According to relativity,nothing can break light barrier.But a recent [preprint](http://arxiv.org/abs/1101.1840) shows energy transmission of commercial electric power (f=60Hz) is faster than light. (It is not the drift velocity of electrons because energy transport depends on the electromagnetic field instead of charged particles). Moreover, the speed increases as its frequency decreases so the value is infinity for a direct current (f=0).That is action at a distance (instantaneous interaction)!

My question is whether it is possible to design a circuit to compare this speed with c in lab? For example,time-delay of an electromagnetic signal through a free space distance of 3m is $10^{-8}\text{ s}$. As to direct current along a copper wire, however, there should be no delay. Is the difference detectable? I'm interested to the experiment because it is of substantial significance to measure the rate of electric power for electrical engineering not matter the result can exceed c or not.