7.5
Date Code 20090730 Instruction Manual SEL-734 Meter
Time-Synchronized Measurements
Synchrophasor Measurements
Setup
Unsolicited Fast Messaging is an open SEL binary communications protocol.
To decipher and use the data in the Fast Messages, you must parse the data
with a software program, such as Microsoft
®
Excel with Visual Basic
®
for
Applications or LabView
®
, that is capable of handling communications and
32-bit floating-point number conversion. Table 7.3 provides a complete
description of the Fast Message packet.
The application of the SEL-734 using unsolicited Fast Messaging requires
consideration of a few issues. First, you must decide what data are required for
the application. Second, you must decide how often messages must be
transmitted to satisfy the application requirements. Last, you must evaluate the
communications channels that will transfer the Unsolicited Fast Messages
from the meter to the PC or data concentrator. You must verify that the
communications medium can handle the quantity of data and the frequency of
the messages. Once these questions are answered, you can adjust the serial
port setting to the meter and send the enable message to start receiving
synchrophasor data.
Determine the Data Required
The SEL-734 can provide either positive-sequence voltage, three-phase and
positive-sequence voltages, or three phases of voltage, three phases of current,
and positive-sequence voltage and current. Use the PMDATA port setting to
select the data for synchrophasor Fast Message transmission. See Tab le 7.2 for
details.
In addition to the synchrophasor data, sixteen digital values can be sent in the
Fast Message. The least significant bit contains PMDOK. Next is TSOK. The
next 14 bits are SV03 through SV16.
The frequency data in the Fast Message is based on the Synchrophasor phase
angle when the frequency is in range Fnom ± 5 Hz. The total frequency range
that can be reported is 35 Hz to 75 Hz.
Assign Identification Addresses to Each Meter
The power system can benefit the most from the application of
synchrophasors when data are retrieved from multiple locations
simultaneously. You must be able to discern which meter is sending which
data. The PMADDR port setting provides a four-byte identification tag in
each message packet. Use the PMADDR setting to identify synchrophasor
data from specific locations on the transmission system.
Table 7.2 PMDATA Setting for Synchrophasor Fast Message Data Selection
(Form 9 Meter)
PMDATA Setting Data Size of Packet in Bytes
V1 V1 40
V VA, VB, VC, V1 64
A VA, VB, VC, V1, IA, IB, IC, I1 96
Courtesy of NationalSwitchgear.com
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