ABB RELION REX640 Technical Manual page 559

1MRS759142 F
n
U
0
n
B
o
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
Y
osum
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
frequency 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
Y
osum CPS
direction of the fault.
Y
osum CPS
Y
osum CPS
Y
osum CPS
REX640
Technical Manual
nth harmonic frequency zero-sequence voltage phasor
nth harmonic frequency susceptance,

 
= + ⋅
1
Re Y j Im Y

 
0

The polarity of the polarizing quantity (residual voltage) can be changed
(rotated by 180 degrees) by setting the
or by switching the polarity of the residual voltage measurement wires.
...t ), the corresponding accumulated sum admittance phasor
1 5
_
is calculated. This phasor is used as directional phasor in determining the
( ) t Y ( ) t
=
_ osum
1 1
( ) t Y ( ) t Y
= +
_ osum
2 1
( ) t Y ( ) t Y
= +
_ osum
3 1
Im Y

9
∑
+  = + ⋅
1 n 1
Y G j B
0 0 o

=
n 2
Figure 321
. It is the result of adding the values of
( ) t
osum
2
( ) t Y ( ) t
+
osum osum
2 3
Protection functions
( )
n
0
osum
Pol reversal parameter to "True"
Y
obtained from the Multi-
osum
Y
osum
(Equation 90)
in different
(Equation 91)
(Equation 92)
(Equation 93)
559