EQUATION1898 V1 EN (Equation 67)
and in figure 96
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
96 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
68 to 71.
EQUATION1915 V1 EN (Equation 68)
X X
I
I
X X
DA A
F
A
C1 1
1
11
= + ⋅ −
( )
EQUATION1916 V2 EN (Equation 69)
X X
I
I
X X
DA A
F
A
C2 2
2
11
= + ⋅ −
( )
EQUATION1917 V2 EN (Equation 70)
X X
I
I
X X
DA A
F
A
C3 3
3
11
= + ⋅ −
( )
EQUATION1918 V2 EN (Equation 71)
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 197
Application manual
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