Phase selection
GUID-F5513F63-3A6F-4981-AF34-6B92F2828581 v1
The phase selection logic determines the loop:
•
for the underimpedance starting measurement when an ground fault has been detected
•
to be measured in the first period (max. 20 ms) after starting
•
to be measured during the time the function is in the picked-up state when a ground fault
has been detected on an ungrounded system or system with Petersen coils (phase
selection ≠ solidly grounded)
In a solidly grounded system (parameter
PhaseSelMode set to solid gr.), the loop to be
measured is determined according to the following table:
Table 48: Solidly grounded system- loop to be measured
Type of fault
Starters
Loop measured
Phase-to-ground fault
L1, E
L1E
Phase-to-ground fault
L2, E
L2E
Phase-to-ground fault
L3, E
L3E
Phase-to-phase fault
L1, L2
L1L2
Phase-to-phase fault
L2, L3
L2L3
Phase-to-phase fault
L3, L1
L3R
Phase-to-phase-to-ground fault
L1, L2, E
L1L2
Phase-to-phase-to-ground fault
L2, L3, E
L2L3
Phase-to-phase-to-ground fault
L3, L1, E
L3L1
Three-phase fault
L1, L2, L3
L3L1 (L1L2) (L2L3)
In a solidly grounded system, both phases involved in a phase-to-phase-to-ground fault have
to trip, which is not the case in ungrounded systems or systems with Petersen coils. The
phase-to-phase loops are measured.
In ungrounded systems or systems with Petersen coils (parameter
PhaseSelMode set to cyclic/
acyclic phase selection), the loop to be measured is determined according to the following
table:
Table 49: Ungrounded system or Peterson coil - loop to be measured
Type of fault
Starters
Loop measured
Phase-to-phase fault
L1, L2
L1L2
Phase-to-phase fault
L2, L3
L2L3
Phase-to-phase fault
L3, L1
L3L1
Three-phase fault
L1, L2, L3
L3L1 (L1L2) (L2L3)
Cross-country fault *)
L1, L2, E
according to phase
selection logic
Cross-country fault *)
L2, L3, E
Cross-country fault *)
L3, L1, E
*) two ground faults at different locations
In ungrounded systems or systems with Petersen coils, it is usual for just one of the two
ground faults of a cross-country fault to be tripped, so that as much of the system remains in
operation as possible.
1MRK 505 406-UEN B
Section 5
Bay protection functions
Bay protection functions REB500
57
Technical manual
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