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2 Functions
In the case of parameterization with secondary quantities, the values derived from the
grading coordination chart must be converted to the secondary side of the current and
voltage transformers. In general:
Accordingly, the reach for any distance zone can be specified as follows:
with
N
N
On long, heavily loaded lines, the MHO characteristic may extend into the load imped-
ance range. This is of no consequence as the pickup by overload is prevented by the
load trapezoid. Refer to margin heading „Load Area" in Section 2.5.1.
Calculation Example:
110 kV overhead line 150 mm
s (length)
Current Transformer
Voltage Transformer
The following line data is calculated:
R
X
For the first zone, a setting of 85 % of the line length should be applied, which results
in primary:
X1
or secondary:
Each zone can be set using the parameter MODE Forward or Reverse (address
Independent Zones
1701 Op. mode Z1, 1711 Op. mode Z2, 1721 Op. mode Z3, 1731 Op. mode
Z1 up to Z5
Z4 and 1741 Op. mode Z5). This allows any combination of forward or reverse
graded zones. Zones that are not required, are set Inactive.
The values derived from the grading coordination chart are set for each of the required
zones. The setting parameters are grouped for each zone. For the first zone these are
158
= Current transformer ratio
CT
= Transformation ratio of voltage transformer
VT
= 35 km
= 0.19 Ω/km
R
/s
1
= 0.42 Ω/km
X
/s
1
= 0.53 Ω/km
R
/s
0
= 1.19 Ω/km
X
/s
0
600 A / 5 A
110 kV / 0.1 kV
= 0.19 Ω/km · 35 km = 6.65 Ω
L
= 0.42 Ω/km · 35 km = 14.70 Ω
L
= 0.85 · 14.70 Ω= 12.49 Ω
= 0.85 · X
prim
L
2
with the following data:
7SD5 Manual
C53000-G1176-C169-1
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