Technical Data - ABB Relion Technical Manual

Section 6
Differential protection
6.2.8
128
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
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
time t is at least 50% of the highest bias current Ibiasmax (Ibiasmax is the
REFtrip
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.

Technical data

Table 38: REFPDIF (87N) technical data
Function
Operate characteristic
Reset ratio
Directional characteristic, for
zero sequence directional
function
Operate time, trip function
Reset time, trip function
nd
to fundamental tone is calculated. If
, the actual bias current at this instance of
REFtrip
Range or value
Adaptable
0.95
ROA ± 60 to ± 90 degrees
25 ms typically at 0 to 10 x IdMin
30 ms typically at 10 to 0 x IdMin
1MRK 502 048-UUS A
Accuracy
± 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.)
-
± 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.)
-
-
Technical manual