ABB RELION REX640 Technical Manual page 535

1MRS759142 C
REX640
Technical Manual
Y is calculated. This phasor is used as directional phasor in determining the
osum CPS _
direction of the fault.
Y t Y t
( ) ( )
osum CPS = osum
_
1 1
GUID-EF3163AC-C589-46BD-A45C-79D17FD3B8C4 V1 EN
Y ( ) t Y ( ) t
osum CPS _ = osum +
2 1
GUID-8E66FD4E-0FAB-4F0C-A38B-0E6FF1070648 V1 EN
Y t Y t
( ) ( )
osum CPS _ = osum +
3 1
GUID-DA64391A-DAE9-444A-B002-5E631735CED3 V1 EN
Y ( ) t Y ( ) t
osum CPS _ = osum +
4 1
GUID-CD976074-C6B7-4BCC-8D6F-2E5836AF3104 V1 EN
Y t Y t
( ) ( )
osum CPS _ = osum +
5 1
GUID-CE2885A6-00CD-4DDE-A6BD-C550F25B9717 V1 EN
GUID-5C356126-83C7-492D-839C-F06BF7AB7FF0 V1 EN
Figure 288: Principle of Cumulative Phasor Summing (CPS)
The CPS technique provides a stable directional phasor quantity despite individual
phasors varying in magnitude and phase angle in time due to an unstable fault type
such as a restriking or intermittent earth fault. This is also true for harmonic
components included in the sum admittance phasor. Harmonics typically have a
highly fluctuating character.
Harmonic components provide a more distinctive directional determination in
compensated networks than the fundamental frequency component. With higher
frequencies, the compensation coil appears as very high impedance and the harmonics
are not affected by compensation coil and degree of compensation. When harmonics
are present, they cause the sum admittance phasor to behave as in case of an unearthed
network, where directional phasors point in opposite directions in the faulty and
healthy feeder.
Y ( ) t
osum
2
Y t Y t
( ) ( )
osum + osum
2 3
Y ( ) t Y ( ) t Y
osum + osum + osum
2 3
Y t Y t Y
( ) ( )
osum + osum + osum
2 3
Section 4
Protection functions
(Equation 79)
(Equation 80)
(Equation 81)
( ) t
4
(Equation 82)
t Y t ( )
( )
+ osu m m
4 5
(Equation 83)
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