10.23
Date Code 20170601 Instruction Manual SEL-387-0, -5, -6 Relay
Testing and Troubleshooting
Acceptance Testing
SLP1 Restrained Differential Threshold
Step 1. Purpose: Verify the differential characteristic settings and set
winding compensation.
Method:
a. Execute the SHO TAP1 <Enter> command via the
relay front panel or serial port and verify the (TAPn)
settings, the Restraint Slope 1 Percentage (SLP1)
setting, the Restraint Slope 2 Percentage (SLP2)
setting, the restraint current slope 1 limit (IRS1) setting,
and the O87P minimum pickup setting.
b. Execute the SET W1CTC <Enter> command and set
the WnCTC settings for the two windings to be used to
the same value (0, 1, …, 12).
c. Save the settings.
Step 2. Purpose: Display the appropriate Relay Word bit on the front-
panel LEDs.
Method: Execute the TARGET command (i.e., TAR F 87R
<Enter>). The SEL-387 now displays the state of several
differential elements in the second row of the front-panel
LEDs. The 87R bit is the right-most LED.
Step 3. Purpose: Select a test point on the percentage differential curve
in Figure 10.6.
Method:
a. Decide where you want to cross the differential
characteristic by picking a restraint value IRT that is a
vertical line on the graph.
b. Since this test is for the SLP1 threshold, select a point
above the O87P intersection point and below IRS1. If
SLP2 = OFF, IRS1 and SLP2 are not functional.
O87P • 100/SLP1 < IRT < IRS1
The value of IOP corresponding to the selected IRT
equals the following:
Equation 10.4
Both IRT and IOP are in multiples of tap.
Step 4. Purpose: Calculate the expected current for Winding 1 and
Winding 2 at the restrained differential element SLP1 threshold
for the test point selected above.
Method:
a. Calculate the Winding 1 current for the test using the
following formula:
Equation 10.5
b. Calculate the Winding 2 current for the test using the
following formula:
Equation 10.6
IOP
SLP1
100
-------------- IRT• =
IAW1 IRT 1
SLP1
200
--------------+
TAP1 A• • • =
IAW2 IRT 1
SLP1
200
--------------–
TAP2 B• • • =
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