature rises and snow starts melting. Loose heat from a cable line can be enough to accelerate melting of snow right above the cable line. The same scenario can happen if there's sudden warm weather in winter - recently accumulated snow starts melting.
This may cause the following curious observation: you're in some field or forest, everything is covered in snow, expect a narrow trace running across that area where snow has melted to the ground. The power cable is immediately traceable.
I've also heard that sometimes cables are not plotted on publicly available location plans and this is done to keep the cables secret (some government organizations might do that, I have no evidence of that, let's just assume this happens). Clearly leaking heat which melts snow and makes the cable traceable in warm weather makes it hard to keep the cable location secret. Spotting and plotting such cable requires no special equipment and no special skills - just take a GPS tracker in your pocket and walk the trace and if anyone questions you - then say you're going for a walk.
How can a cable line be designed such that it doesn't leak heat enough to make it traceable in the scenario above? An underground cable is covered with at least half meter of ground and even that is not enough. Obviously adding more thermal insulation would reduce the effect but not eliminate it completely.
How could one design a cable line that doesn't leak heat to ground surface?
