This model was proposed by the IEEE Working Group 3.4.11 and it is referred to a frequency-dependent model [2]. It is composed by two sections of nonlinear resistance, usually designated by A0 and A1, which are separated by a R-L filter, as shown in Fig. 4. For slow-front surges, the R-L filter has low impedance and the nonlinear resistances A0 and A1 are almost in parallel. However, for fast-front surges the impedance of the R-L filter is highest. As consequence of this, the current in nonlinear resistance A0 increases such as the voltage. Since characteristic A0 has a higher voltage than A1 for a given current (as shown in Fig. 5), the result is that the arrester model generates a higher voltage for fast transients (dynamic characteristics of the MOSA).