Schweitzer Engineering Laboratories, Inc. SEL-787-3, -4 Data Sheet
17
SEL-787 control logic improves integration in the
following ways:
➤ Replaces traditional panel control switches. Elimi-
nate traditional panel control switches with 32 local
bits. Set, clear, or pulse local bits with the front-panel
pushbuttons and display. Program the local bits into
the control scheme with SEL
OGIC control equations.
Use the local bits to perform functions such as a trip
test or a breaker trip/close.
➤ Eliminates RTU-to-relay wiring. Eliminate RTU-to-
relay wiring with 32 remote bits. Set, clear, or pulse
remote bits using serial port commands. Program the
remote bits into the control scheme with SEL
OGIC
control equations. Use remote bits for SCADA-type
control operations such as trip, close, and settings
group selection.
➤ Replaces traditional latching relays. Replace up to
32 traditional latching relays for such functions as
“remote control enable” with latch bits. Program
latch set and latch reset conditions with SEL
OGIC
control equations. Set or reset the nonvolatile latch
bits using optoisolated inputs, remote bits, local bits,
or any programmable logic condition. The latch bits
retain their state when the relay loses power.
➤ Replaces traditional indicating panel lights.
Replace traditional indicating panel lights with 32
programmable displays. Define custom messages
(e.g.,
Breaker Open, Breaker Closed) to report
power system or relay conditions on the front-panel
display. Use advanced SEL
OGIC control equations to
control which messages the relay displays.
➤ Eliminates external timers. Eliminate external tim-
ers for custom protection or control schemes with 32
general purpose SEL
OGIC control equation timers.
Each timer has independent time-delay pickup and
dropout settings. Program each timer input with the
element you want (e.g., time qualify a current ele-
ment). Assign the timer output to trip logic, transfer
trip communications, or other control scheme logic.
➤ Eliminates settings changes. Selectable setting
groups make the SEL-787 ideal for applications
requiring frequent setting changes and for adapting
the protection to changing system conditions. The
relay stores four setting groups. Select the active
setting group by optoisolated input, command, or
other programmable conditions. Use these setting
groups to cover a wide range of protection and con-
trol contingencies. Switching setting groups switches
logic and relay element settings. Program groups for
different operating conditions, such as rental/spare
transformer applications, station maintenance, sea-
sonal operations, emergency contingencies, loading,
source changes, and downstream relay setting
changes.
Fast SER Protocol
SEL Fast Sequential Events Recorder (SER) protocol
provides SER events to an automated data collection
system. SEL Fast SER protocol is available on any rear
serial port. Devices with embedded processing capability
can use these messages to enable and accept unsolicited
binary SER messages from SEL-787 relays. 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 a single communications channel to
be used 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.
SNTP Ethernet-based protocol that provides time synchronization of the relay.
IEC 60870-5-103 Serial communications protocol–international standard for interoperability between intelligent devices in a
substation.
Table 6 Communications Protocols (Sheet 2 of 2)
Type Description
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