ABB RELION REF615R, Техническое руководство

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maximum torque line
Min forward angle
Min reverse angle
Min operate
current
Max forward angle
Max reverse angle
zero torque line
N
on-operati
ng area
Characteristic angle
= -90 deg
(operating quantity)
- (polarizing quantity)
0
V
0
I
GUID-67BE307E-576A-44A9-B615-2A3B184A410D-ANSI V1 EN
Figure 84: 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
0
) of
phases and leakage resistances (R
0
). This means that the zero-sequence current is mainly
capacitive and has a phase shift of -90 degrees compared to the residual voltage (-V
0
).
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 . Figure 85 describes how the ground-fault
current is defined in isolated neutral networks.
For definitions of different directional ground-fault characteristics, see
Directional ground-fault principles .
Section 4
1MRS240050-IB C
Protection functions
180 REF615R
Technical Manual