Schweitzer Engineering Laboratories SEL-311C - Introduction

G.2
SEL-311C Relay Instruction Manual Date Code 20060320
SEL Synchrophasors
Introduction
Introduction
Synchrophasor measurement refers to the concept of providing measurements
taken on a synchronized schedule at precise instants in time. A high-accuracy
clock, commonly 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-311C relays, to synchronize the
gathering of power system data. The accurate clock allows precise event
report analysis and other off-line analysis functions.
The value of synchrophasor data increases greatly when the data can be shared
over a communications network in real time. 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
The SEL-311C 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 on page G.8.
The SEL-311C timekeeping function generates status Relay Word bits that are
important for synchrophasor measurement. See Synchrophasor Relay Word
Bits on page G.11.
When synchrophasor measurement is enabled, the SEL-311C 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.
Synchrophasor data is collected with an SEL communications processor (i.e.,
SEL-2032) or a dedicated synchrophasor processor.
The SEL Fast Message Synchrophasor protocol is able to share the same
physical port with separate data streams; see Overview on page D.1.
Synchrophasor measurement provides the option to display event report data
aligned to a high-accuracy time source. See Synchrophasor-Level Accuracy in
Event Reports on page 12.7.