ABB RELION REX640 Technical Manual page 1214

Protection related functions
Taps or spurs in the feeder
If the protected feeder consists of taps or spurs, the measured fault impedance
corresponds to several physical fault locations (For example, A or B in
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example, short circuit current indicators placed on tapping points.
Figure 693: Fault on a distribution line with spurs
5.7.5.4 Trigger detection
The fault distance estimate is obtained when SCEFRFLO is triggered. The triggering
method is defined with setting
"External" or "Internal", where the default value is "External". The TRIGG_OUT event
indicates the fault distance value recording moment. The fault distance estimate,
Flt distance, together with the time stamp of actual triggering are saved in the
recorded data of SCEFRFLO.
• In case of external triggering, an external trigger signal should be connected
to the TRIGG_REC input. The triggering signal is typically a trip signal from
a protective function. At triggering moment the fault distance is stored into
recorded data. It is important that triggering be timed suitably to provide
sufficient time for the distance estimation calculation before tripping of the
feeder circuit breaker.
• In case of internal triggering, the TRIGG_REC input is not used for triggering.
Instead, the trigger signal is created internally so that the estimation is started
when Phase selection logic detects a fault and the estimate is triggered when
its value has stabilized sufficiently. This is judged by maximum variation in
fault distance estimate and defined with setting
same unit as the fault distance estimate). When successive estimates during
one fundamental cycle are within "final value ±
distance estimate (mean of successive estimates) is recorded. If the stabilization
criterion has not been fulfilled, the fault distance estimate is given right before
the fault ends. Phase selection logic is a non-directional function so internal
triggering should not be used when directionality is required.
Generally, SCEFRFLO requires a minimum of two fundamental cycles of measuring
time after the fault occurrence.
distance estimate of SCEFRFLO as a function of time.
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). The actual fault location must be identified using additional information, for
Calculation Trg mode . The options for selection are
Distance estimate Va (in the
Distance estimate Va ", the fault
Figure 694
illustrates typical behavior of fault
1MRS759142 F
Figure
REX640
Technical Manual