Date Code 20020129
Testing and Troubleshooting
10-19
SEL-387E Instruction Manual
Slowly reduce IAW2 until the unit picks up, indicated by LED A. This
should happen when IAW2 equals 10 - 51PC1P. After verifying pickup,
increase IAW2 back to 10 A. LED A will extinguish. Wait for LED C to
reappear, indicating reset. Or, issue command
RES
to force a reset.
Suddenly reduce the current IAW2 to a value equal to 10 - M
•
51PC1P,
where M is the desired multiple of pickup. Allow the unit to proceed to
time-out, indicated by the lighting of LED B. (LED A will also be lit.)
Step 4.
Purpose: Verify the operation time.
Method: Type
SER<ENTER>
to view the sequential events records. The
assertion and deassertion of each element listed in the SER1, 2, 3, and 4
settings are recorded. Subtract the time of the assertion of the pickup
(i.e., 51PC1) from the assertion time of the time-out bit (i.e., 51PC1T).
This is the operate time.
SER C
clears the sequential events records.
Step 5.
Purpose: Repeat the test for 51NC1.
Method: Repeat Steps 1 through 4 for the other elements. Remember to set the
SER for the appropriate elements and apply current to the appropriate
winding. Also remember to disable the pickup of the complementary
element in each set, so that only the phase or residual element is being
tested at one time.
Restricted Earth Fault (REF) Function
The test for the REF function is similar to that for the combined overcurrent element–using two
current sources to inject current into two different windings. Small currents are used to
demonstrate the sensitivity of the element to internal ground faults. The test assumes a 5 A relay
is being used.
The settings for the REF function are these:
E32I
=
Enabling
SEL
OGIC
control equations. Set E32I = 1.
32IOP = Winding(s) for obtaining the Operate quantity. Set 32IOP = 1.
a0
= Positive-sequence restraint factor. Use default setting, a0 = 0.1.
50GP = Residual current sensitivity level. Use default setting, 50GP = 0.5 A.
Recall that the default CT ratio settings are: CTR1 = 120, and CTR4 = 400.
Note:
To use the setting 50GP = 0.5, be sure that the ratio
CTRmax/CTR3 is not more than 2.0, where CTRmax is the
larger of CTR1 and CTR3. Using the default CT ratio settings,
CTRmax = CTR3, so the ratio CTRmax/CTR3 = 1. Therefore,
the 50GP setting can remain at 0.5A.
If the ratio CTRmax/CTR3 is greater than 2.0, set 50GP equal to
0.25 A times the actual ratio of CTRmax/CTR3.
