GE Multilin 750/760 Feeder Management Relay 5-55
5 SETPOINTS 5.6 S5 PROTECTION
5
Figure 5–20: SENSITIVE GROUND DIRECTIONAL LOGIC
e) RESTRICTED EARTH FAULT
PATH: SETPOINTS ÖØ S5 PROTECTION ÖØ SENSTV GND CURRENT ÖØ RESTRICTED EF
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.
Although the 750/760 is designed for feeder protection, it can provide Restricted Earth Fault protection on transformers that
do not have dedicated protection. To use the 750/760 for this type of protection, a stabilizing resistor and possibly a non-lin-
ear resistor will be required.
The inclusion of a stabilizing resistor encourages the circulating fault current to flow via the magnetizing impedance of the
saturated current transformer thus minimizing spill current in the REF relay. A non-linear resistor will be required where the
voltage across the inputs would be greater than 2000 V. Refer to Restricted Earth Fault Inputs on page 3–10 for the con-
nections required to use the 750/760 to perform Restricted Earth Fault protection.
îš„ RESTRICTED EF
îš„ [ENTER] for more
RESTRICTED EARTH FLT
FUNCTION: Disabled
Range: Disabled, Trip, Trip & AR, Alarm, Latched Alarm,
Control
RESTRICTED EARTH FLT
RELAYS (3-7): -----
Range: Any combination of 3 to 7 Auxiliary relays
RESTRICTED EARTH FLT
PICKUP: 0.100 x CT
Range: 0.005 to 1.000 x CT in steps of 0.001
RESTRICTED EARTH FLT
DELAY: 0.00 s
Range: 0.00 to 600.00 s in steps of 0.01
ENTER
ESCAPE
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Courtesy of NationalSwitchgear.com
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