6.3.3.3 Three-phase faults
The operation conditions for three-phase faults are the same as for phase-to-phase
fault, that is equation 29, equation 30 and equation 31 are used to release the operation
of the function.
However, the reach is expanded by a factor 2/√3 (approximately 1.1547) in all
directions. At the same time the characteristic is rotated 30 degrees, counter-clockwise.
The characteristic is shown in figure
104.
0.5·RFltFwdPP·K3
X1·K3
90 deg
0.5·RFltRevPP·K3
30 deg
R (ohm/phase)
X (ohm/phase)
4 X1
3
×
2 RFltFwdPP
3
×
ANSI05000671-4-en.vsd
2
K3
3
=
ANSI05000671 V4 EN
Figure 104: The characteristic of FDPSPDIS (21) for three-phase fault (setting
parameters in italic)
6.3.3.4 Load encroachment
Each of the six measuring loops has its own load encroachment characteristic based on
the corresponding loop impedance. The load encroachment functionality is always
active, but can be switched off by selecting a high setting.
1MRK505222-UUS C Section 6
Impedance protection
225
Technical reference manual
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