Frayed wires on a Castle Island light post brought a South Boston pooch within inches of its life when it trotted through an electrified puddle, prompting calls for City Hall to find a solution for the potentially deadly “stray voltage” incidents.South Boston City Councilor Ed Flynn wants to have hearings on the dangers of stray voltage, whether a study into older, failing electric equipment is feasible, and what can be done to keep pets — and possibly people — from being seriously injured.