ABB RET670 Applications Manual page 236

Section 3
IED application
230
< < +
X X X X
11 C S 11
EQUATION1898 V1 EN
and in figure 99
a three phase fault occurs beyond the capacitor. The resultant IED impedance seen
from the D IED location to the fault may become negative (voltage inversion) until
B
the spark gap has flashed.
Distance protections of adjacent power lines shown in figure
negative impedance. If the intermediate infeed of short circuit power by other lines is
taken into consideration, the negative voltage drop on X
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
= + +
I I I I
1 2 3
EQUATION1915 V1 EN
I
(
= - × -
X X F X
DA 1 A 1 C
I
A 1
EQUATION1916 V1 EN
I
(
= - ×
X X F X
DA 2 A 2 C
I
A 2
EQUATION1917 V1 EN
I
(
= - ×
F
X X X
DA 3 A 3 C
I
A 3
EQUATION1918 V1 EN
142 to 145.
)
X
11
)
-
X
11
)
-
X
11
1MRK504116-UUS C
(Equation 141)
99 are influenced by this
is amplified and a protection
C
(Equation 142)
(Equation 143)
(Equation 144)
(Equation 145)
Application manual