6–68 350 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
S3 PROTECTION CHAPTER 6: SETPOINTS
Ground/Sensitive
Ground timed
overcurrent
protection
The relay has one Ground Time Overcurrent protection per setpoint group. The settings of
this function are applied to the ground input current to produce trip or pickup flags. The
Ground TOC pickup flag is asserted, when the ground current is above the PKP value. The
Ground TOC operate 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 to operate is reached. The selection of Definite Time has a base time
delay of 0.1 s, multiplied by the selected TD multiplier. For example the operating time for
TOC set to Definite Time and a TDM set to 5 will result in 5*0.1 = 0.5 s.
The following path is available using the keypad. For instructions on how to use the
keypad, please refer to Chapter 3 - Working with the Keypad.
PATH:
SETPOINTS > S3 PROTECTION > SETPOINT GROUP 1(2) > GROUND TOC
NOTE:
The settings from the menu for Sensitive Ground TOC, appears only upon selection of the
Sensitive Ground CT when ordering the relay. Otherwise, the relay displays the menu for
Ground TOC protection.
GND TOC FUNCTION
Range: Disabled, Trip, Alarm, Latched Alarm
Default: Disabled
The selection of the Latched Alarm, Alarm, or Trip setting enables the Ground/Sensitive
Ground TOC function. The output relay #1 “Trip” will operate, if the Ground/Sensitive
Ground TOC function is selected as Trip, and the measured ground current satisfies the
operating condition set by the settings. The “ALARM” LED will not turn on if the TOC
operates when set to the Trip function. The “ALARM” LED will flash upon phase TOC
operation, with the TOC function selected as Alarm, and will self-reset, when this
operation clears. If Latched Alarm is selected as the TOC function, the “ALARM” LED will
flash during TOC operation, and will stay “ON” after the condition clears, until the reset
command is initiated. The output relay #1 “Trip” will not operate if the Latched Alarm or
Alarm function is selected. Any or all of output relays 3 to 6 can be selected to operate
when the Ground TOC function is selected as Latched Alarm, Alarm, or Trip.
GND TOC PKP
Range: 0.04 to 20.00 x CT in steps of 0.01 x CT
Default: 1.00 x CT
SENS.GND TOC PKP
Range: 0.005 to 3.00 x CT in steps of 0.001 x CT
Default: 1.00 x CT
This setting sets the time overcurrent pickup level. For example, a PKP setting of 0.9 x CT
with 300:5 CT translates into 270A primary current.
GND TOC CURVE
Range: ANSI Extremely/Very/Moderately/Normally Inverse, Definite Time, IEC Curve A/B/C
and Short Inverse, IAC Extremely/Very/Inverse/Short, User Curve, FlexCurve A, FlexCurve B
Default: Extremely Inverse
This setting sets the shape of the selected over-current inverse curve. If none of the
standard curve shapes is appropriate, a custom User curve, or FlexCurve can be
created. Refer to the User curve and the FlexCurve setup for more detail on their
configurations and usage.
Courtesy of NationalSwitchgear.com
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