1.16
SEL-751A Relay Instruction Manual Date Code 20100129
Introduction and Specifications
Getting Started
Getting Started
Understanding basic relay operation principles and methods will help you use
the SEL-751A effectively. This section presents the fundamental knowledge
you need to operate the SEL-751A, organized by task. These tasks help you
become familiar with the relay and include the following:
➤ Powering the relay
➤ Establishing communication
➤ Checking relay status
➤ Setting the date and time
Perform these tasks to gain a fundamental understanding of relay operation.
Powering the Relay
Power the SEL-751A with 125/250 Vac/dc or 24/48 Vdc, depending on the
part number.
➤ Observe proper polarity, as indicated by the +/H (terminal A01)
and the –/N (terminal A02) on the power connections.
➤ Connect the ground lead; see Grounding (Earthing)
Connections on page 2.17.
➤ Once connected to power, the relay does an internal self-check
and the ENABLED LED illuminates.
Establishing
Communication
The SEL-751A has two EIA-232 serial communications ports. The following
steps require PC terminal emulation software and an SEL Cable C234A (or
equivalent) to connect the SEL-751A to the PC. See Section 6: Settings for
further information on serial communications connections and the required
cable pinout.
Step 1. Connect the PC and the SEL-751A using the serial
communications cable.
Step 2. Apply power to both the PC and the relay.
Step 3. Start the PC terminal emulation program.
Step 4. Set the PC terminal emulation program to the communications
port settings listed in the Default Value column of Table 1.2.
Also, set the terminal program to emulate either VT100 or
VT52 terminals.
Step 5. Press the <Enter> key on the PC keyboard to check the
communications link.
You will see the
= prompt at the left side of the computer screen
(column 1).
If you do not see the
= prompt, check the cable connections,
and confirm that the settings in the terminal emulation program
are the default values in Table 1.2.
Step 6. Type QUIT <Enter> to view the relay report header.
You will see a computer screen display similar to Figure 1.2. If
you see jumbled characters, change the terminal emulation type
in the PC terminal emulation program.
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