The power lines
I used to be a lineman. How low are these lines? The magnetic field around a high voltage line - say 340 KV - is about eight feet. We used to lean into them just to make sparks jump from our fingers. (I was in college, what did I know). But, we were 100 feet up a tower when we did that.
Around a secondary line, such as the one that takes power into your house, the field is much smaller. Are there buried lines by this substation?
If the field extends so far that you are feeling it, and granted I am not an engineer so there could be a logical reason, you might want to to call your local utility and tell them. Because if you can feel it, the danger is that will arc and you will become the shortest path to the ground. Not a pleasant thing. Yes, I know you have rubber tires which ground you, but if you step off the bike, or touch something, it could be ZAP!!!