Siemens siprotec 7SA6, Manual

Page: 209 / 876

Functions
6-19
7SA6 Manual
C53000-G1176-C156-2
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) matching 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
1116 RE/RL(Z1)
and
1117 XE/XL(Z1)
are
determined with the data of the protected line while the addresses
1118 RE/
RL(Z1B...Z5)
and
1119 XE/XL(Z1B...Z5)
apply to the remaining zones Z1B
and Z2 up to Z5 (as seen from the relay location).
Earth Impedance
(Residual)
Compensation with
Magnitude and
Angle (K
0
–Factor)
When the complex earth impedance (residual) matching factor K
0
is set, the address-
es
1120
to
1123
apply. In this case it is most relevant that the line angle is set cor-
rectly (cf Address
1105
, see paragraph “General Line Data”, page 17) as the device
needs the line angle to calculate the matching components from the K
0
–factor. These
factors are defined with their magnitude and angle which may be calculated with the
line data using the following equation:
Whereby the following applies
Z
0
— (complex) zero sequence impedance of the line
Z
1
— (complex) positive sequence impedance of the line
R
E
R
L
-------
1
3
---
R
0
R
1
------- 1
–
è ø
æ ö
⋅
=
X
E
X
L
-------
1
3
---
X
0
X
1
------ 1
–
è ø
æ ö
⋅
=
R
E
R
L
-------
1
3
---
R
0
R
1
------- 1
–
è ø
æ ö
⋅
1
3
---
0.53
Ω
/km
0.19
Ω
/km
----------------------------- 1
–
è ø
æ ö
0.60 =
⋅
= =
X
E
X
L
-------
1
3
---
X
0
X
1
------
1 –
è ø
æ ö
⋅
1
3
---
1.19
Ω
/km
0.42
Ω
/km
-----------------------------
1 –
è ø
æ ö
0.61 =
⋅
= =
K
0
Z
E
Z
L
-------
1
3
---
Z
0
Z
1
------ 1 –
è ø
ç ÷
æ ö
⋅
= =