GE L90 Instruction Manual page 239

5 SETTINGS
• DD CONTROL LOGIC: This setting is used to prevent operation of I_0 and I_2 logic of Disturbance Detector during
conditions such as single breaker pole being open which leads to unbalanced load current in single pole tripping
schemes. Breaker auxiliary contact can be used for such scheme.
• DD LOGIC SEAL-IN: This setting is used to maintain Disturbance Detector output for such conditions as balanced 3-
phase fault, low level TOC fault, etc. whenever the Disturbance Detector might reset. Output of the Disturbance Detec-
tor will be maintained until the chosen FlexLogic™ operand resets.
The user may disable the
tem which may result in filling the events buffer and thus cause the possible loss of any more valuable data.
NOTE
SETTING
DD FUNCTION:
Enabled=1
Disabled=0
ACTUAL
COMPUTE SEQ.
CURRENTS
I_1
I_2
I_0
SETTING
DD CONTROL
LOGIC:
Off=0
SETTING
DD LOGIC
SEAL-IN:
Off=0
SETTING
DD NON-CURRENT
SUPV:
Off=0
GE Multilin
setting as the DD element will respond to any current disturbance on the sys-
DD EVENTS
LOGIC
DELTA LEVEL
DETECTOR
RUN
ABS (I_1-I_1')>0.04 pu
(I_1' is 4 cycles old)
ABS (I_2-I_2')>0.04 pu
(I_2' is 4 cycles old)
ABS (I_0-I_0')>0.04 pu
(I_0' is 4 cycles old)
LOGIC
ADAPTIVE LEVEL
DETECTOR
RUN
AND
I_0 > 0.12 to 0.24 pu
I_2 > 0.12 to 0.24 pu
NOTE:
ADJUSTMENTS ARE
MADE ONCE EVERY
8 CYCLES TO THE
NEXT LEVEL (HIGHER
OR LOWER) IN 0.02 pu
STEPS USING THE
HIGHEST VALUE OF
I_0 AND I_2.
AND
AND
Figure 5–91: DISTURBANCE DETECTOR SCHEME LOGIC
L90 Line Differential Relay
5.5 GROUPED ELEMENTS
OR
OR
OR
FLEXLOGIC OPERAND
50DD SV
OR
5
827044A6.CDR
5-149