Internet Upload Speed Drops at 7:00P.M. Everyday

For the past month i have had 4 techs out and also a maintenance order out at my house due to slow upload speeds and 4-8% packet loss. There is a light poll that turns on and off at night which back fed voltage and melted some wires. I seem to be having the same issue as the upload is fine until the street lights come on at around 7 o clock P.M.