GE 850 - Page 464

7–44 850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
TRANSIENT GROUND FAULT DETECTION CHAPTER 7: MONITORING
Figure 7-25: Transient Ground Fault Detection logic diagram
Measured: I
N
Measured: V
N
SETPOINT
Frequency : 50 or 60
BandPass Filter 220/264 Hz
Average Transient Q Average Transient P
Calculate dynamic threshold Q, max average Q and evaluate Positive/Negative Q Calculate dynamic threshold P, max average P and evaluate Positive/Negative P
SETPOINT
Power Threshold
Directional Logic
SETPOINT
Residual Voltage Pickup
Activate TGFD RMS V
N
> Threshold
Select Power P or Q
SETPOINT
BLOCK: Off = 0
AND
SETPOINT
Function: Disabled
Latched Alarm Alarm
OR
LED: ALARM
RESET
Command
S R
LATCH
TGFD Forward
FlexLogic Operands
TGFD Reverse
FlexLogic Operands
AND AND
OR
TGFD Start
FlexLogic Operands
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