Schweitzer Engineering SEL-351P, Быстрый старт

Страница: 666 / 674

Date Code 990430 M
IRRORED
B
ITS
I-1
SEL-351P Manual Técnico
APPENDIX I: M
IRRORED
B
ITS
™
O
VERVIEW
M
IRRORED
B
ITS
is a direct relay-to-relay communications protocol which allows protective
relays to exchange information quickly and securely, and with minimal expense. The
information exchanged can facilitate remote control, remote sensing, or communications-assisted
protection schemes such as POTT, DCB, etc. The SEL-351P Recloser Control supports two
M
IRRORED
B
ITS
channels, differentiated by the channel specifiers A and B. Bits transmitted are
called TMB1x through TMB8x, where x is the channel specifier (e.g., A or B), and are controlled
by the corresponding SEL
OGIC
®
Control Equations. Bits received are called RMB1x through
RMB8x and are usable as inputs to any SEL
OGIC
Control Equations. Channel status bits are
called ROKx, RBADx, CBADx and LBOKx and are also usable as inputs to any SEL
OGIC
Control Equations. Further channel status information is available via the COM command.
O
PERATION
Message Transmission
All messages are transmitted without idle bits between characters. Idle bits are allowed between
messages.
•
At 4800 baud, one message is transmitted each 1/2 power system cycle.
•
At 9600 baud, one message is transmitted each 1/4 power system cycle.
•
At 19200 and 38400 baud, one message is transmitted each 1/8 power system cycle for
the SEL-321 and 1/4 power system cycle for the SEL-351 and the SEL-351P.
Message Decoding and Integrity Checks
The relay will deassert a user-accessible flag per channel (hereafter called ROKx) upon failing
any of the following received-data checks:
•
Parity, framing, or overrun errors.
•
Receive data redundancy error.
•
Receive message identification error.
•
No message received in the time three messages have been sent.
While ROKx is not asserted, the relay will:
1. Prevent new data from being transferred to the pickup dropout security counters
described later. Instead, the relay will send one of the following user selectable
values (hereafter called default values) to the security counter inputs:
•
1
•
0
•
The last valid value
The user will be allowed to select one of the default values for each RMB.