The economical

stable and efficient operation of power systems is intrinsically linked to secondary systems and their diverse functional applications. With the advancement of communication technologies

control algorithms

and emerging regulatory entities

modern power systems have evolved to become more intelligent yet complex compared to traditional grids. As the conceptual framework of power system security expands from primary system safety to a holistic cyber-physical paradigm

the functional safety of secondary systems has emerged as a critical and paramount requirement for ensuring overall grid stability and reliability. This paper systematically reviews research on functional safety analysis and mitigation strategies for secondary systems from a cyber-physical perspective. Firstly

the basic concept and propagation mechanism of power system functional security are introduced; secondly

the research difficulties of functional security are analysed from the three dimensions of system

data and software security; then

the current research status of functional security in different dimensions is summarised; finally

we offer a forward-looking perspective on future research directions for analysing and mitigating functional safety risks

emphasising the prevention of physical grid failures caused by secondary system anomalies from a cyber-physical viewpoint.