The research aims to define electrical architectures based on the rationalization of the distribution structure and of power sources with the achievement of the primary objectives of service continuity, power quality, safety and safe maintenance. The work consists of two parts: the first part deals with the architecture impact on a complex system analyzing the system configuration and operational safety aspects. New developments and methodologies are presented in the study of critical systems. A theory of complex systems for safety, operation and maintenance aspects is defined that enables to assist the management of the system throughout its whole life cycle and allows an implementation of programming languages. The second part refers to specific issues of mission critical power systems, data centers and hospitals especially. Several measurements were performed in laboratory and on field to analyze sneaky critical cases for the service continuity and the integrity of these strategic power systems.