GE 750 Instruction Manual page 152

750/760
Feeder Management Relay
RESTRICTED
EARTH FAULT
5–56
• MIN POLARIZING VOLTAGE: This setpoint affects the voltage element only.
As the system zero sequence voltage is used as the polarizing voltage for this
element, a minimum level of voltage must be selected to prevent operation
caused by system unbalanced voltages or VT ratio errors. For well-balanced
systems and 1% accuracy VTs, this setpoint can be as low as 2% of VT nominal
voltage. For systems with high-resistance grounding or floating neutrals, this
setpoint can be as high as 20%. The default value of "0.05 x VT" is appropriate
for most solidly grounded systems.
FIGURE 5–20: Sensitive Ground Directional Logic
e) Restricted Earth Fault
PATH: SETPOINTS S5 PROTECTION
[ ] RESTRICTED EARTH FLT
FUNCTION: Disabled
RESTRICTED EARTH FLT
MESSAGE
RELAYS (3-7): -----
RESTRICTED EARTH FLT
MESSAGE
PICKUP: 0.100 x CT
RESTRICTED EARTH FLT
MESSAGE
DELAY: 0.00 s
Restricted Earth Fault protection is often applied to transformers having grounded
wye windings, to provide sensitive ground fault detection for faults near the
transformer neutral. The Sensitive Ground Input (Terminals G3, H3) can be used.
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SENSTV GND CURRENT RESTRICTED EARTH...
Range: Disabled, Trip, Alarm, Latched
Alarm, Control
Range: Any combination of 3 to 7
Auxiliary relays
Range: 0.005 to 1.000 x CT in steps of
0.001
Range: 0.00 to 600.00 s in steps of 0.01
S5 Protection
GE Multilin