**4. Conclusions**

We have designed an improved DC circuit breaker taking into account external elements and the transmission line by expanding the conventional breaker technology. Due to the development of high-power transmission, the influence of the current on the external elements and the transmission line cannot be ignored. The DC circuit breaker in this paper uses a blocking inductor to reduce the load on the transmission line at the inverter stage and significantly reduce the amount of current flow through the rectifier stage based on the bifurcation point to protect the device and circuit. When determining the value of the ground inductor, ZCT and RST were found to have an inverse relationship, and the inductor was selected according to the optimal analysis methodology for the proposed DCCB design. In addition, verification of the individual switching elements was carried out in detail to confirm the use of each element in the DCCB. Moreover, the problem of energy dissipation, which is a concern due to the lack of a reverse charging process or a surge arrester, was solved by analyzing the ground voltage between the DCCB and the transmission line. The current flow mechanism has been analyzed to increase reliability and aid further research in the field of DCCB.

**Author Contributions:** Writing—original draft, G.K.; Investigation, J.S.L.; Formal analysis, J.H.P.; Supervision, M.J.L.; Writing—review & editing, H.D.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported in part by the National Research Foundation of Korea (NRF) gran<sup>t</sup> funded by the Korean governmen<sup>t</sup> (MSIT; gran<sup>t</sup> number 2018R1A2B600821613) and in part by the BK21 FOUR Program(Fostering Outstanding Universities for Research, 5199991714138) funded by the Ministry of Education(MOE, Korea) and National Research Foundation of Korea(NRF).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Not applicable.

**Acknowledgments:** The EDA tool was supported by the IC Design Education Center(IDEC), Korea.

**Conflicts of Interest:** The authors declare no conflict of interest.
