Schweitzer Engineering Laboratories SEL-352-1 - Circuit Breaker Close Resistor Thermal Failure Logic Test

Date Code 20010731 Testing and Troubleshooting 11-25
SEL-352-1, -2 Instruction Manual
stamps will also verify the APpu and AFpu timers. The APpu and AFpu times are
the times between the assertion of TRIPA and the assertion of LPF and LBF
respectively. Verify logic reset by looking for the deassertion of the LBF and LPF
elements.
CIRCUIT BREAKER CLOSE RESISTOR THERMAL FAILURE LOGIC TEST
Purpose: Verify operation of the breaker close resistor thermal failure logic (Reference:
Figure 3.19).
Method: 1. Using the SET command, set an output to close when the CTF element asserts,
and set the SER to trigger for the elements listed below. Verify the settings with
the SHO command and verify the SHO G command for 52AA, MCLOSE, and
CLOSE. Note that THLOG must be set to ON.
Setting
Elements
THLOG, 50MN,
26CF, 37OP, 87TH,
OPpu, 52AA,
MCLOSE, CLOSE
(47Q not used)
CTF, 50MNA, 37OPA, 87THA, OPAD,
52AA, MCLOSE, CLOSE
2. Use the HEA R command to reset the thermal models before each timing test.
3. Connect an external timer and set it to start when you apply A-phase current and
stop when the programmable output you set in Step 1 asserts.
4. Assert the CLOSE and/or MCLOSE input by applying dc control voltage to the
assigned input terminals.
5. Apply voltage greater than the 87TH setting to the A-phase voltage input.
Calculate a current magnitude such that applied power (Pa) is greater than the
37OP setting. Pa is defined:
Pa = Va
 Ia W
Where:
Pa = applied power
Va = applied phase voltage magnitude
Ia = applied phase current magnitude
Note: Applied current (Ia) must exceed 0.1 A to operate the CTF bit.
6. Calculate an estimated time to trip (TTT) in seconds by dividing the 26CF setting
by Pa:
s
Pa
CF26
TTT =