ABB 615 series Technical Manual page 418

Section 4
Protection functions
412
Maximum torque line
forward direction (RCA = 0˚)
Forward
area
Minimum
operate current
Backward
area
Maximum torque line
reverse direction (RCA = 0˚)
GUID-CA5E7641-C50F-4303-B101-70181A1F3071 V1 EN
Figure 198: Definition of the relay characteristic angle
The phase angle difference is calculated based on the Characteristic angle setting (also
known as Relay Characteristic Angle (RCA) or Relay Base Angle or Maximum Torque
Angle (MTA)). The Characteristic angle setting is done based on the method of
grounding employed in the network. For example, in case of an ungrounded network, the
Characteristic angle setting is set to -90°, and in case of a compensated network, the
Characteristic angle setting is set to 0°. In general, Characteristic angle is selected so that
it is close to the expected fault angle value, which results in maximum sensitivity.
-VG (Polarizing quantity)
IG (Operating quantity)
Forward
area
Zero torque line
Backward
area
VG
1MAC059074-MB A
615 series ANSI
Technical Manual