ABB REG670 Applications Manual page 237

1MRK 502 071-UEN -
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
different protection functions, which have their operation based on properties of
measured voltage and current phasors.
Voltage inversion
Figure 110 presents a part of series compensated line with reactance X
IED point and the fault in point F of series compensated line. The voltage
measurement is supposed to be on the bus side, so that series capacitor appears
between the IED point and fault on the protected line. Figure
corresponding phasor diagrams for the cases with bypassed and fully inserted series
capacitor.
Voltage distribution on faulty lossless serial compensated line from fault point F to the
bus is linearly dependent on distance from the bus, if there is no capacitor included in
scheme (as shown in figure 111). Voltage U
drop D U
on the faulty line and lags the current I
L
The situation changes with series capacitor included in circuit between the IED point
and the fault position. The fault current I
capacitor, generally decreases total impedance between the sources and the fault. The
reactive voltage drop D U
Voltage drop DU
on series capacitor lags the fault current by 90 degrees. Note that
C
line impedance X could be divided into two parts: one between the IED point and
L1
the capacitor and one between the capacitor and the fault position. The resulting
voltage U in IED point is this way proportional to sum of voltage drops on partial
M
impedances between the IED point and the fault position F, as presented by
( )
= × -
U I j X X
M F L 1 C
EQUATION1901 V1 EN
With bypassed
Source voltage
Source
X
S
~
I
F
IEC06000605 V1 EN
Figure 110: Voltage inversion on series compensated line
measured at the bus is equal to voltage
M
(see figure 111) is increased due to the series
F
on X line impedance leads the current by 90 degrees.
L L1
With inserted
capacitor capacitor
U'
M
U
M
U
X
L1
F
X
C
Z<
Section 8
Impedance protection
between the
L1
111 presents the
by 90 electrical degrees.
F
(Equation 108)
Pre -fault voltage
Fault voltage
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