Functions
2.11 Ground Fault Protection 64, 67N(s), 50N(s), 51N(s)
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A4, Release date 08.2010
194
If direction determination is used in conjunction with one of the current elements discussed above (50Ns-1
PICKUP, addresses 3117 ff, or 51Ns PICKUP, addresses 3119 ff), it is sensible to select a value for address
RELEASE DIRECT. that is lower than or equal to the above pickup value.
A corresponding message (reverse, forward, or undefined) is issued upon direction determination. To avoid
chatter for this message resulting from extremely varying ground connection currents, a dropout delay RESET
DELAY, entered at address 3126, is initiated 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°, in address 3125 the following signifies
• 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. (3I0 DIR.),
MEAS. METHOD = SIN ϕ
the reactive (capacitive) component of the ground current with respect to the displacement voltage is most
relevant for the current value RELEASE DIRECT. (3I0 DIR.) (Figure 2-71).
Figure 2-71 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 2-59 "Directional characteristic for cos-ϕ-measurement" in the functional description of the sen-
sitive ground fault detection gives an example regarding this topic.
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