ABB RELION REX640 Technical Manual page 723

1MRS759142 F
algorithm does not eliminate the blocking at inrush currents unless there is a fault in
the protected area.
The feature can be enabled and disabled through the
Fifth harmonic blocking
The inhibition of the protection relay operation in situations of overexcitation is
based on the ratio of the fifth harmonic to the fundamental component of the
differential current (Id5f / Id1f). The ratio is calculated separately for each phase
without weighting factors. If the ratio exceeds the set value of
blocking is enabled through the
stage of the protection relay in the phase is blocked.
At dangerous levels of overvoltage which may cause damage to the transformer, the
blocking can be automatically eliminated. The blocking is removed if the ratio of the
fifth harmonic to the fundamental component of the differential current exceeds
the set value of the
deblocking feature can be enabled or disabled with the
Stop value 5. H
Start value 5. H
Figure 409: The fifth harmonic blocking limits and the operation when both
blocking and deblocking features are enabled through the Harmonic deblock 5.
setting
Fifth harmonic blocking has a hysteresis to avoid rapid fluctuation between TRUE
and FALSE. The required consecutive fulfillments of the condition can be counted
using the blocking counter. When the condition is not fulfilled, the counter is
decreased (if >0).
Also fifth harmonic deblocking (based on the higher limit,
with
consecutive fulfillments of the condition. When the condition is not fulfilled, the
counter is decreased (if >0).
Waveform blocking
The biased low stage can always be blocked with waveform blocking; it cannot
be disabled with
intended for external faults while the second is intended for inrush situations. The
algorithm has criteria for the low-current periods of differential current during the
inrush and external fault.
REX640
Technical Manual
Stop value 5.H setting, and the blocking removal is enabled. The
harmonic content / % of fundamental
hysteresis
hysteresis
5 th harmonic block
Harmonic deblock 5. ) has a hysteresis and a counter which counts the required
Restraint mode . This algorithm has two parts. The first part is
Restraint mode setting, the operation of the biased
1
0
Protection functions
Harmonic deblock 2. setting.
Start value 5.H and
Harmonic deblock 5. setting.
Stop value 5.H , if enabled
t
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