Measurement Modes - ABB RELION REX640 Technical Manual

Section 11
General function block features
11.6
1704
at 0.2 xFn or 0.11 xIn or 0.06 xUn at 1.5 xFn). As the Synchronism and energizing
check (SECRSYN) bus voltage U12b voltage input always expects Rated frequency,
the frequency adaptivity does not apply for this input.
If the generator terminal positive-sequence voltage is below the minimum level, the
relay is not able to maintain frequency adaptation. The non-adaptive situation is
indicated by function Protection output FRQ_ADP_FAIL. When frequency
adaptivity uses backup frequency source, the FRQ_ADP_BU output is activated. The
tracked frequency is retained for 3 seconds until the FRQ_ADP_FAIL output is
activated and Rated frequency is expected. Outputs FRQ_ADP_FAIL,
FRQ_ADP_BU and FRQ_ADP_WARN can be used in the application configuration, if
necessary.
See function block Protection for more information.
The operation accuracy of the protection functions in the range of 0.2...1.5 xFn can be
assumed to be according to the technical data given separately for each function.
Slight deviations in operation accuracy are possible outside the frequency range
specified in technical data. Operate time accuracy and reset times given in technical
data are only valid in the frequency range specified for each function.
The specified operate times are expected to increase at lower frequency due to longer
network cycles.
Frequency adaptivity depends on the availability of voltages or currents. The
generator start-up protection can be also extended by using wide peak-to-peak
measurement mode (operational from 2 Hz upward) with designated start-up
overcurrent protection function (PHLPTOC). Before the generator is connected with
the rest of the network by closing the circuit breaker, the designated start-up
overcurrent function should be either blocked or its start value increased, as the Start
value setting is typically lower than the nominal current.

Measurement modes

In many current or voltage dependent function blocks, there are various alternative
measuring principles.
• RMS
• DFT which is a numerically calculated fundamental component of the signal
• Peak-to-peak
• Peak-to-peak with peak backup
• Wide peak-to-peak
Consequently, the measurement mode can be selected according to the application.
1MRS759142 C
REX640
Technical Manual