Date Code 20020129
Testing and Troubleshooting
10-25
SEL-387E Instruction Manual
Step 4.
Purpose: Calculate the expected current for Windings 1 and 2 at the restrained
differential element SLP1 threshold for the test point selected above.
Method: Calculate the Winding 1 current for the test using the following formula:
A
•
1
TAP
•
200
1
SLP
1
•
IRT
1
IAW
ÜÜÝ
Û
ÌÌÍ
Ë
+
=
Calculate the Winding 2 current for the test using the following formula:
A
•
2
TAP
•
200
1
SLP
1
•
IRT
2
IAW
ÜÜÝ
Û
ÌÌÍ
Ë
-
=
The A connection compensation constant is based on Table 10.3.
Because the windings have the same WnCTC 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
TAPn settings can be different for the two windings.
&$87,21
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.
Step 5.
Purpose: Calculate the initial current for Winding 2 for this test.
Method: Calculate the Winding 2 initial current for the test using the following
formula:
1
TAP
2
TAP
•
1
IAW
2
IAW
=
This formula determines the current necessary for IOP = 0 given the
IAW1 calculated above.
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: Connect the two current test sources as shown in Figure 10.6. Turn on the
current test source for A-phase of Winding 1 (IAW1) at the value
calculated above,
and set the phase angle at zero degrees
. Turn on the
current test source for A-phase of Winding 2 (IAW2) at the calculated
initial current
and set the phase angle at 180 degrees
. Slowly decrease
the magnitude of IAW2 until the 87R element asserts. Note the
magnitude of the current applied. It should equal the value calculated in
step 4 ±5% ±0.02 I
nom
.
Содержание SEL-387E
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