A commenter here notes that detecting power lines is a really hard problem. However surely there is a set of simpler solutions to the problem than actually trying to spot power lines.

This sort of thing is a largely solved problem for bigger aircraft and a similar approach with quite a lot of international regulation and agreement seems to be needed.

Drones could be given a cross section of airspace to work within that is say a horizontal slice about 50m to 100m above ground level, with various rules on resolution (ie what constitutes ground level at any point on the planet). The minimum height should clear most obstacles that are hard to spot. There would be flight corridors defined between take off and landing zones. There would be exclusion zones around areas such as air fields and military locations etc.

Drones could even be allowed to use commercial airspace provided they follow the existing rules and are detectable and contactable etc.

The tricky bit is working out take off and landing zones and rules for them. At the moment, aircraft try to avoid flying over habitation zones. I live near to a helicopter factory and used to work there so I have some idea of the issues involved.

There are lots more rules that could be added for safety. For example, requiring height when flying in a non corridor depend on direction. However, I'm only allowing a 50m zone here but then a drone is only about 1m "tall". Even something as simple as divide the compass up into say 16 zones for wind Beaufort 0-2, eight zones for 3-4, four zones for 5-6 and ban flight at 7+. Those wind designations might depend on gust speeds or constant and could be transmitted. The idea is that things get a bit random as the wind speed increases. Divide the allowable height by the number of zones and set your height accordingly. So flying directly north will be at say 50m and directly south at 100m. The wind speed should also indicate the density of drones allowed per horizontal area. That will need some experimentation and legislation to determine what is "acceptable".