I'm sure you know there's a length limit on USB - about 5m / 200 inches. It's so short that running a USB cable from my 3rd floor apartment to the ground would have been out of spec. If TED insists on transmitting signals in the form of noise on your electrical lines, then I think an 85 foot extension cord is the way to go.
You could take your ammeter to a metrologist and get it professionally calibrated...
Anyway, I hope your TED gives you some very good data to share.