ABB Relion 670 series, Technical Reference Manual

Page: 146 / 1232

1. Output OPENCT provides instant information to indicate that open CT circuit has
been detected
2. Output OPENCTAL provides time delayed alarm that the open CT circuit has
been detected. Time delay is defined by setting parameter tOCTAlarmDelay .
3. Integer output OPENCTIN provides information on the local HMI regarding
which open CT circuit has been detected (1=CT input No 1; 2=CT input No 2)
4. Integer output OPENCTPH provides information on the local HMI regarding in
which phase open CT circuit has been detected (1=Phase A; 2= Phase B; 3= Phase
C)
Once the open CT condition is declared, the algorithm stops to search for further open
CT circuits. It waits until the first open CT circuit has been corrected. Note that once
the open CT condition has been detected, it can be automatically reset within the
differential function. It is not possible to externally reset open CT condition. To reset
the open CT circuit alarm automatically, the following conditions must be fulfilled:
• Bias current is for at least one minute smaller than 110%
• Open CT condition in defective CT circuit has been rectified (for example, current
asymmetry disappears)
• Above two conditions are fulfilled for longer time than defined by the setting
parameter
tOCTResetDelay
After the reset, the open CT detection algorithm starts again to search for any other
open CT circuit within the protected zone.
5.1.2.5 Binary signal transfer
There is space for eight binary signals integrated in the telegram of the line differential
analog communication. For further information, refer to section
"Binary signal
transfer" .
5.1.2.6 Line differential coordination function LDLPDIF (87L)
Line differential coordination function (LDLPDIF, 87L) is a support function to Line
differential protection functions L3CPDIF(87L), L6CPDIF (87L), LT3CPDIF (87LT)
and LT6CPDIF(87LT) . The function gathers and coordinates local IED signals and the
signals from remote IEDs between the Line differential protection functions and the
LDCM communication module.
The function acts as the interface to and from Line differential protection.
Section 5
1MRK505222-UUS C
Differential protection
140
Technical reference manual