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
b2
I
d1
I
d2
I
b3
I
d3
100
200
300
100 200 300 400 500
End section 2End section 1
Low operate value
Section 1 Section 2 Section 3
I
d
[%Ir]
I
b
[%Ir]
Figure 392: 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
Slope section 2
and
Slope section 3
are determined correspondingly:
Slope section
I
I
d
b
2 100
2
2
= ⋅ %
(Equation 163)
Protection functions
1MRS759142 F
690 REX640
Technical Manual
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