The installed capacity of renewable energy resources in dc format is increasing in modern power systems, and thus, the protection of high-power dc power delivery from fault is critical in HVdc transmission and MVdc distribution networks. Based on thyristors, Z-source circuit breaker (ZCB) is a promising device for high-power protection, with the capabilities of bidirectional power flow and automatic/controllable turn-off function. In this article, a new specific method for calculating Z-source capacitances is developed based on the reverse-recovery characteristics of SCR, which was not considered in the prior-art solution properly. The proposed method can ensure the turn-off action of SCR in ZCB's practice for realistic dc network protection. At first, it is revealed that the problem in the prior-art solution of ZCB parameter identification, which does not handle the SCR's reverse recovery well, and thus, could result in a failure of tripping action. To solve the problem, the specific method is proposed to adjust the Z-source capacitances, in order to accumulate enough electrons for the postfault depletion region buildup in SCR, and thus, guarantee the SCR's turn-off for a successful dc circuit protection. In the specific derivation, the required tripping time of ZCB is also considered and can remain unaltered after Z-source capacitance adjustment. Finally, experimental tests have verified the problem solving by comparing the proposed to the prior-art solution and proven its accuracy. The proposed method can be added as a supplement to the prior-art solution for the practical design of ZCB. This research article helps to increase the technology readiness level of ZCB solution and practice in realistic dc network protection.