BECKWITH ELECTRIC M-3425A, Instruction Book

Page: 342 / 482

6–55
Testing – 6
Blocking on Stable Swing Test:
1. While monitoring the Positive Sequence Impedance, set the magnitude and phase angle of the Input
Currents to a point outside of the mho circle.
2. While monitoring the Positive Sequence Impedance, set the magnitude and phase angle of the Input
Currents to point
Z
0
in Figure 4-79.
3. Press and hold the
TARGET RESET
pushbutton, then sweep past point
Z
1
.
When the impedance passes through point
Z
1
, verify that the
78 OUT OF STEP
LED illuminates,
or the function status indicator on the
Monitor Function Status
screen indicates that the function
has picked up.
4. Pause testing until the delay timer has time to expire, then reverse the sweep direction and sweep
the current angle to point
Z
1
.
As point
Z
1
is crossed, verify output
Z
does not operate and the
78 OUT OF STEP
LED extinguishes
or the function status indicator on the
Monitor Function Status
screen indicates that the function
has reset.
6. If testing is complete, then reduce voltages and currents to zero.
Pickup Test (Trip on mho Exit):
1. Enable the
TRIP ON MHO EXIT
setting.
2. While monitoring the Positive Sequence Impedance, set the magnitude and phase angle of the Input
Currents to point
Z
0
in Figure 4-79.
3. Press and hold the
TARGET RESET
pushbutton, then sweep the current angle towards point
Z
1
.
When the impedance passes through point
Z
1
, verify that the
78 OUT OF STEP
LED illuminates or
the function status indicator on the
Monitor Function Status
screen indicates that the function has
picked up.
4. Pause testing until the delay timer has time to expire, then continue to sweep the current angle to
beyond point
Z
2
. Verify that output
Z
does not operate as point
Z
2
is crossed.
5. Sweep the impedance further towards point
Z
3
. Verify output
Z
operates as point
Z
3
is crossed, and
resets after the seal-in time delay has timed out.
6. If testing is complete, then reduce voltages and currents to zero.