We have all seen this phenomena, in the early morning or late afternoon -  when the sun is “against the day”  - the sun somehow reflects off  the wires and makes them shine like illuminated spider’s webs.  

Now the wires are usually insulated with black plastic (pvc) and are round in section - wouldn’t you think that the wires would not act like lenses and concentrate the light to the point that the wires appear luminescent?  In fact  I would think that the roundness would act to disperse the light - like the curves on a stealth aircraft do with radar.

What is the phenomena that makes the wires intensely bright?