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Functions
2.3 Directional Overcurrent Protection Ground 67, 67N
Direction Determination via Ground Element using Negative Sequence Values
Figure 2-25 shows how the reference voltage for the directional ground element is processed using the nega-
tive sequence values based on a single-phase ground fault in phase A. The negative sequence voltage is used
as reference voltage; the negative sequence current is used as current for direction determination in which the
fault current is represented. The fault current -3I
by fault angle ϕ
voltage 3V
2
In this case, a rotation by -45°.
Figure 2-25
The forward area is a range of ±86° around the rotated reference voltage V
sequence current -3I
2.3.9
Setting Notes
General
When selecting the directional ground overcurrent protection in DIGSI, a dialog box opens with several tabs for
setting the associated parameters. Depending on the functional scope specified during configuration of the pro-
tective functions in address 116 67N/67N-TOC, the number of tabs can vary.
When selecting 67N/67N-TOC = Definite Time, only the settings for the definite time elements are avail-
able. Selecting TOC IEC or TOC ANSI the inverse time characteristics will be available too. The superimposed
directional elements 67N-2 and 67N-1 apply in all these cases.
The directional ground current element can be turned ON or OFF at address 1601 FCT 67N/67N-TOC.
Depending on the parameter 613 Gnd O/Cprot. w., the device can operate using either measured values
IN or the quantities 3I0 calculated from the three phase currents. Devices featuring a sensitive ground current
input generally use the calculated quantity 3I0.
The directional orientation of the function is influenced by parameter 201 CT Starpoint (see Chapter 2.1.3).
96
. The reference voltage is rotated by the setting value 1619 ROTATION ANGLE.
sc
Rotation of the reference voltage, directional ground element with negative sequence values
is in this area, the device detects forward direction.
2
is phase opposite to the fault current I
2
E50417-G1140-C344-A5, Release date 11.2012
and follows the
scA
If the vector of the negative
ref,rot
SIPROTEC, 7SK80, Manual
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