Schweitzer Engineering Laboratories SEL-351-5, Instruction Manual

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L.14
SEL-351-5, -6, -7 Relay Instruction Manual
Date Code 20070117
SEL Synchrophasors
Communications Bandwidth
Communications Bandwidth
A phasor measurement control unit (PMCU) that is configured to transmit a
single synchrophasor quantity (positive-sequence voltage, for example) at a
message period of one second places little burden on the communications
channel. As more synchrophasors or interleaved protocols are added, some
communications channel restrictions come into play.
The SPEED setting on any serial port set with PROTO = PMU should be set as
high as possible, but no higher than 19200 baud, to allow for the largest
possible number of message period requests to be successful.
The SEL-351 Fast Message synchrophasor format always includes 32 bytes
for the message header and terminal ID, time information, frequency, and
status bits. The selection of synchrophasor data will add to the byte
requirements. Each synchrophasor quantity will add eight bytes to the
message length.
Table L.8 shows the effect that adding synchrophasor
quantities has on the minimum allowed SPEED setting.
The number of interleaved protocols sharing the same physical port will also
impact the minimum allowed SPEED setting.
Table L.8 shows the setting if
the Fast Message Synchrophasor format is the only data stream transmitted;
additional data streams will necessitate a higher SPEED setting.
Table L.8 SEL Fast Message Voltage and Current Selections Based on PHDATAV and PHDATAI
Global
Settings
Number of
Synchrophasor
Magnitude
and Angle Pairs
Transmitted
Synchrophasor Magnitude
and Angle Pairs to Transmit,
and the Transmit Order
Synchrophasor
Data Size
(Bytes)
Minimum Baud Rate
(SPEED Setting)
at One Second Message
Period
PHDATAV = V1
PHDATAI = NA 1 V1 40 1200 Baud
PHDATAV = ALL
PHDATAI = NA 4 VA, VB, VC, V1 64 2400 Baud
PHDATAV = ALL
PHDATAI = ALL 8 VA, VB, VC, V1, IA, IB, IC, I1 96 4800 Baud