ABB REL650 series Technical Manual page 146

Section 6
Impedance protection
140
Phase selection
"Quadrilateral" zone
IEC09000049 V1 EN
Figure 59: Operating characteristic for FDPSPDIS (21) in forward direction for
three-phase fault, ohm/phase domain
The result from rotation of the load characteristic at a fault between two phases is
presented in fig 60. Since the load characteristic is based on the same measurement as the
quadrilateral characteristic, it will rotate with the quadrilateral characteristic clockwise by
30 degrees when subject to a pure phase-to-phase fault. At the same time the characteristic
will "shrink", divided by 2/√3, from the full RLdFw and RLdRv reach, which is valid at
load or three-phase fault.
W
( / phase )
X
Distance measuring zone
(
R
IEC09000049-1-en.vsd
1MRK 506 335-UUS A
W
/ phase )
Technical manual