When you see its by the electric lines do you mean the DC lines. I was walked from the first carriage of a southbound DC line train to the NLL high level and I couldnt see one.
A few months ago I do remember seeing an oyster validator on the northbound platform. Logically the oyster validator should be before you enter the stairs frmo the DC lines to the NLL. This makes it easier for everyone but I strongly suspect that they sited these validators in suspicous locations because they want to chop (eat) the money so that they can make lots of money !