ABB RELION 670 Series Technical Manual page 286

Section 7
Impedance protection
<
3 0 I 3 0
EQUATION1815-ANSI V1 EN-US
where:
3I0Enable_PG is the minimum operation current for forward ground measuring loops,
3I0BLK_PP
Iphmax
7.7.6.3 Three-phase faults
The operation conditions for three-phase faults are the same as for phase-to-phase fault, that is
equation 79, equation
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 136.
K3 = 2 / sqrt(3)
IEC09000635 V2 EN-US
Figure 136: The characteristic of FRPSPDIS (21) for three-phase fault (set angle 70°)
280
I BLK _ PP
is 3I limit for blocking phase-to-phase measuring loop and
0
is maximal magnitude of the phase currents.
80 and equation
×
4 X1PP
3
X1·K3 30 deg
0.5·RFRvPP·K3
81 are used to release the operation of the function.
X (ohm/phase)
0.5·RFFwPP·K3
1MRK 502 066-UUS B
GUID-0CB276AE-1700-4ACB-8F90-E8E1FD670365 v1
2
RFwPP ×
3
R (ohm/phase)
30 deg
IEC09000635-1-en.vsd
Technical manual
(Equation 81)