Functions
6-19
7SA522 Manual
C53000-G1176-C119-2
Earth Impedance
(Residual)
Compensation
with Scalar Factors
R
E
/R
L
and X
E
/X
L
When entering the resistance ratio R
E
/R
L
and the reactance ratio X
E
/X
L
the addresses
to
apply. These ratios are simply formally calculated and are not identical
with the real and imaginary part of Z
E
/Z
L
. A computation with complex numbers is
therefore not necessary! The values may derived from the line data using the following
equations:
Resistance ratio:
Reactance ratio:
Whereby the following applies
R
0
— Zero sequence resistance of the line
X
0
— Zero sequence reactance of the line
R
1
— Positive sequence resistance of the line
X
1
— Positive sequence reactance of the line
These values may either apply to the entire line length or be based on a per unit of line
length, as the quotient is independent of length. Furthermore it makes no difference if
the quotients are calculated with primary or secondary values.
Calculation example:
110 kV overhead line 150 mm
2
with the following data
R
1
/s = 0.19
Ω
/km
X
1
/s = 0.42
Ω
/km
Positive sequence impedance
R
0
/s = 0.53
Ω
/km
X
0
/s = 1.19
Ω
/km
Zero sequence impedance
(where s = line length)
The following results are obtained for the earth impedance ratio:
The earth impedance (residual) compensation factor setting for the first zone Z1 may
be different from that of the remaining zones of the distance protection. This allows the
setting of the exact values for the protected line, while at the same time the setting for
the back-up zones may be a close approximation even when the following lines have
substantially different earth impedance ratios (e.g. cable after an overhead line). Ac-
cordingly, the settings for the address
and
are
determined with the data of the protected line while the addresses
apply to the remaining zones Z1B
and Z2 up to Z5 (as seen from the relay location).
R
E
R
L
-------
1
3
---
R
0
R
1
-------
1
–
⋅
=
X
E
X
L
-------
1
3
---
X
0
X
1
------
1
–
⋅
=
R
E
R
L
-------
1
3
---
R
0
R
1
-------
1
–
⋅
1
3
---
0.53
Ω
/km
0.19
Ω
/km
-----------------------------
1
–
0.60
=
⋅
=
=
X
E
X
L
-------
1
3
---
X
0
X
1
------
1
–
⋅
1
3
---
1.19
Ω
/km
0.42
Ω
/km
-----------------------------
1
–
0.61
=
⋅
=
=
Summary of Contents for siprotec 7SA522
Page 20: ...7SA522 Manual C53000 G1176 C119 2 ...
Page 64: ...7SA522 Manual C53000 G1176 C119 2 ...
Page 89: ...SIPROTEC 4 Devices 4 25 7SA522 Manual C53000 G1176 C119 2 Figure 4 20 CFC Logic example ...
Page 408: ...7SA522 Manual C53000 G1176 C119 2 ...
Page 456: ...7SA522 Manual C53000 G1176 C119 2 ...
Page 516: ...7SA522 Manual C53000 G1176 C119 2 ...
Page 620: ...Appendix B 48 ...
