The causes leading to non-scheduled shutdown of turbo-generator sets in one power generalion Co Ltd from 2004 to 2008 due to relay protection failures

including causes from the secondary circuits

from relay protection

from excitation systems

and from man-made factors

etc.

have been analysed

and some recommendations being put forward

such as importance shoud be attached to management of the secondary circuits and the excitation systems

as well as periodic replacement of fuses on the primary side of volatage transformers

and importance has to be attached to periodic inspection and simulation test of quick-acting cut-off and spare automatic put-in devices etc.