occurred in the area protected by TR2PTDF. Then the internal blocking signals of the
biased stage are inhibited.
Instantaneous high stage
The instantaneous high stage operation can be enabled and disabled with the
Enable high set
setting. The corresponding parameter values are "TRUE" and
"FALSE."
The operation of the instantaneous high stage is not biased. The instantaneous
stage operates and the output OPR_HS is activated when the amplitude of the
fundamental frequency component of the differential current exceeds the set
High
operate value
or when the instantaneous value of the differential current exceeds
2.5 times the value of
High operate value
. The factor 2.5 (=1.8 × √2) is due to the
maximum asymmetric short circuit current.
If the biasing current is small compared to the differential current or the phase
angle between the winding 1 and winding 2 phase currents is close to zero (in a
normal situation, the phase difference is 180 degrees), a fault has occurred in the
area protected by TR2PTDF. Then the operation value set for the instantaneous
stage is automatically halved and the internal blocking signals of the biased stage
are inhibited.
Figure 274: Operating characteristics of the protection. (LS) stands for the biased
low stage and (HS) for the instantaneous high stage
The OPERATE output is activated always when the OPR_HS output activates .
The internal blocking signals of the differential function do not prevent the operate
signal of the instantaneous differential current stage. When required, the operate
outputs of the instantaneous high stage can be blocked by the BLK_OPR_HS and
BLOCK external control signals.
1MRS757644 H
Protection functions
620 series
Technical Manual
531
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