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.
If the current amplitude falls below one percent of the nominal current, the
direction enters the non-directional area.
Section 4
1MRS240050-IB C
Protection functions
192
REF615R
Technical Manual
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