Date Code 20081022
Instruction Manual
SEL-787 Relay
Appendix H
Synchrophasors
Instructi on Manual
Introduction
The SEL-787 Transformer Protection Relay provides Phasor Measurement
Control Unit (PMCU) capabilities when connected to an IRIG-B time source
with an accuracy of ±10 µs or better. Synchrophasor data are available via the
MET PM
ASCII command and the C37.118 Protocol.
Synchrophasor measurement refers to the concept of providing measurements
taken on a synchronized schedule at precise instants in time. A high-accuracy
clock, commonly called a Global Positioning System (GPS) receiver such as
the SEL-2407 Satellite-Synchronized Clock, makes synchrophasor
measurement possible.
The availability of an accurate time reference over a large geographic area
allows multiple devices, such as SEL-787 relays, to synchronize the gathering
of power system data. The accurate clock allows precise event report
triggering and other off-line analysis functions.
The SEL-787 Global settings class contains the synchrophasor settings,
including the choice of transmitted synchrophasor data set. The Port settings
class selects which serial port(s) can be used for synchrophasor protocol use.
See
Settings for Synchrophasors on page H.4
The SEL-787 timekeeping function generates status Relay Word bits and
time-quality information that is important for synchrophasor measurement.
Some protection SEL
OGIC
variables, and programmable digital trigger
information is also added to the Relay Word bits for synchrophasors.See
Synchrophasor Relay Word Bits on page H.9
.
When synchrophasor measurement is enabled, the SEL-787 creates the
synchrophasor data set at a user-defined rate. Synchrophasor data are available
in ASCII format over a serial port set to PROTO = SEL. See
Synchrophasors Using the MET PM Command on page H.10
.
The value of synchrophasor data increases greatly when the data can be shared
over a communications network in real time. A synchrophasor protocol is
available in the SEL-787 that allows for a centralized device to collect data
efficiently from several phasor measurement units (PMUs). Some possible
uses of a system-wide synchrophasor system include the following:
➤
Power-system state measurement
➤
Wide-area network protection and control schemes
➤
Small-signal analysis
➤
Power-system disturbance analysis
Summary of Contents for SEL-787
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