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Messages are predefined responses that may include data, responses to special-purpose user-
defined commands, and automatic messages that you have defined in settings and that are trig-
gered by SEL
OGIC control equations. You can use relay automatic messages to initiate data
collection by setting the SEL-2020 to collect and store data when an unsolicited message is
received. For example, receiving a summary event report could trigger the SEL-2020 to send the
EVENT command back to the relay. The relay would respond with the long event report, and the
SEL-2020 could then save it. You can store the data in volatile RAM or in the optional
nonvolatile archive memory.
Data Area With Automatic Database
The Data Area is divided into regions of volatile (RAM) and nonvolatile memory. The SEL-2020
stores settings in nonvolatile memory. The SEL-2020 is unique in its ability to receive, parse,
store, and distribute data. The SEL-2020 automatically parses data from SEL relays, and has
several parsing options for data from other devices. Additional nonvolatile archive memory is an
option you can use for long-term data storage.
SEL
OGIC Control Equations Processor
The SEL
OGIC Control Equations Processor executes Boolean equations that you write to trigger
transmission of messages. The Boolean values in the equations can be logic bits from the Data
Area or comparisons against the present time. You can program the SEL-2020 to recognize user-
defined commands and to set a bit in the Data Area when it receives one of these commands. The
SEL
OGIC Control Equations Processor can then use this bit to initiate another operation, such as
collecting data or transmitting a message. The SEL
OGIC Control Equations Processor also
controls the optional I/O.
Arithmetic building blocks include addition, subtraction, multiplication, and division.
Time Processor
The Time Processor keeps the date and time, reads IRIG-B time input (if it is present), and
broadcasts demodulated IRIG-B time code to all rear-panel serial ports. It also time-tags data
stored in the Data Area and supplies time and day of the week input to the SEL
OGIC Control
Equations Processor.
Optional I/O
If the optional I/O is installed, the inputs and outputs operate with the Data Area and the
SEL
OGIC Control Equations Processor. Optoisolated inputs feed directly into the Data Area as
logic bits, which you can view using SEL-2020 commands. You can program SEL
OGIC control
equations to use the bits. The SEL
OGIC Control Equations Processor controls the output contacts
on the I/O board. These output contacts can be programmed to operate based on Data Area bits
or time comparisons. This powerful capability lets you build adaptive relay schemes, automate
responses to alarms, and directly control power apparatus.
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