Analog Channel Configuration; Operation Principle - ABB RELION REX640 Technical Manual

1MRS759142 C
4.6.2.4
4.6.2.5
REX640
Technical Manual
and high df/dt and the activation of LSHDPFRQ. 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.

Analog channel configuration

LSHDPFRQ has one analog group input which must be properly configured.
Table 814: Analog inputs
Input
U3P
See the preprocessing function blocks in this document for the
possible signal sources.
There are a few special conditions which must be noted with the configuration.
Table 815: Special conditions
Condition
U3P connected to real measurements
Improper analog channel configuration causes a validation error if the analog
channels are not completely configured or they do not match with certain settings. For
troubleshooting, check the contents of this chapter and also the preprocessing blocks
in this document. The configuration can be written to the protection relay once the
mismatch is corrected.

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.
Protection functions
Description
Three-phase voltages
Description
The function requires that at least one phase or
phase-to-phase voltage channel is connected.
Section 4
847