2-4 General Description Date Code 20010518
SEL-2020 Instruction Manual
“20” messages for other data collection and control purposes. On SEL IED ports, you can also
have relay operate commands (OPEN, CLOSE) sent automatically.
Receive Messages and Data
The SEL-2020 can receive, buffer, parse, store, and act upon solicited and unsolicited messages
and data.
Unsolicited Messages
Unsolicited messages are strings that are sent to the SEL-2020 without being solicited by the
SEL-2020. These messages include:
SEL-2020 Command Set. The SEL-2020 command set consists of predefined messages, 27 in
all, that the SEL-2020 recognizes, understands, and responds to. You can send these commands,
such as ACCESS, PORT and VIEW, from a dumb terminal or PC using any communication
program that supports ASCII “dumb terminal” emulation. The SEL-2020 command set can be
disabled on a port where user-defined commands are used.
IED Auto-Messages. IEDs may send data to the SEL-2020 without it being requested. These
messages can be buffered and activities can be triggered based on specific messages. SEL relays
send auto-messages to report specific activity or conditions. These include the SEL Event
Report Summary issued through the SEL relay auto port when an event record is stored, the SEL
Status Report issued to report a warning or failure, and the SEL Group Switch Report issued
when a change in group settings occurs on a relay with multiple groups.
User-Defined Commands. You can define commands using the SET U command procedure.
Receipt of one of these commands sets a command element that can be used in a SEL
OGIC
Control Equation to initiate action defined in an associated message string. You can set the
SEL-2020 to use these commands on IED ports to watch for unsolicited messages or on Master
ports to supplement or replace the standard SEL-2020 command set. Use the SET U command to
create User-Defined commands. SET U can also be used to instruct the SEL-2020 to watch for
one, or more, of the standard SEL relay auto-messages. (See Section 6: Settings.)
Modbus Protocol. You can select Ports 12, 14, and 16 of an SEL-2020 as Modbus ports. The
network master (receiver) can access the database of all SEL-2020 ports through a Modbus port.
DNP Protocol. The SEL-2020 supports Distribution Network Protocol (DNP) V3.00 Level 2 on
Port 16. It can be used for data access and for control.
Solicited Messages and Data
A message received in response to an SEL-2020 automatic message is called a solicited message.
The SEL-2020 can recognize a solicited message response in two ways:
“20” Message Response. The “20” message responses are automatically parsed based on the
SEL-2020’s knowledge of the data format. The SEL-2020 uses these messages with SEL relays
to collect relay data such as meter, target, event, and history. Meter and target data are
transferred from the SEL relay to the SEL-2020 in binary format if the relay has Fast Meter
capabilities.
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