**2. Modeling of Understudy System**

Figure 1 shows the understudy 345 kV transmission line with the length of 200 km. The network had two buses that were connected to the power grid via two Thevenin equivalent voltage sources. The short circuit levels of the U1 and U2 equivalents were 10 GVA and 15 GVA, respectively. Additionally, the x/r ratio of the positive and zero sequences was 10 and 4, respectively. Table 1 shows the parameters of the single circuit transmission line for the positive and zero sequences. This transmission line was transposed and modeled as the frequency-dependent line in the EMTP software environment. The shunt reactor, as shown in Figure 1, had four windings and was grounded through an inductance to mitigate secondary arc current. The shunt reactor parameter calculations are expressed as follows for different cases.

**Figure 1.** The under-study 2-bus power system.

**Table 1.** The 345 kV transmission line with 200 km length.

