GE Multilin
T60 Transformer Protection System
5-195
5 SETTINGS
5.6 GROUPED ELEMENTS
5
c) NEUTRAL INSTANTANEOUS OVERCURRENT
(ANSI 50N)
PATH: SETTINGS
GROUPED ELEMENTS
SETTING GROUP 1(6)
NEUTRAL CURRENT
NEUTRAL IOC1(12)
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:
(EQ 5.37)
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:
; three-phase pure zero-sequence injection:
).
Figure 5–102: NEUTRAL IOC1 SCHEME LOGIC
NEUTRAL IOC1
NEUTRAL IOC1
FUNCTION: Disabled
Range: Disabled, Enabled
MESSAGE
NEUTRAL IOC1 SIGNAL
SOURCE: SRC 1
Range: SRC 1, SRC 2, SRC 3, SRC 4, SRC 5, SRC 6
MESSAGE
NEUTRAL IOC1
PICKUP: 1.000
pu
Range: 0.000 to 30.000 pu in steps of 0.001
MESSAGE
NEUTRAL IOC1 PICKUP
DELAY: 0.00
s
Range: 0.00 to 600.00 s in steps of 0.01
MESSAGE
NEUTRAL IOC1 RESET
DELAY: 0.00
s
Range: 0.00 to 600.00 s in steps of 0.01
MESSAGE
NEUTRAL IOC1 BLOCK:
Off
Range: FlexLogic™ operand
MESSAGE
NEUTRAL IOC1
TARGET: Self-reset
Range: Self-reset, Latched, Disabled
MESSAGE
NEUTRAL IOC1
EVENTS: Disabled
Range: Disabled, Enabled
I
op
3
I_0
K
x
I_1
–
(
)
×
=
where
K
1 16
⁄
=
I
op
0.9375
x
I
injected
=
I
op
3
I
injected
×
=
FLEXLOGIC OPERANDS
NEUTRAL IOC1 FUNCTION:
NEUTRAL IOC1 PICKUP:
NEUTRAL IOC1 SOURCE:
NEUTRAL IOC1 BLOCK:
NEUTRAL IOC1 DPO
NEUTRAL IOC1 OP
NEUTRAL IOC1 PKP
RUN
AND
827035A4.CDR
SETTING
SETTING
Enabled=1
Disabled=0
SETTING
SETTING
I
_0
Off=0
SETTINGS
NEUTRAL IOC1
RESET DELAY :
NEUTRAL IOC1
PICKUP DELAY :
t
PKP
t
RST
3( _0 - K _1 ) PICKUP
I
I
Summary of Contents for UR T60
Page 10: ...x T60 Transformer Protection System GE Multilin TABLE OF CONTENTS ...
Page 14: ...xiv T60 Transformer Protection System GE Multilin 0 1 BATTERY DISPOSAL 0 BATTERY DISPOSAL 0 ...
Page 34: ...1 20 T60 Transformer Protection System GE Multilin 1 5 USING THE RELAY 1 GETTING STARTED 1 ...
Page 436: ...5 298 T60 Transformer Protection System GE Multilin 5 10 TESTING 5 SETTINGS 5 ...
Page 678: ...C 30 T60 Transformer Protection System GE Multilin C 7 LOGICAL NODES APPENDIX C C ...
Page 688: ...D 10 T60 Transformer Protection System GE Multilin D 1 IEC 60870 5 104 PROTOCOL APPENDIX D D ...
Page 700: ...E 12 T60 Transformer Protection System GE Multilin E 2 DNP POINT LISTS APPENDIX E E ...
