ERL L-PRO 4000, User Manual

Page: 67 / 406

4 Protection Functions and Specifications
D02706R02.30 L-PRO 4000 User Manual 4-17
68 Power Swing
The Power Swing function can be used as a tripping or blocking function. This
function consists of 2 sets of inner and outer impedance Zones on the R-X
plane, for details see If the user selects Device 68 to block for Power Swing
conditions, the relay energizes the front panel alarm LED when the 68 ele-
ments are blocking. If the user selects the 68 to trip for Power Swing conditions
the relay energizes the front panel target light. on page 4-17. Set the Power
swing zones to different values and to have the Power Swing function operate
for different system conditions. The Power swing zones are quadrilateral char-
acteristic and the reactance lines with the same angle as the angle chosen for
the line positive sequence impedance. Outputs from the outer and the inner
power swing zones are available on the output matrix for use with other types
of Power Swing schemes or for monitoring.
Figure 4.11: Power Swing Characteristic
The basic Power Swing scheme looks at the positive sequence impedance of
the line with respect to the line loading. If the line loading causes the imped-
ance to cross the outer Zone, an Power Swing timer is started. If the impedance
does not cross the inner zone before this timer times out, the function produces
an output (either a block or trip whichever is set) when the impedance crosses
the inner Zone. The entire activity is supervised by an overcurrent function to
prevent undesired operations for impedances far from the origin.
The logic has a timeout feature that prevents the blocking function from oper-
ating for an indefinite amount of time. Device 68 functions as either a blocking
device or tripping device. The 68 Power Swing (68 Trip or 68 Block), 68 Inner
and 68 Outer Zone logic points are available in the output matrix. These logic
points are also logged as event messages in the event log, “Event Messages”
in Appendix D In addition, the outputs from the inner and outer Zones are
available for use with ProLogic to create any application scheme required.
If the user selects Device 68 to block for Power Swing conditions, the relay en-
ergizes the front panel alarm LED when the 68 elements are blocking. If the
user selects the 68 to trip for Power Swing conditions the relay energizes the
front panel target light.
Zone 5
Zone 3
Zone 2
Zone 1
Zone 4
Line Z1
Line Angle
R
X
X3
X4
X2
X1
R4 R3 R1 R2