Think of the static electricity you know, winter sweater, static electricity can be up to 10,000 volts, but the human body does not feel anything, is because of the short time, the current is small, the actual role of the product on the energy = Rt * I square, I and t is small enough, so the human body damage is small.
The same 4000V withstand voltage test, but the actual did not form an effective circuit, so the I is extremely small no bad. And normal loading 4000v at both ends of the power cord, I = U/R, high, the energy acting on the power cord is abnormally high, the power cord can not withstand