Calculation of energy in transient overvoltages

It is argued that the calculation of the energy in a transient overvoltage using the time integral of V²(t)/Z, where Z has the default value of 50 Ω and the voltage, V(t), is that between the hot conductor in the AC line and ground, is inaccurate. A quantitative error analysis is presented that uses an artificial AC line network to simulate a long branch circuit and to give the impedance of the AC line as a function of frequency. A method for measuring energy dissipated in a varistor is advocated for use in future experiments. While measuring the energy in a varistor avoids many of the problems associated with the overvoltage energy, the energy dissipated in a varistor is also an underestimate of the total energy in the transient overvoltage