I.17
Date Code 20170927 Instruction Manual SEL-751 Relay
Synchrophasors
IEEE C37.118 PMU Setting Example
The PMU data collection requirements call for the following data, collected at
10 messages per second:
➤ Frequency
➤ Positive-sequence voltage from the bus in each substation
➤ Three-phase, positive-sequence, and neutral current for each line
➤ Indication when the breaker is open
➤ Indication when the voltage or frequency information is
unusable
The utility is able to meet the requirements with the SEL-751 for each line, an
SEL-2407 Satellite-Synchronized Clock, and an SEL-3373 Phasor Data
Concentrator in each substation.
This example covers the PMU settings in the SEL-751 Relays. Some system
details:
➤ The nominal frequency is 60 Hz.
➤ The bus PTs and wiring have a phase error of 4.20 degrees
(lagging) at 60 Hz.
➤ The breaker CTs and wiring have a phase error of 3.50 degrees
(lagging) at 60 Hz.
➤ The neutral CTs and wiring have a phase error of 3.50 degrees
(lagging) at 60 Hz.
➤ The synchrophasor data use port 3, and the maximum baud
allowed is 19200.
➤ The system designer specifies integer numeric representation
for the synchrophasor data, and rectangular coordinates.
➤ The system designer specifies integer numeric representation
for the frequency data.
➤ The system designer specifies C37.118 synchrophasor
response, because the data are being used for system
monitoring.
The protection settings are not shown.
The protection engineer performs a bandwidth check, using Ta ble I.10, and
determines the necessary message size. The system requirements, in order of
appearance in Table I.10, are as follows:
➤ 6 Synchrophasors, in integer representation
➤ Integer representation for the frequency data
➤ 3 digital status bits, which require one status word
The message size is 18 + 6 • 4 + 2 • 2 + 1 • 2 = 48 bytes. Using Table I.11, the
engineer verifies that the port baud of 9600 is adequate for the message, at 10
messages per second.
The Protection SEL
OGIC Variables SV14, SV15, and SV16 are used to
transmit the breaker status, loss-of-potential alarm, and frequency
measurement status, respectively. Make the Global settings as shown in
Table I.12.
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