17.17
Date Code 20171006 Instruction Manual SEL-400 Series Relays
IEC 61850 Communication
Sampled Values
Time Synchronization
SmpCnt is a representation of the time stamp, which is encoded in each SV mes-
sage. If SV messages from multiple merging units are used for an application, the
smpCnt from these merging units must represent the same time instance to cor-
rectly align the data. High-accuracy time synchronization is critical. SEL-400
series relays can be synchronized with high-quality IRIG-B or high-quality Preci-
sion Time Protocol (PTP). The quality of smpCnt at the time the sample was
taken is indicated by the SmpSynch value included in each SV message. When a
merging unit is not time synchronized to any time source, its sample time error is
unknown. Without time synchronization, the relay sets the smpSynch to 0. When
the merging unit is synchronized to a high-quality local time source (TLOCAL =
1), the smpSynch is set to 1. When the merging unit is synchronized to a high-
quality global time source (TGLOBAL = 1), the smpSynch is set to 2. TLOCAL
and TGLOBAL are indicators of the time-synchronization source. See
Section 11: Time and Date Management for information about TLOCAL and
TGLOBAL.
SEL merging units use the information in Table 17.7 and Table 17.8 to determine
the quality of sample timing and the smpSynch values. See Table 1 7.7 and
Table 17.8 for smpSynch values.
When high-quality IRIG-B is the current time source (CUR_SRC = BNC_IRIG
or CUR_SRC = SER_IRIG):
When high-quality PTP is the current time source (CUR_SRC = PTP):
SV Subscription
An SEL SV relay can receive one or more SV streams from one or more merging
units. SEL SV relays only support receiving 9-2LE-compliant SV messages.
Once messages are received, samples are buffered to ensure that samples used to
calculate protection elements are from the same time. The SV message attribute,
smpCnt, is used to check and align samples. SV messages can be published at
different frequencies based on the nominal frequency. The SEL SV relay nominal
frequency setting must match the merging unit nominal frequency.
Table 17.7 Mechanism of Determining smpSynch Values With an IRIG-B Time
Source
Time Synchronization Status smpSynch Value
TGLOBAL = 1 2
TLOCAL = 1 1
TGLOBAL = 0
TLOCAL = 0
0
Table 17.8 Mechanism of Determining smpSynch Values With a PTP Time
Source
Profile MU Sync State smpSynch Value
Power System or Default Profile TGLOBAL = 1 2
Power System Profile TLOCAL = 1 GMID
a
a
Grand Master ID
Default Profile TLOCAL = 1 1
Power System or Default Profile TGLOBAL = 0
TLOCAL = 0
0
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