The current reliability state division can not distinguish auxiliary equipments' working state with light defects. In this article

the operation states of auxiliary equipments are divided into healthy operation state and unhealthy operation state. The unhealthy operation state is classified into insufficient output type

friction and jam type

plug leakage type and lack of performance

according to different failure mechanisms. On the basis of analysis on fault data of the auxiliary equipments in 34 thermal power units

this paper puts forward the identification standard of the above four kinds of unhealthy operation states. The state division for auxiliary equipments based on unhealthy service status can reflect the degree of operation reliability accurately and provide the evidence and assurance for equipments management by the application in two power plants.