Siemens siprotec 7SA522, User Manual

Page: 222 / 628

Functions
6-74
7SA522 Manual
C53000-G1176-C119-2
A power swing is detected, if during the last eight measuring cycles (corresponding to
two periods), the continuity of the changing impedance vector is confirmed. In this
way, slip frequencies of up to at least 7 Hz are detected.
Figure 6-42 Pick up characteristic for the power swing detection for the MHO circle
Power Swing
Blocking The power swing blocking affects the distance protection. If the criteria for power
swing detection have been fulfilled in at least one phase, the following reactions are
possible in relation to the power swing blocking function (set in address
36
2SPRGH
•
Blocking of all zones (
$OO]RQHVEORFN
):
All zones of the distance protection are blocked during a power swing.
•
Blocking of the first zone only (
==%EORFN
):
The first zone (Z1) and the overreaching zone (Z1B) are blocked during a power
swing. Faults in other zones are tripped with the associated grading time.
•
Blocking of only the higher zones (
=WR=EORFN
):
The higher zones (Z2 to Z5) are blocked during a power swing. Only the first and
the overreaching zone (Z1 and Z1B) remain active.
•
Blocking of the first two zones (
==%=EORFN
):
The first and second zone (Z1 and Z2) and the overreaching zone (Z1B) are
blocked during a power swing. The higher zones Z3 to Z5 remain active.
The associated measures taken only apply to those phases in which the power swing
has been detected. They are active for as long as the measured impedance vector is
inside the power swing range PPOL, or if due to an abrupt change of the associated
impedance vector the power swing criteria are no longer satisfied.
If the distance protection recognizes a short-circuit which results in a trip, during a
power swing, this trip signal is always three-pole.
X
R
PPOL
APOL
PPOL
APOL
Z
Diff