ABB 650 series, Техническое руководство

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6. For as long as the external fault persists an additional temporary trip condition is
introduced. That means that REFPDIF (87N) is temporarily desensitized.
7. If point P (Ibias, Idiff) is found to be above the operate - restrain characteristic), a
directional check can be made. The directional check is made only if (3I0) is more
than 3% of
IBase . If the result is an external fault the internal trip request is reset. If
the directional check cannot be executed, then direction is no longer a condition for
a trip.
8. When neutral current, residual current and bias current are within some windows and
some timing criteria are fulfilled, the ratio of 2
nd
to fundamental tone is calculated. If
it is found to be above 60% the trip request counter is reset and TRIP remains zero.
9. Finally, a check is made if the trip request counter is equal to or higher than 2. If it is
and that at the same instance of time t
REFtrip
, the actual bias current at this instance of
time t
REFtrip
is at least 50% of the highest bias current Ibiasmax (Ibiasmax is the
highest recording of any of the three phase currents measured during the disturbance)
then REFPDIF (87N) sets the output TRIP to 1. If the counter is less than 2, the TRIP
signal remains 0.
6.2.8 Technical data
Table 38: REFPDIF (87N) technical data
Function Range or value Accuracy
Operate characteristic Adaptable ± 1% of IBase if Ibias < 1.25 IBase
(i.e. base sensitivity in section 1 of
the operate - restrain
characteristic)
± 2% of theoretical operate value
(Idiff) if Ibias >= 1.25 IBase (i.e.
sections 2 and 3)
(The above is valid if IBase is equal
to the protected winding rated
current.)
Reset ratio 0.95 -
Directional characteristic, for
zero sequence directional
function
ROA ± 60 to ± 90 degrees ± 1 degrees at Ibias = IBase
± 2 degrees at Ibias = 2 * IBase
± 3 degrees at Ibias = 4 * IBase
(The above is valid if IBase is equal
to the protected winding rated
current.)
Operate time, trip function 25 ms typically at 0 to 10 x IdMin -
Reset time, trip function 30 ms typically at 10 to 0 x IdMin -
Section 6
1MRK 502 048-UUS A
Differential protection
128
Technical manual