Date Code 20011026
M
IRRORED
B
ITS
Communications
H-5
SEL-321/321-1 Instruction Manual
Synchronization
When a node detects a communications error, it deasserts ROK and transmits an attention
message, which includes its TX_ID setting.
When a node receives an attention message, it checks to see if its own TX_ID is included.
If its own TX_ID is included and at least one other TX_ID is included, the node discards the
attention message and transmits data.
If its own TX_ID is not included, the node deasserts ROK, includes its TX_ID in the attention
message, and transmits the new attention message.
If its own TX_ID is the only TX_ID included, the node assumes the message is corrupted unless
the loop back mode has been enabled. If loop back is not enabled, the node deasserts ROK and
transmits the attention message with its TX_ID included. If loop back is enabled, the node
discards the attention message and transmits data.
Note:
In summary, when a node detects an error, it transmits attention until it receives an
attention with its own TX_ID included. If three or four relays are connected in a ring
topology, then the attention message will go all the way around the loop, and will
eventually be received by the originating node. It will then be discarded, and data
transmission will resume. This method of synchronization allows the nodes to reliably
determine which character is the first character of the message. It also forces a
mis-synchronized relay to become re-synchronized. This method takes down the entire
loop for a receive error at any node in the loop, an exchange of availability for security.
Loopback Testing
Physically loopback the M
IRRORED
B
ITS
communication channel external to the relay. Then use
the LOOP command to enable loopback testing.
While in loopback mode, ROK is deasserted, and the relay element LBOK will assert and
deassert based on the ROK checks listed above.
The TAR command, front panel targets, and/or the COMM command may be used to monitor the
loopback test.
Refer to the SEL-321 or SEL-351 manuals for additional information on these commands.
Channel Monitoring
Based on the results of data checks described above, the relay will collect information regarding
the 255 most recent communications errors. Each record will contain at least the following
fields:
·
Dropout Time/Date
·
Pickup Time/Date
·
Time elapsed during dropout
·
Reason for dropout (See Message Decoding and Integrity Checks)
Содержание SEL-321
Страница 4: ......
Страница 10: ......
Страница 12: ......
Страница 78: ...2 54 Specifications Date Code 20011026 SEL 321 321 1 Instruction Manual Figure 2 4 Logic Symbol Legend ...
Страница 87: ...Date Code 20011026 Specifications 2 63 SEL 321 321 1 Instruction Manual Figure 2 21 Load Encroachment Logic ...
Страница 94: ...2 70 Specifications Date Code 20011026 SEL 321 321 1 Instruction Manual Figure 2 29 Voltage Element Logic ...
Страница 162: ......
Страница 171: ...Date Code 20011026 Event Reporting 4 9 SEL 321 321 1 Instruction Manual ...
Страница 263: ...SEL DIRECTION AND POLARITY CHECK FORM ...
Страница 264: ......
Страница 265: ...SEL DIRECTION AND POLARITY CHECK FORM ...
Страница 266: ......
Страница 270: ......
Страница 358: ......
Страница 360: ......
Страница 362: ......
Страница 366: ......
Страница 370: ......
Страница 390: ......