The PhD project focuses on the investigation of quality degradation inflicted by technical debt and its cross-system network effects on a system-of-systems level. At present, the concept of technical debt is primarily regarded as an internal system phenomenon. Thus the mutual influences and interdependencies in complex systems are hardly investigated (if at all). The aim of the dissertation is the development of a cross-system quality framework for the evaluation of the system-of-system quality using the Smart Grid domain as an example. This model should enable the evaluation the system "health" of a Smart Grid from the perspective of systems engineering and be able to derive recommendations for action.