GE B30 UR Series Instruction Manual page 258

5.6 GROUPED ELEMENTS
Two methods of resetting operation are available: "Timed" and "Instantaneous" (refer to the Inverse time overcurrent curve
characteristics section for details on curve setup, trip times and reset operation). When the element is blocked, the time
accumulator will reset according to the reset characteristic. For example, if the element reset characteristic is set to "Instan-
taneous" and the element is blocked, the time accumulator will be cleared immediately.
SETTING
NEUTRAL TOC1
FUNCTION:
Disabled = 0
Enabled = 1
SETTING
NEUTRAL TOC1
SOURCE:
IN
SETTING
NEUTRAL TOC1
BLOCK:
Off = 0
b) NEUTRAL INSTANTANEOUS OVERCURRENT (ANSI 50N, IEC PIOC)

PATH: SETTINGS GROUPED ELEMENTS
 NEUTRAL IOC1
5 
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.
5-136
AND
Figure 5–53: NEUTRAL TIME OVERCURRENT 1 SCHEME LOGIC

SETTING GROUP 1(6)
NEUTRAL IOC1
FUNCTION: Disabled
NEUTRAL IOC1 SIGNAL
MESSAGE
SOURCE: SRC 1
NEUTRAL IOC1
MESSAGE
PICKUP:
NEUTRAL IOC1 PICKUP
MESSAGE
DELAY:
NEUTRAL IOC1 RESET
MESSAGE
DELAY:
NEUTRAL IOC1 BLOCK:
MESSAGE
Off
NEUTRAL IOC1
MESSAGE
TARGET: Self-reset
NEUTRAL IOC1
MESSAGE
EVENTS: Disabled
I 3 × ( I_0 Kx I_1
= –
op
B30 Bus Differential System
SETTINGS
NEUTRAL TOC1
INPUT:
NEUTRAL TOC1
PICKUP:
NEUTRAL TOC1
CURVE:
NEUTRAL TOC1
TD MULTIPLIER:
NEUTRAL TOC 1
RESET:
IN ≥ PICKUP
RUN
t
I

NEUTRAL CURRENT
Range: Disabled, Enabled
Range: SRC 1, SRC 2, SRC 3, SRC 4, SRC 5, SRC 6
Range: 0.000 to 30.000 pu in steps of 0.001
1.000 pu
Range: 0.00 to 600.00 s in steps of 0.01
0.00 s
Range: 0.00 to 600.00 s in steps of 0.01
0.00 s
Range: FlexLogic operand
Range: Self-reset, Latched, Disabled
Range: Disabled, Enabled
) where K 1 16 ⁄
=
5 SETTINGS
FLEXLOGIC OPERANDS
NEUTRAL TOC1 PKP
NEUTRAL TOC1 DPO
NEUTRAL TOC1 OP
827034A3.VSD

NEUTRAL IOC1(6)
(EQ 5.12)
GE Multilin