GE D30 Instruction Manual page 329

CHAPTER 5: SETTINGS
SETTING
NEUTRAL TOC1
FUNCTION:
Enabled = 1
SETTING
NEUTRAL TOC1
SOURCE:
IN
SETTING
NEUTRAL TOC1
BLOCK:
Off = 0
5.7.8.3 Neutral instantaneous overcurrent (ANSI 50N, IEC PIOC)
SETTINGS  GROUPED ELEMENTS  SETTING GROUP 1(6)  NEUTRAL CURRENT  NEUTRAL IOC1(4)
 NEUTRAL IOC1

The neutral instantaneous overcurrent element can 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
phasor 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:
× ; three-phase pure zero-sequence injection:
I = 0.9375 I
op injected
D30 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
Figure 5-107: Neutral time overcurrent 1 logic
SETTINGS
NEUTRAL TOC1
INPUT:
NEUTRAL TOC1
PICKUP:
NEUTRAL TOC1
CURVE:
NEUTRAL TOC1
TD MULTIPLIER:
NEUTRAL TOC 1
RESET:
RUN
AND
IN
t
I
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 K × I_1 ) where K
–
op
FLEXLOGIC OPERANDS
NEUTRAL TOC1 PKP
NEUTRAL TOC1 DPO
PICKUP
NEUTRAL TOC1 OP
Range: Disabled, Enabled
Range: SRC 1, SRC 2
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
GROUPED ELEMENTS
827034A4.VSD
Eq. 5-15
5-197
5