Switch On To Fault (Sotf) - GE Multilin 850 Instruction Manual
Feeder protection system
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PROTECTION
Switch on to Fault
(SOTF)
NOTE:
FASTPATH:
4–164
Switch on to Fault protection (SOTF) is provided for high speed clearance of any detected
fault immediately following manual closure or closure after a long open time of the circuit
breaker. Without SOTF, there is a risk that if the breaker is closed onto close-in three-phase
fault, the measured voltages may be too small for the impedance zones or the directional
overcurrent stages to operate reliably.
SOTF 1 (2 or 3) are associated with Breaker 1. The SOTF logic uses breaker status from
BKR1. SOTF 4 (5 or 6) are associated with Breaker 2. The SOTF logic uses breaker status
from BKR2. The CT Input and VT Input settings should be configured to match their
respective breakers.
Path:
Setpoints > Protection > Group 1(6) > Current > SOTF 1(X)
FUNCTION
Range: Disabled, Trip, Alarm, Latched Alarm, Configurable
Default: Disabled
VT INPUT
Range: Ph VT Bnk1-J2
Default: Ph VT Bnk1-J2
CT INPUT
Range: CT Bank 1-J1
Default: CT Bank 1 -J1
DEAD LINE MAX VOLTAGE
Range: 0.05 to 1.00 x VT in steps of 0.01
Default: 0.20 x VT
This setting sets the dead line voltage threshold. Voltage above this setting is not
considered for the dead line condition. To be in a dead line condition all phases must be
below this threshold.
DEAD LINE MAX CURRENT
Range: 0.05 to 1.00 x CT in steps of 0.01
Default: 0.05 x CT
This setting allows the user to define the dead line current threshold. Currents above this
setting value are not considered to be in dead line condition. To be in dead line condition
all phases have to be below this threshold.
DEAD LINE PICKUP DELAY
Range: 0.000 to 6000.000 s in steps of 0.001
Default: 10.000 s
This setting allows the user to define the dead line pickup delay. Once in dead line
condition for current AND voltage, the dead line signal will be set after this delay if
conditions are still true. This value should be longer than the longest autoreclose shot
time.
SOTF MAX VOLTAGE
Range: 0.05 to 3.00 x VT in steps of 0.01
Default: 0.50 x VT
This setting allows the user to define the SOTF maximum voltage threshold. Above this
setting the element is not in SOTF condition. To be in SOTF condition, the same phase for
current and voltage have to be in SOTF condition.
VTs should be connected to the line side and not the bus side for detection by voltage and
currents.
850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS
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