BECKWITH ELECTRIC M-3520, Instruction Book

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M-3520 Instruction Book
6–38
78 Out of Step
VOLTAGE INPUTS : Configuration V1
CURRENT INPUTS : Configuration C1
TEST SETTINGS : Diameter P Ohms (0.1 to 100)
Offset O Ohms (–100 to +100)
Impedance Angle A Degrees (0 to 90)
Time Delay D Cycles (1 to 8160)
Blinder Impedance B Ohms (0.1 to 50.0)
Trip on MHO Exit See Below
Programmed Output Z
Delta-Y Transform Disable
Functions 21, 27, 27TN Disable
Functions 32, 51V Disable
Functions 81 Disable
■ ■ ■ ■ ■
NOTE : Use Figure 2-29 for reference. A stopwatch is required for this test.
1. Disable functions as shown. Refer to Section 3.2, Configure Relay Data, for procedure.
2. Confirm settings to be tested.
3. Connect inputs in Configuration V1 and C1 designated above. Refer to Section 6.1, Equipment/Test
Setup for configurations. Adjust voltage and currents while monitoring the positive sequence
impedance to a point similar to point
Z
0
in Figure 2-29.
4. Pickup Test: Disable the TRIP ON MHO EXIT setting and set the delay, D , to a minimal setting.
Press and hold the TARGET RESET button and sweep the current angle towards point Z
1
. When the
impedance passes through point Z
1
, verify that the OUT OF STEP 78 LED comes on or the function
status indicator shows the function picked up on the Monitor Function Status screen. Pause
testing until the delay timer has time to expire. Continue to sweep the current angle to point Z
2
, and
verify output Z operates as point Z
2
is crossed, and resets after the seal-in time delay.
Blocking on Stable Swing Test: Reset impedance to a point outside of the mho circle. Adjust
voltages and currents to point Z
0
. Press and hold the TARGET RESET button and sweep past point
Z
1
. Verify the OUT OF STEP 78 LED comes on or the function status indicator shows the function
picked up on the Monitor Function Status screen. Pause testing until the delay timer has time to
expire. Reverse sweep direction and sweep the current angle to point Z
1
, and verify output Z does not
operate and the OUT OF STEP 78 LED goes out or the function status indicator shows the function
reset on the Monitor Function Status screen as point Z
1
is crossed.
5. Pickup Test (Trip on mho Exit): Enable the TRIP ON MHO EXIT setting. Adjust voltages and
currents to point Z
0
. Press and hold the TARGET RESET button, and sweep the current angle
towards point Z
1
. When the impedance passes through point Z
1
, verify that the OUT OF STEP 78
LED comes on or the function status indicator shows that the function has picked up on the Monitor
Function Status screen. Pause testing until the delay timer has time to expire. Continue to sweep
the current angle to point Z
2
, and verify that output Z does not operate as point Z
2
is crossed. Sweep
the impedance further towards point Z
3
, and verify output Z operates as point Z
3
is crossed, and
resets after the seal-in time delay.