Voltage And Current Inversion - ABB RELION 670 SERIES Applications Manual

1MRK 506 369-UUS -
8.13.3.3
Line distance protection REL670 2.2 ANSI
Application manual

Voltage and current inversion

Series capacitors influence the magnitude and the direction of fault currents in series
compensated networks. They consequently influence phase angles of voltages measured
in different points of series compensated networks and this performances of different
protection functions, which have their operation based on properties of measured voltage
and current phasors.
Voltage inversion
Figure 81 presents a part of series compensated line with reactance X
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
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 82). Voltage V
the faulty line and lags the current I
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 V
drop DV
on series capacitor lags the fault current by 90 degrees. Note that line impedance
C
X could be divided into two parts: one between the IED point and the capacitor and one
L1
between the capacitor and the fault position. The resulting voltage V
way proportional to sum of voltage drops on partial impedances between the IED point
and the fault position F, as presented by
( )
= × -
V I j X X
M F L1 C
EQUATION1995-ANSI V1 EN
82 presents the corresponding phasor diagrams for the
measured at the bus is equal to voltage drop D V
M
by 90 electrical degrees.
F
(see figure 82) is increased due to the series
F
on X line impedance leads the current by 90 degrees. Voltage
L L1
Section 8
Impedance protection
between the IED
L1
in IED point is this
M
(Equation 362)
on
L
403