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3 zone impedance protection (Z(n)RW)
a)
I
U
I
N
)LJXUH (TXLYDOHQW FLUFXLW IRU PHDVXULQJ VLQJOHSKDVH WR HDUWK IDXOW LQ WZR SKDVH
JURXQGHG V\VWHPV
Each return impedance is equal to the expression:
1
⋅
(
)
Z
Z
Z
=
-- -
–
N
0
1
2
The total impedance, according to figure 35, is equal to:
Z
Z
Z
R
=
+
+
loop
1
N
F
The range of a distance protection zone is related to the positive sequence impedance,
Z
. Accordingly, the zero sequence compensation factor K
1
the measuring algorithm. Its value is equal to:
Z
Z
1
⋅
N
0
-- -
K
=
=
------ -
------ ------------
N
2
Z
Z
1
3KDVHWRSKDVH IDXOWV
A measurement loop with phase to phase fault consists of the impedances shown in fig-
ure 36, where:
L1
F
L2
⋅
(
) R
= Z
1 K
+
+
1
N
F
Z
–
1
1
&KDSWHU
/LQH LPSHGDQFH
b)
Z
I
1
U
Z
N
en02000643.vsd
has been introduced into
N
R
F
(Equation 24)
(Equation 25)
(Equation 26)
69
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