Functions
2.13 Dir. Intermittent earth fault protection
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A5, Release date 11.2012
215
Logic
The following figure shows the logic diagram of the directional intermittent ground fault protection function.
Figure 2-78 Logic diagram of the directional intermittent ground fault protection
Direction Determination
The ground fault is detected by evaluating the fundamental component of the displacement voltage. The sen-
sitivity is determined using the settable threshold value Vgnd> / 3V0>. Direction determination is started after
the ground fault has been detected. For this purpose, the igniting current pulses are extracted from the ground
current signal. The igniting current pulse and the associated maximum displacement voltage over time are
compared with regard to their phase relationship. The fault direction forward or reverse is derived from this
comparison. Each detected ignition pulse receives a direction information. If no clear direction determination is
possible, the direction information pertaining to the pulse is undefined. The direction results of the recurring
ignition pulses are counted and are available as value indication if their value is different than zero.
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