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 UIPol in accordance with the following
formula:
0s
UIPol Z
IPol (RNPol j XNPol) IPol
=
×
=
+ ×
×
EQUATION1877 V2 EN
(Equation 66)
which will be then used, together with the phasor of the operating current, in order to
determine the direction to the earth 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
s
UTotPol=UUPol UIPol=UPol Z
IPol UPol
RNPol
jXNPol Ipol
+
+
×
=
+
+
×
IECEQUATION2408 V1 EN
(Equation 67)
UPol 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 UTotPol will be used, together with the
phasor of the operating current, to determine the direction of the earth fault (Forward/
Reverse).
8.4.7.3
External polarizing for earth-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 BLKSTx 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.
8.4.7.4
Directional detection for earth fault function
Zero sequence components will be used for detecting directionality for earth fault
function. In some cases zero sequence quantities might detect directionality wrong.
Negative sequence quantities will be used in such scenario. The user can select either
zero sequence components or negative sequence components for detecting
directionality with the parameter
SeqTypeIPol
. I3PDIR input always connected to the
same source as I3P input.
Section 8
1MRK502052-UEN B
Current protection
364
Technical manual
Содержание Relion REG670
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