( ) ( ) ( )
[ ]
( )
( ) ( )
( )
1 2
2
2
1 ( 0)
( 0) ( 0)
2
2
sin cos sin
1
sin
sin cos
2
1
sin
2
2
1
4
a
w l j b b
w
w
l j
w
l l j
b
l j
a
b
- ×
=
= =
= × × + - + × × + × × ×
= + × -
×
= - × -
× ×
× - - × - × - -
=
×
×
- × -
×
=
×
= -
× ×
æ ö
ç ÷
è ø
é ù
ê ú
ê ú
ê ú
ê ú
ë û
t
G
L
SC
SC L L
L
G
L t
SC
G L
L
G C t L t
SC
G L
L
SC
L
L
L
L L
E
i t K t K t e
Z
Z R L
C
E
K I
Z
E L
R
E V I
Z
K
E R
L
Z
R
L
R
L C L
2
L
EQUATION1996-ANSI V1 EN (Equation 61)
The transient part has an angular frequency b and is damped out with the time-constant α.
The difference in performance of fault currents for a three-phase short circuit at the end of
a typical 500 km long 500 kV line is presented in figure 86.
The short circuit current on a non-compensated line is lower in magnitude, but comprises
at the beginning only a transient DC component, which diminishes completely in
approximately 120ms. The final magnitude of the fault current on compensated line is
higher due to the decreased apparent impedance of a line (60% compensation degree has
been considered for a particular case), but the low frequency oscillation is also obvious.
The increase of fault current immediately after the fault incidence (on figure
86 at
approximately 21ms) is much slower than on non-compensated line. This occurs due to
the energy stored in capacitor before the fault.
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 187
Application manual
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