3.4.2. Energy Dissipation Verification

Figure 9a schematically shows the dissipation process in the proposed DCCB. The use of dissipative thyristors near ground in this DCCB is schematically illustrated in Figure 9c,d. Also, the measured node was expressed to verify the energy dissipation between the DCCB and the transmission line. The voltage measurement in Figure 9c represents the residual energy of the DCCB, and the residual energy of the transmission line is verified by the voltage measurement in Figure 9d.

**Figure 9.** Simulation of energy dissipation in the DCCB proposed in this paper (**a**) Schematic illustration of the DCCB diagram in the presence of the dissipative thyristor. (**b**) Current flow in the presence of the dissipative thyristor. (**c**) Graph of voltage between the DCCB and ground over time. (**d**) Graph of voltage between the main current branch and ground over time.

Figure 9b schematically shows the current flow after the main mechanical switch is turned off when there is a dissipative thyristor in Figure 9a. In the absence of a dissipative thyristor in the proposed DCCB, residual current will inevitably flow through the ground inductor to ground, resulting in ripple. As can be seen in Figure 9c,d, the value of this ripple is very small compared to the steady-state voltage. If you need to further reduce the ripple, turn on the dissipative thyristor after the main switch is turned off, so the current will not pass through the ground inductor. As shown in Figure 3b, when the fault current occurs in the opposite direction, as shown in Figure 3b, only the current flow from the DCCB to the ground passes through the dissipative thyristor.

Figure 9c shows the voltage between the DCCB and the ground. In the proposed DCCB, ZCT occurs within 1ms under simulated conditions and RST is less than 2 ms. Therefore, in order to independently analyze the use of the dissipative thyristor in the

energy dissipation process, the dissipative thyristor was turned on after 0.1 s (100 ms). Since the fault current did not occur 3 s ago, the voltage of the DCCB is the same as the voltage charged to the reverse charge capacitor under the normal steady-state. When the main switch is turned off and the energy dissipation process is reached, 99% of the voltage is lost to ground even without the dissipative thyristor, leaving little residual energy in the DCCB. Therefore, even without the surge arrester, the energy dissipation problem rarely occurs when the DCCB proposed in this paper is used. This small ripple can also be made to converge to zero by turning on the dissipative thyristor shown in Figure 9a. Analyzing the current at 4–4.1 s confirms that it converges to zero when the dissipative thyristor is turned on.

Figure 9d shows the voltage between the main current branch and ground. Figure 9d is very similar to the graph in Figure 9c. The voltage state is normal 3 s ago, when the main switch is turned off, the voltage decreases sharply. At this time, the proposed DCCB rapidly dissipates the energy equivalent to 98% of the energy seen under normal voltage conditions, similar to Figure 9c. This amount of loss doesn't cause much trouble but using a dissipative thyristor to converge the voltage to zero can completely eliminate the energy dissipation problem.
