Power Line realities.
As background I've worked in the UK electrical supply industry for 35 years, most of that dealing with powerlines.
In that time I've also been involved with helicopter patrolling so know the view from above as well.
Most single wires are, as you know, difficult to see from above, believe me they can be hard to see from below and at night, even when we know where they are, almost impossible without powerful torches.
It seems that all the lighting on helicopters (landing lights) are designed for that purpose - they point down!
Without a very strict and methodical proceedure there is, in my view, little or no chance of a pilot spotting overrunning lines at night.
What actually are these wires?
Taking the UK system and excluding transmission lines (those on pylons)
They can vary in the main from about 3/8ths inch diameter up to 1 inch
They can be: -
High Cadmium copper, - very stretchable and difficult to snap (I've seen this type brought to the ground by trees, when the tree is removed, the wires spring back up to 20ft with no problem
Hard Drawn copper, not as stretchy but generally only break due to the effects of electrical arcing, otherwise ratchet or hydraulic cutters (and a bit of effort) are needed
Hard Drawn and pure aluminium, these are easier to cut for the small sizes
Steel Cored Aluminium, usually a minimum of 5 strands of high tensile steel wire surrounded by aluminium, even hydraulic cutters struggle on the larger sizes and need frequent blade changes!,
Transmission line wires BTW are more often than not steel cored aluminium, sizes go up the 400mm squared.
There is often talk of "detecting" power lines by electronic means by measuring the Electrical & Magnetic Field, you'll find that in the majority of cases on distrubution lines you will need to be close to get any reading above background levels, and you will only detect them by the rate of change of the readings.
National Grid EMF - Power lines: typical magnetic fields
National Grid EMF - Power lines: typical electric fields
As with most things avaiation the Mk 1 eyeball, correct proceedures & an understanding of what you are dealing with are the only solutions!