7.15
Date Code 20150130 Instruction Manual SEL-787 Relay
Communications
SEL ASCII Protocol and Commands
The relay transmits XOFF (ASCII hex 13) when the buffer is more than
75 percent full. If hardware handshaking is enabled, the relay deasserts the
RTS output when the buffer is approximately 95 percent full. Automatic
transmission sources should monitor for the XOFF character to avoid
overwriting the buffer. Transmission should terminate at the end of the
message in progress when XOFF is received and can resume when the relay
sends XON.
The CAN character (ASCII hex 18) aborts a pending transmission. This is
useful for terminating an unwanted transmission. You can send control
characters from most keyboards with the following keystrokes:
➤ XOFF: <Ctrl+S> (hold down the <Ctrl> key and press S)
➤ XON: <Ctrl+Q> (hold down the <Ctrl> key and press Q)
➤ CAN: <Ctrl+X> (hold down the <Ctrl> key and press X)
Automatic Messages
When the serial port AUTO setting is Y, the relay sends automatic messages to
indicate specific conditions. Table 7.5 lists these messages.
Access Levels
Commands can be issued to the SEL-787 via the serial port or Ethernet Telnet
session to view metering values, change relay settings, etc. The available
serial port commands are listed in the SEL-787 Relay Command Summary at
the end of this manual. These commands can be accessed only from the
corresponding access level, as shown in the SEL-787 Relay Command
Summary. The access levels are:
➤ Access Level 0 (the lowest access level)
➤ Access Level 1
➤ Access Level 2 (the highest access level)
➤ Access Level C (restricted access level, should be used under
direction of SEL only)
Access Level 0
Once serial port communication is established with the SEL-787, the relay
sends the following prompt:
This is referred to as Access Level 0. Only a few commands are available at
Access Level 0. One is the ACC command. See the SEL-787 Relay Command
Summary at the end of this manual. Enter the ACC command at the Access
Level 0 prompt:
Table 7. 5 S e r ial Po r t Au tomatic M e ssages
Condition Description
Power Up The relay sends a message containing the present date and
time, Relay and Terminal Identifiers, and the Access Level 0
prompt when the relay is turned on.
Event Trigger The relay sends an event summary each time an event report
is triggered. See Section 9: Analyzing Events.
Self-Test Warning or
Failure
The SEL-787 sends a status report each time a self-test
warning or failure condition is detected. See STATUS
Command (Relay Self-Test Status) on page 7.40.
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