ABB RELION 620 Series Technical Manual page 213

1MAC504801-IB E
620 series ANSI
Technical Manual
Characteristic angle
= -90 deg
maximum torque line
(operating quantity)
GUID-67BE307E-576A-44A9-B615-2A3B184A410D-ANSI V1 EN
Figure 91: Definition of the relay characteristic angle, RCA=–90 degrees in an
isolated network
Directional ground-fault protection in an isolated neutral network
In isolated networks, there is no intentional connection between the system neutral point
and ground. The only connection is through the line-to-ground capacitances (C
phases and leakage resistances (R
capacitive and has a phase shift of –90 degrees compared to the residual voltage (-V
Consequently, the relay characteristic angle (RCA) should be set to -90 degrees and the
operation criteria to "IoSin" or "Phase angle". The width of the operating sector in the
phase angle criteria can be selected with the settings Min forward angle, Max forward
angle, Min reverse angle or Max reverse angle.
current is defined in isolated neutral networks.
For definitions of different directional ground-fault characteristics, see
Directional ground-fault
- V (polarizing quantity)
0
Max forward angle
I
0
Min forward angle
zero torque line
). This means that the zero-sequence current is mainly
0
Figure 92
principles.
Section 4
Protection functions
Min reverse angle
Max reverse angle
Min operate
current
) of
0
describes how the ground-fault
).
0
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