GE L30

9-12 L30 Line Current Differential System GE Multilin
9.4 INSTANTANEOUS ELEMENTS 9 APPLICATION OF SETTINGS
9
Figure 9–5: MAXIMUM ERROR FOR 50 HZ SYSTEM
To secure instantaneous element operation, it is recommended to use either FlexLogic as shown next to block the instanta-
neous elements during synchronization, or to use a different setting group with more conservative pickup for this brief inter-
val. A 700 ms drop-off timer in the logic is shown as an example to guarantee error below 3 percent, but delay can be
realistically even shorter, if the setting security margin allows this.
Figure 9–6: FLEXLOGIC TO BLOCK INSTANTANEOUS ELEMENT DURING 87L STARTUP
831792A2.CDR
AND(2)
OR(2)
87L DIFF PFLL FAIL
87L DIFF CH1 FAIL
87L DIFF CH2 FAIL
OR(2)
NEGATIVE ONE SHOT
TIMER 2
AND(2)
TIMER 1
= BLOCK INST (VO5)
0 ms
50 ms
= BLOCK INST (VO5)
0 ms
700 ms