ABB RELION 620 Series Technical Manual page 860

Section 5
Protection related functions
5.7.4.3
854
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
The actual fault location must be identified using additional information, for example,
short circuit current indicators placed on tapping points.
GUID-312EE60E-1CB9-4334-83BD-39DF3FC5815E V3 EN
Figure 443: Fault on a distribution line with spurs
Trigger detection
The fault distance estimate is obtained when SCEFRFLO is triggered. The triggering
method is defined with setting Calculation Trg mode. The options for selection are:
"External" or "Internal", where the default value is "External". The TRIGG_OUT
event indicates fault distance value recording moment. The fault distance estimate, Flt
distance, together with the timestamp 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 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 is timed suitably to provide sufficient distance
estimation calculation time before tripping of the feeder circuit breaker.
• In case of internal triggering, the TRIGG 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 Distance estimate Va (in the same unit as the
fault distance estimate). When successive estimates during one fundamental
cycle are within "final value ± Distance estimate Va", the fault distance estimate
(mean of successive estimates) is recorded. In case stabilization criterion has not
been fulfilled, the fault distance estimate is given just before the phase currents
are interrupted. The phase selection logic is a non-directional function, and thus
internal triggering should not be used when directionality is required.
1MRS757644 F
Figure 443).
620 series
Technical Manual