ABB RER620, Technical Manual

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1MAC309294-MB F
Section 4
Protection functions
RER620 147
Technical Manual
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
0
characteristic:
Table 164: Relay characteristic angle control in I
0
sin(φ) and I
0
cos(φ) operation criteria
Table 165: Characteristic angle control in phase angle operation mode
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
Operation criteria setting:
RCA_CTL
= FALSE
RCA_CTL
= TRUE
I
0
sin(φ) Actual operation criteria: I
0
sin(φ) Actual operation criteria: I
0
cos(φ)
I
0
cos(φ) Actual operation criteria: I
0
cos(φ) Actual operation criteria: I
0
sin(φ)
Characteristic angle setting
RCA_CTL
= FALSE
RCA_CTL
= TRUE
-90° φRCA = -90° φRCA = 0°
0° φRCA = 0° φRCA = -90°
A B C
C
0
ΣI
01
ΣI
02
-
ΣI
02
I
ef
R
0
L R
L
-
ΣI
01
0
V
0
V
0
V