Parameter Value Description
fundamental comp.
This method of measurement suppresses the harmonics or transient voltage
peaks.
Siemens recommends using this setting as the standard method.
RMS value
Select this method of measurement if you want the stage to take harmonics
into account (for example at capacitor banks).
fund. comp. long filter
To implement particularly strong damping of harmonics and transient
faults, select this method of measurement. At 2 periods, the length of the
filter is longer than that of the standard filter.
Note that in this case the pickup time of the stage increases slightly (see
12.18.7 Non-Directional V0 Stage with Zero-Sequence Voltage/Residual
Voltage).
Parameter: Pickup delay
•
Recommended setting value (_:12391:107) Pickup delay = 0 ms
The Pickup delay parameter allows you to delay the analysis of the measurand (to generate the pickup)
depending on the occurrence of the residual voltage. A pickup delay can be necessary if high transients are
anticipated after fault inception due to high line and ground capacitances.
Siemens recommends using the default setting Pickup delay = 0 ms.
Parameter: Threshold
•
Default setting (_:12391:3) Threshold = 30 V
The threshold value of the function is set as the zero-sequence voltage V0. The device calculates the zero-
sequence voltage V0 either from the residual voltage measured via the broken-delta winding or from the
3 phase-to-ground voltages.
The setting value depends on the system grounding:
•
Since virtually the full residual voltage occurs during ground faults in isolated or arc-suppression-coil-
grounded systems, the setting value is uncritical there. Siemens recommends setting the value between
20 V and 40 V. A higher sensitivity (= lower threshold value) can be necessary for high fault resistances.
•
Siemens recommends setting a more sensitive (smaller) value in grounded systems. This value must be
higher than the maximum residual voltage anticipated during operation caused by system unbalances.
EXAMPLE
For an isolated system
The residual voltage is measured via the broken-delta winding:
•
If the ground fault is fully unbalanced, a residual voltage of 100 V is present at the device terminals.
•
The threshold value should be set so that the stage picks up on 50 % of the full residual voltage.
•
At full residual voltage, the zero-sequence voltage is 100 V/√3 = 57.7 V
Setting value: 0.5 ⋅ 57.7 V = 28.9 V ≈ 30 V
Parameter: Dropout ratio
•
Recommended setting value (_:12391:4) Dropout ratio = 0.95
The recommended setting value of 0.95 is appropriate for most applications. To achieve high measurement
precision, the dropout ratio can be reduced to 0.98, for example.
Parameter: Operate delay
•
Default setting (_:12391:6) Operate delay = 3.00 s
The Operate delay allows you to prevent transient residual voltages from initiating a trip. The setting
depends on the specific application.
Protection and Automation Functions
6.15 Sensitive Ground-Fault Detection
610 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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