Sel 411L - Figure 3.197 Synchronization Method Logic (P-Th Channel)

P.3.289
Date Code 20151029 Protection Manual SEL-411L Relay
Protection Functions
87L Channel Synchronization Logic and Status
synchronization. This breaks the ping-pong time-stamp exchange sequence
and prevents the local relay from calculating the clock offset with respect to
the remote relay.
Figure 3.197 Synchronization Method Logic (p-th Channel)
If the channel-based synchronization method is in effect (87CHpCS asserted),
the averaged clock offset measurement (87CHpTOFF) is used for alignment
of 87L data the relay receives on the p-th channel. In channel-based
synchronization, the External Time Lock Relay Word bit (ETLp) is
suppressed. Therefore, ETL will not assert when the Port 87 setting
E87CHpSN = C, even if a valid time source is connected to the relay.
If the time based-based synchronization method is in effect (87CHpTS
asserted), the relay uses the value of 0 ms as the clock offset for alignment of
87L data the relay receives on the p-th channel.
If neither method is in effect (87CHpNS asserted) for any of the required
channels (channels with 87CHpRQ asserted), the relay can use no remote data
and ceases to act as a master.
The relay monitors synchronization quality with the intent of providing you
visibility via selected Relay Word bits. It then dynamically adjusts 87L
settings if synchronization is degraded or when the time fallback logic
dynamically changes the synchronization method.
As Figure 3.198 shows, a given active channel (87CHpAC asserted) can be in
a high-quality synchronization state (87CHpHS) or low-quality
synchronization state (87CHpLS asserted).
In reference to Figure 3.198 when the synchronization mode changes, the
relay intentionally declares lower synchronization quality for a half second as
a precautionary measure. Also, when the relay uses the channel-based
synchronization method, the accuracy of the clock offset measurement feeds
into the logic of Figure 3.198.
In addition to monitoring synchronization quality for each channel
individually, the relay monitors the synchronization quality for the 87L
scheme (see Figure 3.199).
Settings
E87CH = 2E, 3E, 4E
E87CH = 2SS, 2SD, 3SS, 3SM
87CHpSN = T
Settings
87TOK
87CHpNS
87CHpCS
87CHpTS
To remote
relays as ETL
Received on the
p-th channel
E87CHpSN = C
87CHpFC
Relay
Word Bit
ETLp
Relay
Word Bit
87CHpCL
87CHpCH
Relay
Word Bits
Relay
Word Bits