GE L60 Instruction Manual page 313

Line phase comparison system, ur series
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5 SETTINGS
c) NEUTRAL INSTANTANEOUS OVERCURRENT (ANSI 50N, IEC PIOC)

PATH: SETTINGS
GROUPED ELEMENTS
 NEUTRAL IOC1
MESSAGE
MESSAGE
MESSAGE
MESSAGE
MESSAGE
MESSAGE
MESSAGE
The neutral instantaneous overcurrent element may be used as an instantaneous function with no intentional delay or as a
definite time function. The element essentially responds to the magnitude of a neutral current fundamental frequency pha-
sor calculated from the phase currents. A positive-sequence restraint is applied for better performance. A small portion
(6.25%) of the positive-sequence current magnitude is subtracted from the zero-sequence current magnitude when forming
the operating quantity of the element as follows:
The positive-sequence restraint allows for more sensitive settings by counterbalancing spurious zero-sequence currents
resulting from:
System unbalances under heavy load conditions
Transformation errors of current transformers (CTs) during double-line and three-phase faults.
Switch-off transients during double-line and 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 how test currents are injected into the relay (single-phase injection:
I
0.9375xI
; three-phase pure zero-sequence injection:
=
op
injected
SETTING
NEUTRAL IOC1 FUNCTION:
Disabled=0
Enabled=1
SETTING
AND
NEUTRAL IOC1 BLOCK:
Off=0
SETTING
NEUTRAL IOC1 SOURCE:
_0
GE Multilin

SETTING GROUP 1(6)
NEUTRAL IOC1
FUNCTION: Disabled
NEUTRAL IOC1 SIGNAL
SOURCE: SRC 1
NEUTRAL IOC1
PICKUP:
1.000 pu
NEUTRAL IOC1 PICKUP
DELAY:
0.00 s
NEUTRAL IOC1 RESET
DELAY:
0.00 s
NEUTRAL IOC1 BLOCK:
Off
NEUTRAL IOC1
TARGET: Self-reset
NEUTRAL IOC1
EVENTS: Disabled
×
(
)
I
3
I_0
Kx I_1
where K
=
op
SETTING
NEUTRAL IOC1 PICKUP:
RUN
3( _0 - K _1 ) PICKUP
Figure 5–90: NEUTRAL IOC1 SCHEME LOGIC
L60 Line Phase Comparison System
5.5 GROUPED ELEMENTS

NEUTRAL CURRENT
NEUTRAL IOC1(4)
Range: Disabled, Enabled
Range: SRC 1, SRC 2, SRC 3, SRC 4
Range: 0.000 to 30.000 pu in steps of 0.001
Range: 0.00 to 600.00 s in steps of 0.01
Range: 0.00 to 600.00 s in steps of 0.01
Range: FlexLogic™ operand
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
1 16
=
I
3 I
×
).
=
op
injected
SETTINGS
NEUTRAL IOC1
PICKUP DELAY :
NEUTRAL IOC1
RESET DELAY :
t
PKP
t
RST
5
(EQ 5.18)
FLEXLOGIC OPERANDS
NEUTRAL IOC1 PKP
NEUTRAL IOC1 DPO
NEUTRAL IOC1 OP
827035A4.CDR
5-175

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