to the displacement voltage V
0
and compared with setting value RELEASE DIRECT.. The example is there-
fore suitable for ground fault direction in resonant grounded systems where quantity 3Ι0 · cos ϕ is relevant.
The directional limit lines are perpendicular to axis 3Ι0
real
.
[7sj6-richtungskennlinie-bei-cos-messung-101210, 1, en_US]
Figure 2-68 Directional characteristic for cos–ϕ–measurement
The directional limit lines may be rotated by a correction angle (address PHI CORRECTION) up to ± 45°.
Therefore, in grounded systems it is possible e.g. to increase sensitivity in the resistive-inductive range with a
rotation of –45°, or in case of electric machines connected to the busbar of an ungrounded power system in
the resistive- capacitive range with a rotation of +45° (see the following Figure). Furthermore the directional
limit lines may be rotated by 90° to determine ground faults and their direction in isolated systems.
Functions
2.12 Ground Fault Protection 64, 67N(s), 50N(s), 51N(s)
174 SIPROTEC 4, 7SJ80, Manual
E50417-G1140-C343-A8, Edition 12.2017
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