7.3
Date Code 20090730 Instruction Manual SEL-734 Meter
Time-Synchronized Measurements
Synchrophasor Measurements
Synchrophasor Measurements
Introduction
Synchronized phasor measurement provides power system data referenced to
the same instant in time from multiple SEL-734 meters at different locations
on a power system. This feature reduces time for system state estimation,
which results in improved system optimization and increased line loading
with fewer safety margin requirements.
This subsection details the retrieval of synchrophasor (synchronized phasor
measurement) data from the SEL-734. You can access data as fast as 20
samples per second to monitor the power system in real time.
System Requirements
Basic Connections
Each SEL-734 must be connected to a timing source, such as a global
positioning system (GPS) receiver, that is accurate to within ±0.50 μs of
Coordinated Universal Time (UTC). The clock source must be able to provide
a demodulated IRIG-B signal. Use the 2-pin phoenix connector labeled
IRIG-B to connect the SEL-734 to this source.
Specifications
The SEL-734 Meter Word contains a “Timing Source OK” element (TSOK)
that asserts when the IRIG-B signal has been present for a sufficient duration
to allow the SEL-734 to obtain proper internal time lock. A second Meter
Word, PMDOK, asserts when TSOK has asserted and the synchronized
phasor algorithm is at the specified accuracy. When PMDOK asserts, the
SEL-734 provides synchronized measurement accuracy with level 0 of IEEE
C37.118-2005. Depending on the application, loss of the time source signal,
with corresponding PMDOK deassertion, can cause the accuracy of the
synchronized data to be outside specifications or the meter to respond with an
abort message. PMDOK also deasserts if the meter is disabled.
Settings
You must enable synchronized phasor measurements by setting EPMU := Y
before the SEL-734 reports synchrophasor data (see SET G Command on
page SET.5). See Ta bl e 7 . 1 for a list of all required synchrophasor settings.
When EPMU := Y, the meter prompts for the synchrophasor precision time
source type through the TSTYPE setting. The TSTYPE setting accepts either
an IRIG or IEEE time source input. When TSTYPE = IRIG, the SEL-734
expects local time from the IRIG time source. When TSTYPE = IEEE, the
SEL-734 expects the IRIG message to contain a UTC offset, encoded
according to the IEEE C37.118-2005 standard.
The port settings for the SEL-734 contain PMDATA and PMADDR settings
specific to the synchrophasor application. The PMDATA setting provides you
the choice of analog quantities that the SEL-734 transmits in the
synchrophasor message (see Table 7.1).
The PMADDR setting assigns a unique address to synchrophasor data that
identifies each SEL-734.
Courtesy of NationalSwitchgear.com
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