Date Code 20150130 Instruction Manual SEL-787 Relay
Appendix I
MIRRORED BITS Communications
Instruction Manual
Overview
MIRRORED BITS
®
communications is a direct relay-to-relay communications
protocol that allows IEDs to exchange information quickly, securely, and with
minimal expense. Use M
IRRORED BITS for functions such as remote control
and remote sensing. The SEL-787 Transformer Protection Relay supports two
M
IRRORED BITS communications channels, designated A and B. Use the port
setting PROTO to assign one of the M
IRRORED BITS communications
channels to a serial port; PROTO:=MBA for M
IRRORED BITS
communications Channel A or PROTO:=MBB for M
IRRORED BITS
communications Channel B. M
IRRORED BITS are either Transmit MIRRORED
B
ITS (TMB) or Received MIRRORED BITS (RMB). Transmit MIRRORED BITS
include TMB1A–TMB8A (channel A) and TMB1B–TMB8B (channel B).
The last letter (A or B) designates with which channel the bits are associated.
Received bits include RMB1A–RMB8A and RMB1B–RMB8B. Control the
transmit M
IRRORED BITS in SELOGIC
®
control equations. Use the received
M
IRRORED BITS as arguments in SELOGIC control equations. The channel
status bits are ROKA, RBADA, CBADA, LBOKA, ROKB, RBADB,
CBADB, and LBOKB. You can also use these channel status bits as
arguments in SEL
OGIC control equations. Use the COM command (see
Section 7: Communications) for additional channel status information.
Because of different applications, the SEL product range supports several
variations of the M
IRRORED BITS communications protocol. Through port
settings, you can set the SEL-787 for compatible operation with SEL-300
series devices, SEL-2505 Remote I/O Modules, and SEL-2100 Logic
Processors. When communicating with an SEL-400 series relay, be sure to set
the transmission mode setting in the SEL-400 series relay to paced
transmission (TXMODE: = P).
Operation
Message
Transmission
In the SEL-787, the MIRRORED BITS transmission rate is a function of both the
baud rate and the power system cycle. At baud rates below 9600, the SEL-787
transmits M
IRRORED BITS as fast as possible for the given baud. At rates at
and above 9600 baud the SEL-787 self-paces, using a technique similar to the
SEL-400 series pacing mode. There are no settings to enable or disable the
self-pacing mode; the SEL-787 automatically enters the self-pacing mode at
baud rates of 9600, 19200, and 38400. Table I.1 shows the transmission rates
of the M
IRRORED BITS messages at different baud.
IMPORTANT: Be sure to configure
the port before connecting to a
M
IRRORED BITS device. If you connect
an unconfigured port to a M
IRRORED
B
ITS device, the device will appear to
be locked up.
NOTE: Complete all of the port
settings for a port that you use for
M
IRRORED BITS communications before
you connect an external M
IRRORED BITS
communications device. If you
connect a M
IRRORED BITS
communications device to a port that
is not set for M
IRRORED BITS
communications operation, the port
will be continuously busy.
To Next Page
Loading...
