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Functions
2.1 General
Calculation Example:
110 kV overhead line 150 mm
R'
= 0.19 Ω/km
1
X'
= 0.42 Ω/km
1
The line angle is computed as follows
In address 1105 the setting Line Angle = 66° is entered.
Address 1511 Distance Angle specifies the angle of inclination of the R sections of the distance protection
polygons. Usually you can also set the line angle here as in address 1105.
The directional values (power, power factor, work and based on work: minimum, maximum, average and
threshold values), calculated in the operational measured values, are usually defined positive in the direction
towards the protected object. This requires that the connection polarity for the entire device was configured ac-
cordingly in the Power System Data 1 (compare also „Polarity of Current Transformers", address 201). But it
is also possible to define the „forward" direction for the protection functions and the positive direction for the
power etc. differently, e.g. so that the active power flow (from the line to the busbar) is indicated in the positive
sense. Set under address 1107 P,Q sign the option reversed. If the setting is not reversed (default),
the positive direction for the power etc. corresponds to the „forward" direction for the protection functions.
The reactance per unit length value X' of the protected line is entered as reference value x' in address 1111
in Ω/km if the distance unit was set as kilometer (address 236, see Section 2.1.2.1 at „Distance Unit"), or in
Ω/miles if mile was selected as distance unit. The corresponding line length is entered in address 1113 Line
Length in kilometers or in miles. If, after entry of the reactance per unit of line length in address 1111 or of the
line length in address 1113, the distance unit is changed in address 236, the line data must be entered again
for the revised distance unit.
The capacitance per unit length C' of the protected line is required for load current compensation, for double-
ended fault location and for compounding in overvoltage protection. Without these functions it is irrelevant. It is
entered as a reference value c' at address 1112 in μF/km if kilometres was set as the distance unit (address
236, see Section 2.1.2.1 at „Distance Unit"), or in μF/miles if mile was set as distance unit. If the distance unit
is changed in address 236 after entry of the capacitance per unit and of the line length in address 1112 or of
the line length in address 1113, the line data must be entered again for the changed distance unit.
For calculation of the capacitance of a line system, the entire line length, i.e. the sum of all line sections, must
be set in address 1114 Tot.Line Length. For lines with more than two ends, this information is required for
charging current compensation.
When entering the parameters with a personal computer running the DIGSI software, the values can also be
entered as primary values. If the nominal quantities of the primary transformers (U, I) are set to minimum,
primary values allow only a rough setting of the value parameters. In such cases it is preferable to set the pa-
rameters in secondary quantities.
For conversion of primary values to secondary values the following applies in general:
58
2
with the following data:
SIPROTEC, 7SD5, Manual
C53000-G1176-C169-5, Release date 02.2011
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