Abstract: Power systems, critical for the mission of their loads (hospitals, data centers) and/or equalized to mission critical for the vulnerability of their supplying network, need a partition system, local fortified structure, interface between network and utilization, designed as a service continuity castle and managed to guarantee an adequate response to every emergency. This operational management must ensure the efficacy of the partition system in maintaining dependability and functional safety against the loss service continuity during fault events, maintenance demands and emergencies for external stresses. The system structure design can apply a 'Darwinian approach' aimed to mitigate also the external stresses and service losses against expected dangerous events such as hurricanes, earthquakes, fires and other events that can cause long blackouts from the main network. Preventive measures to reduce the earthquake consequences, predictable in that location, are based on the principles of controlling and mitigating the seismic stresses. A special power distribution, herein defined as 'brush distribution' are proposed for critical buildings exposed to seismic risks and for road tunnels with higher risk in case of fire event. The design of a power system requires a comprehensive and permanent design and highest consideration of competence of system maintenance operators.