ABB RELION Series Technical Manual page 384

Section 4
Protection functions
378
Y ( ) t Y ( ) t
=
osum CPS _ osum
5 1
GUID-8E0FAAAB-F656-4FCF-AC71-42C357E77F3E V1 EN
GUID-69E030E7-F3CF-4872-AF6A-3D12002EA3AC V1 EN
Figure 197: 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 a non-stable fault type
such as restriking or intermittent earth fault. This is also true for harmonic components
included in the sum admittance phasor. Harmonics have typically a highly fluctuating
character.
Harmonic components provide a more distinctive directional determination in
compensated networks than the fundamental frequency component. The higher the
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 fully opposite directions in the faulty and
healthy feeder.
The direction of the MFADPSDE function is defined with setting Directional mode as
"Forward" or "Reverse". The operation characteristic is defined by tilted operation
sector as illustrated in Figure
that is, it is valid both in compensated and unearthed networks, also if the
compensation coil is temporarily switched off. The tilt of the operation sector is
defined with setting Tilt angle to compensate the measurement errors of residual
current and voltage transformers. The typical setting value of 5 degrees is
recommended, but it should always reflect the actual maximum expected
measurement errors.
In case of unearthed network operation, adequate tilt angle must be
allowed to ensure dependable operation of MFADPSDE.
Y ( ) t Y ( ) t
+ + +
osum osum
2 3
198. The characteristic provides universal applicability,
1MRS758755 A
Y ( ) t Y t ( )
+
osum osu m m
4 5
(Equation 39)
REC615 and RER615
Technical Manual