ABB RELION REX640 Technical Manual page 439

1MRS759142 C
REX640
Technical Manual
Iocos(φ) criterion selected, reverse-type fault
=> FAULT_DIR = 2
GUID-89556830-D43E-4629-AB42-5492912B8FC9 V1 EN
Figure 233: 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
Protection functions
433