ABB RELION 670 Series Applications Manual page 117

1MRK 505 337-UUS A
blocked as soon as the total incoming current exceeds the pre-set level. By appropriate setting
then it can be insured that this sensitive level is blocked for external phase-to-phase or three-
phase faults, which can cause CT saturation. Comparison between these two characteristics is
shown in figure 50.
Diff Oper Level
Sensitive Oper Level
IEC06000142 V1 EN-US
Figure 50: Differential protection operation characteristic
Additionally the sensitive differential protection can be time delayed and it must be externally
enabled by a binary signal (that is, from external open delta VT overvoltage relay or power
transformer neutral point overcurrent relay).
The setting parameters for the check zone are set via the local HMI or PCM600.
Such check zone is included in the IED. By a parameter setting
Connected can be decided, individually for every bay, if it shall be connected to the check zone or
not. This setting is available in bay function block.
For every zone there is a setting parameter
Disabled . This setting parameter determines if the individual zone shall be supervised or not by a
check zone. This setting is available in both Zone functions. Finally the check zone shall be enabled
(that is, setting parameter
zone. Operating characteristics for the check zone can be set independently from the two
discriminating zones.
However, it is to be observed that the check zone has slightly different operating characteristic
from the usual discriminating zones. For the check zone the resultant outgoing current is used as
stabilizing current instead of total incoming current in order to guarantee the check zone
operation for all possible operating conditions in the station. The check zone operating
characteristic is shown in figure 51:
Application manual
Sensitive
differential
protection
Operate
region
Sens Iin Block
s=0.53
CheckZoneSup , which can be set to Enabled or
Operation shall be set to Enabled ) in order to fully enable the check
Differential protection
Differential protection
operation characteristic
I [Primary Amps]
in
en06000142.vsd
CheckZoneSel = NotConnected /
Section 6
M12474-3 v3
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