This time delay can be set and it is used to prevent unwanted load-shedding actions
when the system frequency recovers to the normal level.
Throughout this document, “high df/dt” is used to mean “a high rate of
change of the frequency in negative direction.”
Once the frequency has stabilized, LSHDPFRQ can restore the load that is
shed during the frequency disturbance. The restoration is possible manually or
automatically.
The function contains a blocking functionality. It is possible to block function
outputs, timers or the function itself, if desired.
4.5.2.4 Operation principle
The function can be enabled and disabled with the
Operation
setting. The
corresponding parameter values are "On" and "Off".
The operation of LSHDPFRQ can be described using a module diagram. All the
modules are explained in the next sections.
Figure 224: Functional module diagram
1MRS758755 C
Protection functions
REC615 & RER615
Technical Manual
457
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