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