10.12
SEL-387-0, -5, -6 Relay Instruction Manual Date Code 20170601
Testing and Troubleshooting
Acceptance Testing
Definite-Time and Inverse-Time Overcurrent Elements
Step 1. Purpose: Determine the expected time delay for the overcurrent
element.
Method:
a. Execute the SHO command via the relay front panel or
serial port and verify the time delay settings (i.e., SHO
51P1 <Enter>). The delay settings will follow the
pickup settings when they are displayed.
b. Calculate the time delay to pickup (tp).
Definite-time elements will be equal to the delay setting
(i.e., 50P11D setting for the 50P11 element). Inverse-
time elements are calculated using three element
settings and the operating time equations shown in
Section 3: Differential, Restricted Earth Fault,
Thermal, and Overcurrent Elements. TD is the time-
dial setting (i.e., 51P1TD), and M is the applied
multiple of pickup current.
For example, if 51P1P = 2.2 A, 51P1C = U3, and
51P1TD = 4.0, we can use the equation below to
calculate the expected operating time for M = 3
(applied current equals M • 51P1P = 6.6 A):
Equation 10.1
Step 2. Purpose: Set the Sequential Events Recorder to record the
element timing.
Method:
a. Use SET R SER1 <Enter> to set SER1 equal to the
element pickup and time-out Relay Word bits (i.e.,
51P1, 51P1T).
b. When prompted, set SER2, SER3, and SER4 to NA.
Save the settings.
Step 3. Purpose: Connect and apply a single current test source at a
level that is M times greater than the pickup (i.e., 2.2 • M =
6.6 A for this example).
Method:
a. Connect a single current test source as shown in
Figure 10.5.
b. Turn on the single current test source for the winding
under test at the desired level.
Step 4. Purpose: Verify the operation times.
Method:
a. Type SER <Enter> to view the SER. The assertion and
deassertion of each element listed in the SER1, 2, 3,
and 4 settings are recorded.
b. Subtract the time from the assertion of the pickup (i.e.,
51P1) to the assertion of the time-delayed element (i.e.,
51P1T). SER C clears the SER records.
NOTE: This example tests the
Winding 1 51P1 phase inverse-time
overcurrent element. Use the same
procedure to test all definite-time and
inverse-time overcurrent elements for
each winding.
tp TD 0.0963
3.88
M
2
1–
----------------+
• =
tp 2.33 seconds=
NOTE: If the time-overcurrent
element induction-disk reset
emulation is enabled (i.e., 51P1RS = Y),
the element under test may take some
time to reset fully. If the element is not
fully reset when you run a second test,
the time to trip will be lower than
expected. To reset all time-
overcurrent elements before running
additional tests, enter the RESET
<Enter> command from the relay serial
port.
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