IG
IGcos
Forward
tripping zone
Backward
tripping zone
-VG
Correction
angle
non-tripping
zone
Min operating
current
RCA
= 0 deg
GUID-FD40209E-1D00-4CF5-B593-B2DD971BA33F V1 EN
Figure 162: Operating characteristic Iocos(φ) in reverse fault
Phase angle 80
The operation criterion phase angle 80 is selected with the Operation mode setting by
using the value "Phase angle 80".
Phase angle 80 implements the same functionality as the phase angle but with the
following differences:
• The Max forward angle and Max reverse angle settings cannot be set but they have
a fixed value of 80 degrees
• The sector limits of the fixed sectors are rounded.
The sector rounding is used for cancelling the CT measurement errors at low current
amplitudes. When the current amplitude falls below three percent of the nominal current,
the sector is reduced to 70 degrees at the fixed sector side. This makes the protection more
selective, which means that the phase angle measurement errors do not cause faulty
operation.
There is no sector rounding on the other side of the sector.
Section 4 1MAC059074-MB A
Protection functions
346 615 series ANSI
Technical Manual
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