ABB RELION 620 Series Technical Manual page 225

1MAC504801-IB E
620 series ANSI
Technical Manual
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
Protection functions
219