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
To Next Page
Loading...
