ABB RER620 Technical Manual page 153

1MAC309294-MB F
RER620
Technical Manual
A B
L R
L V
0
Figure 63: Ground-fault situation in a compensated network
The Petersen coil or the grounding resistor may be temporarily out of operation. To keep
the protection scheme selective, it is necessary to update the characteristic angle setting
accordingly. This is done with an auxiliary input in the relay which receives a signal from
an auxiliary switch of the disconnector of the Petersen coil in compensated networks or of
the grounding resistor in grounded networks. As a result the characteristic angle is set
automatically to suit the grounding method used. The RCA_CTL input can be used to
change the I characteristic:
0
Table 164: Relay characteristic angle control in I
Operation criteria setting:
I sin(φ)
0
I cos(φ)
0
Table 165: Characteristic angle control in phase angle operation mode
Characteristic angle
setting
-90°
0°
Usage of the extended phase angle characteristic
In addition to the RCA_CTL input, the extended phase angle characteristic can be used
when the compensation coil is temporarily disconnected in compensated networks. When
the extended operation area is used, the operation area is wide enough to detect ground
faults selectively in compensated networks regardless of whether the compensation coil is
connected or not. Therefore, the RCA_CTL input is not required if the extended operation
area is used.
Sometimes the distance between the start point and the relay is long which makes it
impractical to apply the scheme based on signal wiring between the relay and the Petersen
C
ΣI
01
C
0
ΣI
02
I
ef
sin(φ) and I
0 0
RCA_CTL = FALSE
Actual operation criteria: I
Actual operation criteria: I
RCA_CTL = FALSE
φRCA = -90°
φRCA = 0°
Section 4
Protection functions
R
0
ΣI
02
cos(φ) operation criteria
RCA_CTL = TRUE
sin(φ) Actual operation criteria: I
0
cos(φ) Actual operation criteria: I
0
RCA_CTL = TRUE
φRCA = 0°
φRCA = -90°
-
V
0
ΣI
01
-
V
0
cos(φ)
0
sin(φ)
0
147