Date Code 20170601 Instruction Manual SEL-387-0, -5, -6 Relay
Appendix F
Unsolicited SER Protocol
Overview
This appendix describes special binary Sequential Events Recorder (SER)
messages that are not included in Section 9: Event Reports and SER of the
instruction manual. Devices with embedded processing capability can use
these messages to enable and accept unsolicited binary SER messages from
the SEL-387.
SEL relays and communications processors have two separate data streams
that share the same serial port.
➤ The normal serial interface consists of ASCII character
commands and reports that are intelligible to people using a
terminal or terminal emulation package.
➤ The binary data streams can interrupt the ASCII data stream to
obtain information and then allow the ASCII data stream to
continue.
This mechanism allows use of a single communications channel for ASCII
communications (e.g., transmission of a long event report) interleaved with
short bursts of binary data to support fast acquisition of metering or SER data.
To exploit this feature, the device at the other end of the link requires software
that uses the separate data streams. A device that does not interleave the data
streams can also access the binary commands and ASCII commands.
Recommended Message Usage
Use the following sequence of commands to enable unsolicited binary SER
messaging in the SEL-387:
Step 1. On initial connection send the SNS command to retrieve and
store the ASCII names for the digital I/O points assigned to
trigger SER records. The order of the ASCII names matches the
point indices in the unsolicited binary SER messages.
a. Send the “Enable Unsolicited Data Transfer” message
to enable the SEL-387 to transmit unsolicited binary
SER messages.
Step 2. When SER records are triggered in theSEL-387, the relay
responds with an unsolicited binary SER message. If this
message has a valid checksum, it must be acknowledged by
sending an acknowledge message with the same response
number as that contained in the original message. The relay
NOTE: The SEL-387-0 Relay does
not include this feature.
NOTE: Make Sequential Events
Recorder (SER) Settings With Care
The relay triggers a row in the
Sequential Events Recorder (SER)
event report for any change of state in
any one of the elements listed in the
SER1, SER2, SER3, or SER4 trigger
settings. Nonvolatile memory stores
the latest 512 rows of the SER event
report so they can be retained during
power loss. The nonvolatile memory
stores a finite number of "writes."
Exceeding the limit can result in an
EEPROM self-test failure. An average of 1
state change every 3 minutes can be made
for a 25-year relay service life.
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