EQUATION1898 V1 EN-US (Equation 340)
and in figure
216
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
216 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 341 to 344.
EQUATION1915 V1 EN-US (Equation 341)
X X
I
I
X X
DA A
F
A
C1 1
1
11
= + ⋅ −
( )
EQUATION1916 V2 EN-US (Equation 342)
X X
I
I
X X
DA A
F
A
C2 2
2
11
= + ⋅ −
( )
EQUATION1917 V2 EN-US (Equation 343)
X X
I
I
X X
DA A
F
A
C3 3
3
11
= + ⋅ −
( )
EQUATION1918 V2 EN-US (Equation 344)
Section 8 1MRK 504 163-UUS A
Impedance protection
428 Transformer protection RET670 2.2 ANSI
Application manual
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