For most thermal power units

the 4 T/H steam extraction is used as the working steam source for turbine-driven feed-water pumps in normal operation condition of unit

but in designing the typical interlock protection logic of 4 T/H steam extraction

only the safe operation protection of turbine was considered

the special conditions

such as the local oscillation in power grid may cause many turbine-driven feed-water pumps to lose steam source at the same time

hadn't been considered

hence

affecting stability of the entire power gird.For this

a series of suggestions and measures for eliminating the said influence upon stability of the power grid have been put forward

so as to strengthen the coordination between the protection control of unit and the protection control of the power grid.