Function Block - ABB Relion Technical Manual

1MRK 502 048-UUS A
6.4.3
6.4.4
Technical manual
Adaptive frequency tracking is included to ensure proper operation of the generator
differential protection during varying frequency conditions.
An open CT circuit condition creates unexpected operations for Generator differential
protection under the normal load conditions. It is also possible to damage secondary
equipment due to high voltage produced from open CT circuit outputs. Therefore, it may
be a requirement from security and reliability points of view to have open CT detection
function to block Generator differential protection function in case of open CT conditions
and at the same time produce the alarm signal to the operational personal to make quick
remedy actions to correct the open CT condition.
Generator differential protection GENPDIF (87G) is also well suited to generate fast,
sensitive and selective fault clearance, if used to protect shunt reactors or small busduct.

Function block

GENPDIF (87G)
I3PNCT* TRIP
I3PTCT* TRIPRES
BLOCK TRIPUNRE
BLKRES TRNSUNR
BLKUNRES TRNSSENS
BLKNSUNR PICKUP
BLKNSSEN BLKH
DESENSIT OPENCT
OPENCTAL
IDMAG_A
IDMAG_B
IDMAG_C
IDMAG_NS
IBIAS
ANSI07000025-2-en.vsd
ANSI07000025 V3 EN
Figure 49: GENPDIF (87G) function block
Signals
Table 44: GENPDIF (87G) Input signals
Name Type
I3PNCT GROUP
SIGNAL
I3PTCT GROUP
SIGNAL
BLOCK BOOLEAN
BLKRES BOOLEAN
BLKUNRES BOOLEAN
Table continues on next page
Default Description
- Neutral side CT input
- Terminal side CT input
0 Block of function
0 Block of trip from the restrained diff. protection
0 Block of trip from unrestrained diff. prot.
Section 6
Differential protection
133