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3
= ×
=
+
+
Pol
I
Io
IA IB IC
EQUATION2019-ANSI V1 EN
(Equation 86)
where:
IA, IB and IC are fundamental frequency phasors of three individual phase currents.
The residual current is pre-processed by a discrete fourier filter. Thus the phasor of the
fundamental frequency component of the polarizing current is derived. This phasor is
then multiplied with pre-set equivalent zero-sequence source Impedance in order to
calculate equivalent polarizing voltage VIPol in accordance with the following formula:
(
)
IPol
S
Pol
Pol
V
Zo I
RNPol j XNPOL
I
=
×
=
+ ×
×
EQUATION2013-ANSI V1 EN
(Equation 87)
which will be then used, together with the phasor of the operating current, in order to
determine the direction to the ground fault (Forward/Reverse).
In order to enable current polarizing the magnitude of polarizing current shall be bigger
than a minimum level defined by setting parameter
IPolMin
.
Dual polarizing
When dual polarizing is selected the function will use the vectorial sum of the voltage
based and current based polarizing in accordance with the following formula:
(
)
0
0
0
3
3
s
VTotPol VVPol VIPol
V
Z
IPol
V
RNPol
jXNPol
IPol
=
+
= -
+
×
= -
+
+
×
ANSIEQUATION1878 V1 EN
(Equation 88)
Vpol and Ipol can be either zero sequence component or negative sequence component
depending upon the user selection.
Then the phasor of the total polarizing voltage VTotPol will be used, together with the
phasor of the operating current, to determine the direction of the ground fault (Forward/
Reverse).
7.4.2.3
External polarizing for ground-fault function
The individual steps within the protection can be set as non-directional. When this
setting is selected it is then possible via function binary input BLKx to provide external
directional control (that is, torque control) by for example using one of the following
functions if available in the IED:
1. Distance protection directional function.
2. Negative sequence polarized General current and voltage multi purpose protection
function.
1MRK505222-UUS C
Section 7
Current protection
403
Technical reference manual
Summary of Contents for Relion 670 series
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