GE Digital Energy L30, Instruction Manual, Page: 292 / 644

5-166 L30 Line Current Differential System GE Multilin
5.6 GROUPED ELEMENTS 5 SETTINGS
5
b) NEGATIVE SEQUENCE INSTANTANEOUS OVERCURRENT (ANSI 50Q, IEC PIOC)
PATH: SETTINGS

GROUPED ELEMENTS

SETTING GROUP 1(6)

NEGATIVE SEQUENCE CURRENT

NEG SEQ OC1(2)
The negative-sequence instantaneous overcurrent element may be used as an instantaneous function with no intentional
delay or as a definite time function. The element responds to the negative-sequence current fundamental frequency phasor
magnitude (calculated from the phase currents) and applies a positive-sequence restraint for better performance: a small
portion (12.5%) of the positive-sequence current magnitude is subtracted from the negative-sequence current magnitude
when forming the operating quantity:
(EQ 5.20)
The positive-sequence restraint allows for more sensitive settings by counterbalancing spurious negative-sequence cur-
rents resulting from:
• system unbalances under heavy load conditions
• transformation errors of current transformers (CTs) during three-phase faults
• fault inception and switch-off transients during three-phase faults
The positive-sequence restraint must be considered when testing for pickup accuracy and response time (multiple of
pickup). The operating quantity depends on the way the test currents are injected into the relay (single-phase injection:
; three-phase injection, opposite rotation: ).
Figure 5–74: NEGATIVE SEQUENCE IOC1 SCHEME LOGIC

NEG SEQ IOC1

NEG SEQ IOC1
FUNCTION: Disabled
Range: Disabled, Enabled
MESSAGE
NEG SEQ IOC1 SIGNAL
SOURCE: SRC 1
Range: SRC 1, SRC 2
MESSAGE
NEG SEQ IOC1
PICKUP: 1.000 pu
Range: 0.000 to 30.000 pu in steps of 0.001
MESSAGE
NEG SEQ IOC1 PICKUP
DELAY: 0.00
s
Range: 0.00 to 600.00 s in steps of 0.01
MESSAGE
NEG SEQ IOC1 RESET
DELAY: 0.00
s
Range: 0.00 to 600.00 s in steps of 0.01
MESSAGE
NEG SEQ IOC1 BLOCK:
Off
Range: FlexLogic™ operand
MESSAGE
NEG SEQ IOC1
TARGET: Self-reset
Range: Self-reset, Latched, Disabled
MESSAGE
NEG SEQ IOC1
EVENTS: Disabled
Range: Disabled, Enabled
I
op
I_2 K I_1 where K

–
1 8

= =
I
op
0.2917 I
injected

=
I
op
I
injected
=
FLEXLOGIC OPERANDS
NEG SEQ IOC1 FUNCTION:
NEG SEQ IOC1 PICKUP:
NEG SEQ IOC1 SOURCE:
NEG SEQ IOC1 BLOCK:
NEG SEQ IOC1 DPO
NEG SEQ IOC1 OP
NEG SEQ IOC1 PKP
RUN
AND
827058A5.CDR
SETTING
SETTING
Enabled=1
Disabled=0
SETTING
SETTING
I
_2
Off=0
SETTING
NEG SEQ IOC1
RESET DELAY:
NEG SEQ IOC1
PICKUP DELAY:
t
PKP
t
RST
I I
_2 - K _1 PICKUP