10.25
Date Code 20170601 Instruction Manual SEL-387-0, -5, -6 Relay
Testing and Troubleshooting
Acceptance Testing
SLP2 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, and the restraint current slope 1 limit (IRS1)
setting.
b. Execute the SET W1CTC <Enter> command and set
the WnCTC settings for the two windings to be used to
the same value.
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: Decide where you want to cross the differential
characteristic by picking a restraint value IRT that is a vertical
line on the graph. Since this test is for the SLP2 threshold,
select a point above the IRS1 setting.
IRT > IRS1
The value of IOP that corresponds to the selected IRT is as
follows:
Equation 10.9
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 SLP2 threshold
for the test point selected above.
Method: Calculate the Winding 1 current for the test using the
following formula:
Equation 10.10
Calculate the Winding 2 current for the test using the following formula:
. Equation 10.11
The A connection compensation constant is based on
Table 10.4. Since the windings have the same WnCTC setting,
the A constant will be the same for both windings. The A
NOTE: For this test, use only
WnCTC = 0 or WnCTC = an odd-
numbered setting (1, 3, 5, 7, 9, 11).
Depending on the value of IRT
selected in step 3 below, the even-
numbered settings may produce 87R
outputs from 87R-2 and 87R-3 before
the calculated slope 2 current (below)
reaches the curve value for 87R-1. This
could lead to erroneous conclusions
about the accuracy of the 87R
elements.
IOP
SLP2
100
-------------- IRT IRS1
SLP1 SLP2–
100
----------------------------------
• +• =
IAW1 IRT 1
SLP2
200
--------------+
RS1
SLP1 SLP2–
200
----------------------------------
• +•
TAP1 A• • =
IAW2 IRT 1
SLP2
200
--------------–
IRS1
SLP1 SLP2–
200
----------------------------------
• –•
TAP2 A• • =
The continuous rating of the current
inputs is 3 • I
NOM
. If any currents in
this test will exceed this rating, reduce
the TAPn values as needed, to prevent
possible damage to the input circuits.
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