Application and Setting Notes
Parameter: V0> threshold value
•
Default setting (_:102) V0> threshold value = 20.000 V
The V0> threshold value parameter allows you to set the zero-sequence (fundamental) voltage sensi-
tivity of the stage. Set the threshold value smaller than the minimum absolute value of the zero-sequence
voltage V0 that must still be detected. Typical values are in the range of 15 V to 25 V.
Parameter: Dir. determination delay
•
Default setting (_:105) Dir. determination delay = 0.00 s
The start of the ground fault normally shows a significant transient behavior. This can lead to an incorrect
direction decision. The direction determination can be delayed from the occurrence of the zero-sequence
voltage with the Dir. determination delay parameter to achieve steady-state measurands. The dura-
tion of the transient cycle is determined from the system conditions and the respective fault characteristics. If
you have no knowledge of a suitable time delay, Siemens recommends keeping the default setting.
Parameter: Forward section +/-
•
Default setting (_:103) Forward section +/- = 80°
With the Forward section +/- parameter, you set the direction characteristic, that is, the forward and
reverse areas.
The Forward section +/- parameter can normally be left at its default setting. With reducing the forward
area, you can provide more security for the direction result, but on the other hand, you increase the proba-
bility of an underfunction.
Parameter: Dir.-result extension
•
Default setting (_:110) Dir.-result extension = 5.00 s
With the Dir.-result extension parameter, you define the time for extending the last determined direc-
tion result if the conditions for further direction determination are no longer met.
This timer can be used to generate a stable direction indication under fluctuating zero-sequence harmonics. A
stable direction indication again can be required for the implementation of a prioritization schema between
different parallel working detection methods (stages).
Parameter: Harmonic selection
•
Default setting (_:201) Harmonic selection = 5th harmonic
With the Harmonic selection parameter, you select to use the 3rd, 5th, or 7th harmonic phasor of the
zero-sequence voltage V0 and of the zero-sequence current 3I0 for direction determination.
Parameter: Min. 3I0> harmonic
•
Default setting (_:203) Min. 3I0> harmonic = 0.030 A
With the Min. 3I0> harmonic parameter, you define the threshold value of the zero-sequence harmonic
current 3I0harm. for detecting the ground fault and for starting direction determination. You can find more
information in the section Ground-Fault Detection, Pickup, Page 602.
This parameter needs to be set according to the experience from the specific network. This requires the anal-
ysis of permanent ground faults from the network. If such information is unavailable, Siemens recommends a
rather low setting in the area of 5 mA to 10 mA secondary.
Parameter: 3I0 harm. dropout ratio
•
Default setting (_:204) 3I0 harm. dropout ratio = 0.60
6.15.9.2
Protection and Automation Functions
6.15 Sensitive Ground-Fault Detection
SIPROTEC 5, Overcurrent Protection, Manual 605
C53000-G5040-C017-8, Edition 07.2017
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