7-28 Maintenance and Testing Date Code 20000421
SEL-251, -2, -3 Instruction Manual
When the trip failure timer expires, trip failure condition bit TF and the A4
output contact assert (A4 = TF). A4 output contact assertion stops the external
timer. Compare the external timer reading to the trip failure time setting (TFT =
30 cycles in this example). The TF bit deasserts 60 cycles after you turn the
current off.
Input Circuits Test
Purpose: Verify that logic inputs assert when you apply control voltage across respective
terminal pairs.
Method: 1. Set the target LEDs to display the contact inputs by typing TAR 7 <ENTER>.
The front panel LEDs should now follow contact inputs.
2. Apply control voltage to each input and make sure the corresponding target LED
turns on. Energizing the DT and ET inputs should trigger an event report. Table
7.3 lists contact inputs and terminal numbers.
Table 7.3: Contact Inputs and Terminal Numbers
IN1
IN2
IN3
IN4
IN5
IN6
17, 18
19, 20
21, 22
23, 24
25, 26
27, 28
Serial Ports Test
Purpose: Verify operation of serial Port 1.
Method: The initial checkout procedure assumes you connected a terminal to Port 2F on the
relay front panel. Set the baud rate of Port 1 to match that of Port 2 and switch your
terminal from Port 2F to Port 1. Be sure you can communicate through this port.
IRIG-B Time Code Input Test
Purpose: Verify operation of the IRIG-B clock input port.
Method: 1. Connect a source of demodulated IRIG-B time code to the relay Auxiliary Port in
series with a resistor to monitor the current. Adjust the source to obtain an "ON"
current of about 10 mA.
2. On the plug-in connector model, Ports 1 and 2R may be configured to accept
demodulated IRIG-B input. When JMP13 and JMP14 are bridged, pins 6 and 4
will accept -IRIG-B and +IRIG-B, respectively. See Table 3.2 for port pinouts.
3. Execute the IRIG command. Make sure the relay clock displays the correct date
and time.
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