SEL-787-2, -3, -4 Data Sheet
Schweitzer Engineering Laboratories, Inc.
22
Apply an SEL communications processor as the hub of a
star network with a point-to-point fiber or copper
connection between the hub and the SEL-787
(see
).
The communications processor supports external
communications links, including the public switched
telephone network, for engineering access to dial-out
alerts and private line connections of the SCADA
system.
Figure 31
Example Communications System
SEL manufactures a variety of standard cables for
connecting this and other relays to a variety of external
devices. Consult your SEL representative for more
information on cable availability.
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
your control scheme with SEL
OGIC
control equa-
tions. Use the local bits to perform functions such as
a trip test or a breaker trip/close.
➤
Eliminates RTU-to-relay wiring with 32 remote
bits.
Set, clear, or pulse remote bits using serial port
commands. Program the remote bits into your con-
trol 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 as
many as 32 traditional latching relays for such func-
tions as remote control enable with latch bits. Pro-
gram latch set and latch reset conditions with
SEL
OGIC
control equations. Set or reset the nonvola-
tile 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 SER protocol provides SER events to an auto-
mated 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 proces-
sors 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 communi-
cations (e.g., transmission of a long event report) inter-
leaved with short bursts of binary data to support fast
acquisition of metering or SER data.
Fast Message Protocol
SEL Fast Message Protocol is a method to input or mod-
ify remote analogs in the SEL-787. These remote ana-
logs can then be used in SEL Math or SEL
OGIC
control
equations. Remote analogs can also be modified via
Modbus, DNP3, and IEC 61850.
Dial-Up ASCII Link
SCADA Link
SEL Communications Processor
ASCII Reports Plus
Interleaved Binary Data
SEL-787
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