ABB REL670 2.2 IEC - Page 180

line parameters during fault conditions. We study the basic performances for the
same network with and without series capacitor. Possible effects of spark gap
flashing or MOV conducting are neglected. The time dependence of fault currents
and the difference between them are of interest.
en06000609.vsd
~
e
G
(t)
i
L
(t)
R
L
jX
L
-jX
C
F
IEC06000609 V1 EN-US
Figure 83: Simplified equivalent scheme of SC network during fault conditions
We consider the instantaneous value of generator voltage following the sine wave
according to equation
53
( )
sin
w l = × × +
G G
e E t
EQUATION1904 V1 EN-US (Equation 53)
The basic loop differential equation describing the circuit in figure
83 without
series capacitor is presented by equation 54
( )
sin
w l × + × = × × +
L
L L L G
di
L R i E t
dt
EQUATION1905 V1 EN-US (Equation 54)
The solution over line current is presented by group of equations 55
( )
( )
( )
( )
0
2
2
sin sin
w l j l j
w
w
j
- ×
=
é ù
= × × + - + - × - ×
ê ú
ë û
= + ×
æ ö
×
=
ç ÷
è ø
L
L
R
t
L
G G
L
L t
L L
L
L
E E
i t I e
Z Z
Z R L
L
atg
R
EQUATION1906 V1 EN-US (Equation 55)
The line fault current consists of two components:
• The steady-state component which magnitude depends on generator voltage
and absolute value of impedance included in the circuit
• The transient DC component, which magnitude depends on the fault incident
angle decays with the circuit time constant
[ ]
L L
L R s
EQUATION1907 V1 EN-US (Equation 56)
Section 8 1MRK 506 369-UEN B
Impedance protection
174 Line distance protection REL670 2.2 IEC
Application manual