Power lines are a killer in this industry. Part of being an ISA Certified Arborist is attending an EHAP (Electrical Hazard Awareness Program) regularly.
When your tree is within the designated Minimum Approach Distance of the high voltage lines, I will guide you through the process of having the specialized trimmers through FPL come make it safe for a private company like me to work on it. They offer this for free.
There are 100 guys in town that will tell you that I'm being overly cautious and that they're not scared of working around those lines.
Next year there will be 99.
Don't take the risk!