ABB RELION REX640 Technical Manual page 932

Protection and control

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Protection functions

Start of operation timer

Figure 517: Load-shedding operation in the "Freq< AND df/dt>" mode when both

Freq< and df/dt conditions are satisfied ( Rated frequency=50 Hz)

Start value Freq set at 0.975 xFn

Start value df/dt set at -0.020 xFn/s

Operate Tm df/dt = 500ms

Operate Tm Freq = 1000ms

Load shed mode = Freq< AND df/dt

Start of operation timer

OPERATE is activated

as Freq< AND df/dt

condition satisfied

1MRS759142 F

Technical Manual