Three-Phase Faults; Load Encroachment - ABB Relion 670 Series Technical Reference Manual

1MRK505222-UUS C
6.3.3.3
6.3.3.4
Technical reference manual

Three-phase faults

The operation conditions for three-phase faults are the same as for phase-to-phase
fault, that is equation 29, equation
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.
×
4 X1
3
0.5·RFltFwdPP·K3
X1·K3
0.5·RFltRevPP·K3
2
=
K3
3
ANSI05000671 V4 EN
Figure 104: The characteristic of FDPSPDIS (21) for three-phase fault (setting
parameters in italic)

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.
30 and equation
X (ohm/phase)
90 deg
2 RFltFwdPP
30 deg
ANSI05000671-4-en.vsd
Section 6
Impedance protection
31 are used to release the operation
×
3
R (ohm/phase)
225