This paper introduces an accident of generator-transformer over-excitation inverse time protection misoperation
through analysis on the DCS system instructions and parameter
action reports
protection device verification
identifies the cause of this misoperation are that the reference value deviation of the generator-transformer over-excitation inverse time protection causes the protection to malfunction
which is the direct cause of the unit trip. At last
proposes the preventive measures after the analysis to avoid similar faults.