ABB RELION Series, Technical Manual

Page: 383 / 804

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 below.
Y Y j Y Y G j B
osum
n
n
o osum
=




+ ⋅ +





 =
+ ⋅
=
∑
Re Im
0
1
0
1
0
2
9
1
GUID-6660AD60-0694-4808-8146-A1F053DA5F7C V1 EN
(Equation 34)
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
Y
osum
obtained from the Multi-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 Figure 197 . It is the result of adding values of the
measured sum admittance phasors together in phasor format in chronological order
during the fault. Using the discrete sum admittance phasors
Y
osum
in different time
instants (t
1
...t
5
), the corresponding accumulated sum admittance phasor
Y
osum CPS _
is
calculated. This phasor is used as directional phasor in determining the direction of the
fault.
Y t Y t
osum CPS osum _
( ) ( )
1 1
=
GUID-EDC80710-FA5D-4966-AE81-888E8B4D2CD5 V1 EN
(Equation 35)
Y t Y t Y t
osum CPS osum osum _
( ) ( ) ( )
2 1 2
= +
GUID-696EFC44-7AF4-45A9-A3F4-11C153143D55 V1 EN
(Equation 36)
Y t Y t Y t Y t
osum CPS osum osum osum _
( ) ( ) ( ) ( )
3 1 2 3
= + +
GUID-A18538B4-EFCD-4844-AEFB-0BB92358582A V1 EN
(Equation 37)
Y t Y t Y t Y t Y t
osum CPS osum osum osum osum _
( ) ( ) ( ) ( ) ( )
4 1 2 3 4
= + + +
GUID-EBDE2421-0F49-4141-87E2-433DF64503C9 V1 EN
(Equation 38)
1MRS758755 A
Section 4
Protection functions
REC615 and RER615 377
Technical Manual