2.2 Distance protection
97
7SA522 Manual
C53000-G1176-C155-3
For each distance zone a MHO circle can be defined by means of the parameter Z
r
. It
can also be determined for each zone whether its sense of action is forward or re-
verse. In the reverse direction, the MHO circle is mirrored in the origin of the coordi-
nate system. As soon as the fault impedance of any loop is reliably measured inside
the MHO circle of a distance zone, the affected loop is designated as “picked up”. The
loop information is also converted to phase-segregated information. Further condi-
tions for the pick-up of a zone is that the zone may not be blocked by the power swing
blocking. Furthermore, the distance protection may not be blocked or switched off
completely. Figure 2-29 shows these conditions.
The zones and phases of such a valid pickup, e.g. “Dis.Z1 L1E” for zone Z1 and phase
L1 are processed by the zone logic and the supplementary functions (e.g. teleprotec-
tion logic).
Figure 2-29 Release logic of a zone (example for Z1)
*) forward and reverse only affect the measured quantities and not the logic
In total, the following zones are available:
Independent zones:
• 1st zone (fast tripping zone) Z1 with =5=; may be delayed by 7SKDVH and
7PXOWLSKDVH,
• 2nd zone (backup zone) Z2 with =5=; may be delayed by 7SKDVH and 7
PXOWLSKDVH,
• 3rd zone (backup zone) Z3 with =5=; may be delayed by 7'(/$<,
• 4th zone (backup zone) Z4 with =5=; may be delayed by 7'(/$<,
• 5th zone (backup zone) Z5 with =5=; may be delayed by 7'(/$<.
Dependent (controlled) Zone:
• Overreaching zone Z1B with =5=%; may be delayed by 7%SKDVH and / or
7%PXOWLSKDVH.
2.2.3.2 Setting Notes
General The function parameters for the MHO circle characteristic only apply if during the con-
figuration of the scope of functions the MHO- circle was selected for phase-phase
measurement (address ) and/or phase-earth measurement (address ).
To Next Page
Loading...
Need help?
General
