Distance Protection With Mho Characteristic (Optional); Functional Description - Siemens siprotec 7SD5 User Manual

2 Functions
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 One MHO characteristic is defined for each distance zone, which represents the trip-
Characteristic 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
of inclination is set in address 1540 Distance Angle and corresponds normally to
the line angle ϕ
cut the area of the load impedance out of the characteristic. The reach Z
arately set for each zone; the inclination angle ϕ
rameters R
origin of the coordinate system, a separate directional characteristic is not required.
150
which determines the reach, and by the angle of inclination. The angle
r
. A load trapezoid with the setting R
Line
, and ϕ
are common to all zones. As the characteristic intersects the
Load Load
and ϕ
may be used to
Load Load
r
as well as the load impedance pa-
Dist
C53000-G1176-C169-1
may be sep-
7SD5 Manual