Leaking current better known as stray, comes from various sources, poor substation grounding, bad power distribution designs, shabby underground work.
Every year we get calls I am getting a shock when I walk in the back yard, or when I touch the chain link fence, usually when we get to the job we may find a backyard shed that has been wired by a DIYer, and it usually had shabby wiring with faults causing us to get stray readings.
Hope this helps you understand, leaking current.
