ABB RELION Series, Техническое руководство

Страница: 505 / 804

GUID-312EE60E-1CB9-4334-83BD-39DF3FC5815E V3 EN
Figure 259: Fault on a distribution line with spurs
5.4.4.3 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.
Generally, SCEFRFLO requires a minimum of two fundamental cycles of measuring
time after the fault occurrence.
Figure 260 illustrates typical behavior of fault distance
estimate of SCEFRFLO as a function of time.
1MRS758755 A
Section 5
Protection related functions
REC615 and RER615 499
Technical Manual