Based on the analysis of unplanned outage of unit in Jiangsu electric power system for several years,finding out the main factors which affect the unplanned outage of unit,put forwarding the measures which can reduce the unplanned outage of unit,providing some methods to improve the reliability for generating unit in Jiangsu Electric power system.

Unplanned outage is one of important benchmarking content,and boiler "four pipe" leakage is the main reason caused unplanned outage in thermal power plant at long time,which influences safety and stable operation of generation equipments seriously.