According to the new challenges for the operation and maintenance of secondary localized equipment in power system

from the view of its external characteristics of hardware

the electrical and physical characteristics of the AC input connectors

power input interfaces

fiber channels

binary input circuits

operating indicators and external environment conditions are analyzed. Meanwhile

the on-line monitoring and diagnosis methods are also presented. According to the diagnosis of hardware external characteristic

the hardware interface state matrix is built and the typical fault diagnosis result is produced.