ABB RELION REX640 Technical Manual page 886

Section 4
Protection functions
880
X
GUID-E6D2705B-840A-4EDB-9839-5ACFF5ECB4E0 V1 EN
Figure 475: Impedance measured during a two-phase-to-earth fault
The available faulted loop selection logic schemes allow blocking the phase-earth
loop of the leading phase to prevent overreaching Ph Prf mode Lo Z GFC = "BLK
leading PE".
It is also possible to block the lagging phase-earth loop, Ph Prf mode Lo Z GFC =
"BLK lagging PE". If only the phase-to-phase loop or phase-to-earth loops must be
measured, settings Ph Prf mode Lo Z GFC = "PP only" or Ph Prf mode Lo Z GFC =
"PE only" should be used, and if the logic is not required, "All loops" option should be
selected.
The tables summarize the available faulted loop selection logic schemes and their
operations. The logic is selected with the Ph Prf mode Lo Z GFC setting.
Table 840: Supported faulted loop phase selection schemes for low-impedance earthed networks
and their influence on the RELEASE_PE monitored data
Element start All loops
A & B & AB Fault
EARTH_FLT
B & C & BC Fault
EARTH_FLT
C & A & CA Fault
EARTH_FLT
Lagging phase-to-earth loop
Phase-to-phase loop
Leading phase-to-earth loop
Ph Prf mode Lo Z GFC
PE only PP only
RELEASE_PE
AB Fault No fault
BC Fault No fault
CA Fault No fault
1MRS759142 C
R
BLK leading PE BLK lagging PE
BG Fault AG Fault
CG Fault BG Fault
AG Fault CG Fault
REX640
Technical Manual