Backup Overcurrent Function (O/C Backup); System Logic - ABB RELION REB500 Technical Manual

Section 5
Bay protection functions
5.1.7.4

Backup overcurrent function (O/C Backup)

The distance protection function includes a definite time overcurrent unit as backup
protection. A starting signal Start O/C is set to logical
I , and I
L2
to the system logic is set to logical
Blocking signals generated by the distance, underimpedance starting, power swing blocking
or VT supervision functions do not influence the backup overcurrent function.
The overcurrent function is independent of the distance protection starters and, not having to
perform phase selection, can have a more sensitive setting.
5.1.7.5

System logic

Structure of the system logic
The system logic processes the binary input signals from external plant (optocoupler inputs)
and all the binary signals of the distance protection function.
IEC19000420 V1 EN-US
Figure 19: System logic in the distance protection function
The system logic outputs are binary signals for controlling a disturbance recorder, LED signals
and auxiliary tripping and signaling relays.
Enabling and disabling logic (SUPBL)
The logic of the VT supervision function (VTSUP segment) has already been described in the
relevant Section. The external blocking signals for distance protection [EXTBL_DIST] (opto-
68
exceed the setting of
L3
© Copyright 2019 ABB. All rights reserved
1 , when one or more of the currents I
I O/C . After the time O/C Delay, the tripping signal Trip O/C
1 .
18000018-IEC19000420-1-en.vsdx
1MRK 505 406-UEN B
GUID-4A4F2D83-D04E-4142-BC6C-D7B9D20D0FD0 v1
GUID-1AF2E4BA-F6B1-4611-A4DA-ED64F2D7C3A4 v1
GUID-8513CE77-ACA6-47B3-82D3-9AFE624C370B v1
Bay protection functions REB500
Technical manual
,
L1