ABB Relion 670 series - Page 263

jX
R
Load
Load
Load
Load
jX
R
Load
Load
Load
Load
No
operation
en06000403.vsd
IEC06000403 V1 EN
Figure 126: Load encroachment phenomena and shaped load encroachment
characteristic
The Faulty phase identification with load encroachment for mho (FMPSPDIS, 21)
function shapes the characteristic according to the diagram on the right in figure 126. The
load encroachment algorithm will increase the possibility to detect high fault resistances,
especially for phase-to-ground faults at remote line end. For example, for a given setting
of the load angle LdAngle (see figure
127) for the Faulty phase identification with load
encroachment for mho function (FMPSPDIS, 21), the zone reach can be expanded
according to the diagram on the right in figure 126 given higher fault resistance coverage
without risk for unwanted operation due to load encroachment. The part of the load
encroachment sector that comes inside the mho circle will not cause a trip if FMPSPDIS
(21) is activated for the zone measurement. This is valid in both directions.
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 257
Application manual