Siemens siprotec SJ62 User Manual page 217

2 Functions
Ungrounded
System
215
when directional determination drops out, and the message is held for this period of
time.
When address 3124 PHI CORRECTION is set to 0.0°, then the setting in address
3125 signifies the following:
• MEAS. METHOD = COS ϕ
the resistive component of the ground current with respect to the displacement
voltage is most relevant for the current value RELEASE DIRECT. (3I0dir)
MEAS. METHOD = SIN ϕ
the reactive (capacitive) component of the ground current with respect to the dis-
placement voltage is most relevant for the current value RELEASE DIRECT.
(3I0dir) (see Figure 2-78).
Figure 2-78 Directional characteristic for sin–ϕ–measurement
• In address 3124 PHI CORRECTION the directional line, in this respect, may be
rotated within the range ± 45°. Figure "Directional characteristic for cos-ϕ-measure-
ment" in the functional description of the sensitive ground fault detection gives an
example regarding this topic.
In an ungrounded system with a ground fault on a cable, capacitive ground currents of
the galvanically connected system flow via the measuring point, apart from the ground
current generated on the faulty line, which flows directly via the fault location (i.e. not
via the measuring point). A setting equal to about half of this ground current is to be
selected. The measurement type should be SIN ϕ, since capacitive ground current is
most relevant here.
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015