ABB RET670 - Page 236

11 11
< < +
C S
X X X X
EQUATION1898 V1 EN (Equation 141)
and in figure 99
a three phase fault occurs beyond the capacitor. The resultant IED impedance seen
from the D
B
IED location to the fault may become negative (voltage inversion) until
the spark gap has flashed.
Distance protections of adjacent power lines shown in figure
99 are influenced by this
negative impedance. If the intermediate infeed of short circuit power by other lines is
taken into consideration, the negative voltage drop on X
C
is amplified and a protection
far away from the faulty line can maloperate by its instantaneous operating distance
zone, if no precaution is taken. Impedances seen by distance IEDs on adjacent power
lines are presented by equations 142 to 145.
1 2 3
= + +I I I I
EQUATION1915 V1 EN (Equation 142)
( )
1 1 11
1
= - × -
F
DA A C
A
I
X X X X
I
EQUATION1916 V1 EN (Equation 143)
( )
2 2 11
2
= - × -
F
DA A C
A
I
X X X X
I
EQUATION1917 V1 EN (Equation 144)
( )
3 3 11
3
= - × -
F
DA A C
A
I
X X X X
I
EQUATION1918 V1 EN (Equation 145)
Section 3 1MRK504116-UUS C
IED application
230
Application manual