ABB RELION 670 Series Technical Manual page 290

Section 7
Impedance protection
Phase selection
"Quadrilateral" zone
IEC09000049 V1 EN-US
Figure 140: Operating characteristic for FRPSPDIS (21) in forward direction for three-phase
The result from rotation of the load characteristic at a fault between two phases is presented in
fig 141. 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" by 2/√3,
from the full
284
W
(
X
Distance measuring zone
fault, ohm/phase domain
RLdFw and RLdRv reach, which is valid at load or three-phase fault.
/ phase )
W
( / phase
R
IEC09000049-1-en.vsd
1MRK 502 066-UUS B
)
Technical manual