ABB REF615 L User Manual

s1s2
s1
s2
VDR
Stabilizing
Resistor
High impedance
protection
(HREFPDIF)
GUID-367BDBC9-D2E8-48D3-B98F-623F7CD70D99 V3 EN
Figure 233: Connection scheme for the restricted earth-fault protection
according to the high-impedance principle
High-impedance principle
High-impedance principle is stable for all types of faults outside the zone of
protection. The stabilization is obtained by a stabilizing resistor in the differential
circuit. This method requires that all the CTs used have a similar magnetizing
characteristic, same ratio and relatively high knee point voltage. CTs on each sides
are connected in parallel along with a relay-measuring branch as shown in
Figure
234. The measuring branch is a series connection of stabilizing resistor and IED.
Section 4 1YHT530004D05 D
Protection functions
434 615 series
Technical Manual

ABB REF615 L Specifications

General

Type	Feeder Protection Relay
Rated Frequency	50/60 Hz
Weight	Approx. 1.5 kg
Communication Protocols	IEC 61850, Modbus RTU, DNP3
Protection Functions	Overcurrent, Earth fault, Thermal overload, Under/Over voltage, Under/Over frequency
Enclosure	IP20