10.28
SEL-387-0, -5, -6 Relay
Instruction Manual
Date Code 20050919
Testing and Troubleshooting
Acceptance Testing
Equation 10.11
The A connection compensation constant is based on
. Since the windings have the same W
n
CTC setting,
the A constant will be the same for both windings. The A
constant must be used to achieve the exact curve point on
which we have based the calculations. The TAP
n
settings can
be different for the two windings.
Step 5. Purpose: Calculate the initial current for Winding 2 for this test.
Method: Calculate the Winding 2 initial current by multiplying
the Winding 2 expected current calculated above by 110
percent.
IAW2 (initial) = 1.1 • IAW2 (from step 4)
Step 6. Purpose: Connect a single current test source to A-phase of
Winding 1 and a single current test source to A-phase of
Winding 2. Ramp down Winding 2 current until the appropriate
LED illuminates.
Method:
a. Connect the two current test sources as shown in
b. Turn on the current test source for A-phase of
Winding 1 (
IAW1
) at the value calculated above
and set
the phase angle to zero degrees
.
c. Turn on the current test source for A-phase of
Winding 2 (
IAW2
) at the calculated starting current
and
set the phase angle at 180 degrees
.
d. Slowly decrease the magnitude of current
IAW2
until the
87R element asserts. Note the magnitude of the current
applied. It should equal the value calculated in
±5% ±0.02 I
NOM
.
Step 7. Purpose: Repeat the test for each phase for each winding
combination if desired.
Method:
a. Repeat
through
b. Remember to view the appropriate TARget and apply
current to the appropriate winding. The computer
terminal will display the LED labels from left to right
when the
TAR F
command is issued.
Second Harmonic Blocking
Step 1. Purpose: Verify the second-harmonic restraint percentage.
Method:
a. Execute the
SHOW
command via the relay front panel
or serial port and verify the percentage of fundamental
current that the magnitude of second-harmonic current
must exceed for differential restraint and that
HRSTR = N.
b. Enter
SHO PCT2 <Enter>
.
IAW2
IRT
1
SLP2
200
--------------
–
⎝
⎠
⎛
⎞
IRS1
SLP1
SLP2
–
200
----------------------------------
⎝
⎠
⎛
⎞
•
–
•
⎝
⎠
⎛
⎞
TAP2
A
•
•
=
!
CAUTION
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.
NOTE:
This test requires a current
source capable of generating second-
harmonic current. This example tests
the second-harmonic blocking
function.
Summary of Contents for SEL-387-0
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