Analysis and solution for turbine trip problem during full power house load test at a nuclear power plant

The paper introduces the axial displacement protecting action triggered turbine trip problem during the full power house load test at a nuclear power plant. Through analysis and inspection. The direct reason for turbine trip is that the second medium-pressure control valve was jammed during the test, hence steam entered the medium-pressure cylinder to work, which caused the extra axial thrust that result in the monitored value of axial displacement was higher than the protection threshold value to trigger the turbine trip. The root cause of the turbine trip is that the design value of the assembling interval of the thrust ring of the medium pressure control valve is too small. (authors)