ABB RELION REX640 Technical Manual page 608

Section 4
Protection functions
602
The operating characteristic of the biased low stage is determined by Low operate
value, Slope section 2 and the setting of the second turning point of the operating
characteristic curve, End section 2 (the first turning point is fixed). The settings are the
same for all the phases. When the differential current exceeds the operating value
determined by the operating characteristic, the differential function awakes. If the
differential current stays above the operating value continuously for a suitable period,
which is 1.1 times the fundamental cycle, the OPR_LS output is activated. The
OPERATE output is always activated when the OPR_LS output is activated.
The stage can be blocked internally by the second or fifth harmonic restraint, or by
special algorithms detecting inrush and current transformer saturation at external
faults. When the operation of the biased low stage is blocked by the second harmonic
blocking functionality, the BLKD2H output is activated.
When operation of the biased low stage is blocked by the fifth harmonic blocking
functionality, the BLKD5H output is activated. Correspondingly, when the operation
of the biased low stage is blocked by the waveform blocking functionality, the
BLKDWAV output is activated according to the phase information.
When required, the operate outputs of the biased low stage can be blocked by the
BLK_OPR_LS or BLOCK external control signals.
I [%Ir]
d
300
200
100
I
d1
Low operate value
Section 1
End section 1
GUID-812B4AC0-1278-4637-B54E-53C616A46F52 V1 EN
Figure 333: Operation characteristic for biased operation of TR2PTDF
The Low operate value of the biased stage of the differential function is determined
according to the operation characteristic:
Low operate value = Id1
I
b2
I
d2
100 200
Section 2
End section 2
1MRS759142 C
I
b3
I
d3
300 400 500
Section 3
Technical Manual
I [%Ir]
b
REX640