Siemens siprotec 7SD5, Руководство пользователя

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2 Functions
150
7SD5 Manual
C53000-G1176-C169-1
2.5.3 Distance Protection with MHO Characteristic (optional)
Depending on the version ordered, the universal line protection 7SD5 can be
equipped with an MHO characteristic in combination with the distance protection func-
tion. If both the polygonal and the MHO characteristic are available, they may be se-
lected separately for phase-phase loops and phase-earth loops. The polygonal trip-
ping characteristic is described in Section 2.5.2.
2.5.3.1 Functional Description
Basic
Characteristic One MHO characteristic is defined for each distance zone, which represents the trip-
ping characteristic of the corresponding zone. In total there are five independent and
one additional controlled zone for each fault impedance loop. The basic shape of a
MHO characteristic for one zone is shown in Figure 2-48 as an example.
The MHO characteristic is defined by the line of its diameter which intersects the origin
of the coordinate system and the magnitude of the diameter which corresponds to the
impedance Z
r
which determines the reach, and by the angle of inclination. The angle
of inclination is set in address
1540 Distance Angle
and corresponds normally to
the line angle
ϕ
Line
. A load trapezoid with the setting R
Load
and
ϕ
Load
may be used to
cut the area of the load impedance out of the characteristic. The reach Z
r
may be sep-
arately set for each zone; the inclination angle
ϕ
Dist
as well as the load impedance pa-
rameters R
Load
, and
ϕ
Load
are common to all zones. As the characteristic intersects the
origin of the coordinate system, a separate directional characteristic is not required.
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