External Polarizing For Earth-Fault Function - ABB REG650 Technical Manual

1MRK 502 048-UEN A
8.2.7.3
Technical manual
×
2
I2 = (IL1+alpha IL2+alpha IL3)/3
IECEQUATION2406 V1 EN
where:
IL1, IL2 and IL3 are fundamental frequency phasors of three individual phase currents.
alpha phasor with an angle of 120 degrees.
The polarizing 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:
= × = + ×
UIPol Z IPol (RNPol
0s
EQUATION1877 V2 EN
which will be then used, together with the phasor of the operating directional 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:
+
UTotPol=UUPol UIPol=UPol
IECEQUATION2408 V1 EN
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).

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(where x
indicates the relevant step within the protection) 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 based overcurrent function.
×
×
j XNPol) IPol
(
+ × = +
Z IPol UPol RNPol
0s
Section 8
Current protection
(Equation 52)
(Equation 53)
)
+ ×
jXNPol Ipol
(Equation 54)
195