Neutral Time Overcurrent Protection - GE 845 Instruction Manual

PROTECTION
Neutral Time
Overcurrent
Protection
4–170
The 845 computes the neutral current (In) using the following formula:
|In|=|Ia+Ib+Ic|
The settings of this function are applied to the neutral current to produce Trip or Pickup
flags. The Neutral TOC Pickup flag is asserted when the neutral current is above the PKP
value. The Neutral TOC Trip flag is asserted if the element stays picked up for the time
defined by the selected inverse curve and the magnitude of the current. The element
drops from Pickup without operation if the measured current drops below 97 to 98% of the
Pickup value before the time for operation is reached. When Definite Time is selected, the
time for Neutral TOC operation is defined only by the TDM setting.
Path:
Setpoints > Protection > Group 1(6) > Current > Neutral TOC 1
FUNCTION
Range: Disabled, Trip, Alarm, Latched Alarm, Configurable
Default: Disabled
INPUT
Range: Phasor, RMS
Default: Phasor
PICKUP
Range: 0.050 to 30.000 x CT in steps of 0.001 x CT
Default: 1.000 x CT
CURVE
Range: IEEE Extremely/Very/Moderately Inverse
ANSI Extremely/Very/Normally/Moderately Inverse
Definite time
IEC A/B/C and Short Inverse
IAC Extremely/Very/Inverse/Short Inverse
FlexCurve A/B/C/D, I2t, I4t
Default: IEEE Moderately Inverse
TDM
Range: 0.05 to 600.00 in steps of 0.01
Default: 1.00
RESET
Range: Instantaneous, Timed
Default: Instantaneous
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS