RFL 9300 RFL Electronics Inc.
January 30, 2002 6-64 (973) 334-3100
6.7 DESCRIPTION OF INSTANTANEOUS OVERCURRENT BACKUP
TRIP ALGORITHM and INVERSE TIME OVERCURRENT BACKUP
TRIP ALGORITHM
The 9300 now implements an Inverse Time Overcurrent Backup Trip Algorithm (for Phase and Ground) in ad-
dition to the Instantaneous Overcurrent BackupTrip Algorithm (for Phase and Ground). These trip algorithms
are used only when the relay is in Backup Mode.
6.7.1 INSTANTANEOUS OVERCURRENT BACKUP TRIP ALGORITHM
Instantaneous Overcurrent Backup is always active in Backup Mode. This algorithm is implemented in the re-
lay using parameter #28 for phase and #29 for ground. The range of values for Phase Overcurrent Backup
(PH OC BU) is 6.0 amps to 31.875 amps. The range of values for Ground Overcurrent Backup (G OC BU) is
1.0 amps to 31 amps.
This instantaneous overcurrent function will enable trip during backup mode operations when two conditions
are met. First if the current exceeds the setting entered and second if the phase controller executing the over-
current algorithm has an active fault detector and there is at least one more fault detector active at the local
station.
6.7.2 INVERSE TIME OVERCURRENT BACKUP TRIP ALGORITHM
The Inverse Time Overcurrent Backup Trip Algorithm for phase and ground will be active during Backup Mode
only if the user has enabled the feature using parameter #30 for phase and/or #34 for ground (3I0). If no fur-
ther parameters are selected, the Inverse Time Overcurrent Backup Trip Algorithm will use default settings
for the pickup value.
The phase controller executing the Inverse Time Overcurrent Backup Trip Algorithm will enable trip if the cur-
rent remains above the pickup level until the TOC timer times out even without an active fault detector.
THIS IS A FUNDAMENTAL CHANGE IN CCS OPERATION WHICH WOULD OTHERWISE REQUIRE TWO
ACTIVE FAULT DETECTORS TO ENABLE TRIP IN EITHER THE INSTANTANEOUS OVERCURRENT
BACKUP MODE ALGORITHM OR IN THE PERMISSIVE TRIP ALGORITHM.
6.7.3 SETTING UP THE INVERSE TIME OVERCURRENT FUNCTION
The inverse time overcurrent feature can be enabled using the front panel display/keypad or via April Software
from a terminal or personal computer.
The Phase Time Overcurrent function is set for all three Phase Controllers, Phase A Phase B and Phase C
simultaneously as a group.
The Ground Time Overcurrent function for the 3I0 Controller is set separately and is completely independent
of the status or settings of the Phase Time Overcurrent function.
This allows the user to enable either the ground or phase time overcurrent functions separately or use them in
conjunction with each other with the same or different pickup values, dial settings and curves.
To Next Page
Loading...