ABB RELION REX640 Technical Manual page 462

Protection functions
Figure 260: Earth-fault situation in a compensated network
The Petersen coil or the earthing resistor may be temporarily out of operation. To
keep the protection scheme selective, it is necessary to update the
angle setting accordingly. This can be done with an auxiliary input in the protection
relay which receives a signal from an auxiliary switch of the disconnector of the
Petersen coil in compensated networks. As a result the characteristic angle is set
automatically to suit the earthing method used. The RCA_CTL input can be used to
change the operation criteria as described in
Table 532: Relay characteristic angle control in Iosin(φ) and Iocos(φ) operation
criteria
Operation mode setting:
Iosin
Iocos
Table 533:
Characteristic angle setting
-90°
0°
Use of the extended phase angle characteristic
The traditional method of adapting the directional earth-fault protection function
to the prevailing neutral earthing conditions is done with the
setting. In an unearthed network,
compensated network
method of the network is temporarily changed from compensated to unearthed
due to the disconnection of the arc suppression coil, the
setting should be modified correspondingly. This can be done using the setting
462
RCA_CTL
Actual operation mode: Iosin
Actual operation mode: Iocos Actual operation mode: Iosin
Characteristic angle control in phase angle operation mode
RCA_CTL
φ
RCA
φ
RCA
Characteristic angle is set to 0 degrees. In case the earthing
Table 532
and
= FALSE
= FALSE
= -90°
= 0°
Characteristic angle is set to -90 degrees and in a
1MRS759142 F
Characteristic
Table 533
.
= TRUE
RCA_CTL
Actual operation mode: Iocos
= TRUE
RCA_CTL
φ = 0°
RCA
φ = -90°
RCA
Characteristic angle
Characteristic angle
REX640
Technical Manual