L.10
SEL-351A Relay Instruction Manual Date Code 20080213
SEL Synchrophasors
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When TS_TYPE is set to IRIG, the IRIG message is expected to contain
seconds, minutes, hours, and days. The IRIG source gives no additional
information to the SEL-351A as to its accuracy. The SEL-351A qualifies the
IRIG field to ensure that the time is valid, and then asserts the TIRIG and
TSOK Relay Word bits. The local time, as received by the IRIG source, is
used for all synchrophasor time values. Under these conditions, the specified
SEL-351A synchrophasor accuracy does not include the inaccuracy of the
IRIG time source.
When TS_TYPE is set to IEEE, the IRIG message is expected to conform to
the IEEE C37.118 standard. Note that time sources conforming to
IEEE C37.118 may be marked as IEEE 1344 compliant. The IRIG message
includes a UTC offset, time quality information, a year, and a parity bit. The
SEL-351A qualifies the IRIG field to ensure that the time is valid, checks for a
time quality value better than or equal to ±10 us, and checks for the consistent
parity. If all conditions are met, the TSOK Relay Word bit asserts. As in the
IRIG case, the TIRIG Relay Word bit asserts when the time field has valid
data and does not include additional checks. When the Time Source Type is
set to IEEE, the UTC time value is used in the synchrophasor fast message.
The MET PM command still displays the local time.
Courtesy of NationalSwitchgear.com
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