ABB RELION REX640 Technical Manual page 534

Section 4
Protection functions
528
n
3 I
 
⋅
n
0
Im Y Im j B
 
= = ⋅
 
0
n
 
U
−
 
 0 
GUID-6DC260CF-024F-4043-A594-9218A3BCB221 V1 EN
n 2, 3, 5, 7 and 9
nth harmonic frequency neutral admittance phasor
n
Y
0
nth harmonic frequency zero-sequence current phasor
n
I
0
nth harmonic frequency zero-sequence voltage phasor
n
U
0
nth harmonic frequency susceptance,
n
B
o
n
Im Y
( )
0
For fault direction determination, the fundamental frequency admittance and
harmonic susceptances are summed together in phasor format. The result is the sum
admittance phasor defined as

1
Y Re Y j Im
 
osum = + ⋅
0

 

GUID-F4EFA0CB-B548-4771-B205-AFAB90E20FE2 V1 EN
The polarity of the polarizing quantity (residual voltage) can be
changed (rotated by 180 degrees) by setting the Pol reversal
parameter to "True" or by switching the polarity of the residual
voltage measurement wires.
Fault direction determination
If an earth fault is detected by the GFC module, the fault direction is evaluated based
on the calculated sum admittance phasor
admittance calculation module. To obtain dependable and secure fault direction
determination regardless of the fault type (transient, intermittent, restriking,
permanent, high or low ohmic), the fault direction is calculated using a special
filtering algorithm, Cumulative Phasor Summing (CPS) technique. This filtering
method is advantageous during transient, intermittent and restriking earth faults with
dominantly non-sinusoidal or transient content. It is equally valid during continuous
(stable) earth faults.
The concept of CPS is illustrated in
the measured sum admittance phasors together in phasor format in chronological
order during the fault. Using the discrete sum admittance phasors
time instants (t ...t ), the corresponding accumulated sum admittance phasor
1 5
n
o
9

1 n 1
Y Y G j B
+  = + ⋅
∑
0 0 o osum
n 2

=
Y
osum
Figure 288. It is the result of adding the values of
1MRS759142 C
obtained from the Multi-frequency
Y
osum
Technical Manual
(Equation 77)
(Equation 78)
in different
REX640