To carry out the direction determination, the following condition must also be met in addition to the
preceding 2 conditions:
The zero-sequence harmonic voltage V0harm. must exceed the threshold which is 0.02 % of the secondary
rated voltage of the voltage transformer. If this condition is not met, the direction result is unknown.
The direction result is indicated via the
Ground fault
signal.
The stage pickup depends on the direction result and on the Directional mode parameter:
•
If the Directional mode parameter is set as forward or reverse, the stage picks up when the direc-
tion result equals the parameterized direction, and the
Pickup
is signaled with the determined direction.
•
If the Directional mode parameter is set as non-directional, the stage picks up regardless of the
direction result, and the
Pickup
is signaled with the unknown information.
Direction Determination
With the Harmonic selection parameter, you can select the 3rd, 5th, or 7th harmonic phasor for direction
determination. The direction is determined via the calculation of the phase angle between the following
values:
•
Zero-sequence harmonic current 3I0harm.
•
Rotated zero-sequence harmonic voltage V0harm., indicated in the following as reference voltage V
ref,rot
The reference voltage is rotated by the angle +90° in relation to V0. This provides the maximum security for
the direction determination assuming that 3I0harm. is a reactive current.
The rotated reference voltage V
ref,rot
and the Forward section +/- parameter define the forward and
reverse area. For details, refer to Figure 6-142.
The areas in the following figure are as follows:
•
The forward area results as range ± Δφ around the rotated reference voltage V
ref,rot
. You can set the value
± Δφ with the Forward section +/- parameter. If the vector of the secondary ground current
-3I0harm. lies within this area, the direction result is forward.
•
The mirror area of the forward area is the reverse area. If the vector of the secondary ground current
-3I0harm. lies within this area, the direction result is reverse.
•
In the intermediate range, the direction is unknown.
[dw_sensGFP V0 dir harmonic, 1, en_US]
Figure 6-142 Direction Characteristic
Protection and Automation Functions
6.15 Sensitive Ground-Fault Detection
SIPROTEC 5, Overcurrent Protection, Manual 603
C53000-G5040-C017-8, Edition 07.2017
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