CHAPTER 6: COMMUNICATIONS DIRECT INPUTS AND OUTPUTS
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL 153
CRC Alarm Count
Range: 100 to 10000 in steps of 1
Default: 600
When the total message counter reaches the user-defined maximum specified by this
setting, both the counters reset and the monitoring process is restarted.
To monitor communications integrity, the D90
Plus
sends one message per second (at
64 kbps) or two messages per second (128 kbps) even if there is no change in the direct
outputs. For example, setting the
CRC Alarm Count to “10000” corresponds to a time
window of about 160 minutes at 64 kbps and 80 minutes at 128 kbps. If the messages
are sent faster as a result of direct outputs activity, the monitoring time interval
shortens. Take this into account when determining this setting. For example, if the
requirement is a maximum monitoring time interval of 10 minutes at 64 kbps, then the
setting is 10 × 60 × 1 = 600.
CRC Alarm Threshold
Range: 1 to 1000 in steps of 1
Default: 10
When the failed CRC counter reaches the user-defined level specified by this setting
within the user-defined message count specified by
CRC Alarm Count, the DIR IO CH1 CRC
ALARM or DIR IO CH2 CRC ALARM FlexLogic operand is set. The operand can be configured
to drive an output contact, annunciator alarm, or selected communication-based
output. Program latching and acknowledging conditions, if required, accordingly in the
annunciator settings.
CRC Alarm Events
Range: Enabled, Disabled
Default: Disabled
This setting enables and disables the logging of CRC alarm events in the sequence of
events recorder.
Message Alarm Function
Range: Enabled, Disabled
Default: Disabled
The D90
Plus
checks integrity of the direct input/output communication ring by counting
unreturned messages. In the ring configuration, all messages originating at a given
device are to return within a pre-defined period of time. The unreturned messages alarm
function is available for monitoring the integrity of the communication ring by tracking
the rate of unreturned messages. This function counts all outgoing messages and a
separate counter adds the messages have failed to return.
The unreturned messages alarm function is available on a per-channel basis and is
active only in the ring configuration. The total number of unreturned input/output
messages is available as an actual value.
Message Alarm Count
Range: 100 to 10000 in steps of 1
Default: 600
When the total message counter reaches the user-defined maximum specified by this
setting, both the counters reset and the monitoring process restarts.
Message Alarm Threshold
Range: 1 to 1000 in steps of 1
Default: 10
When the unreturned messages counter reaches the user-definable level specified by
this setting and within the user-defined message count specified by
Channel 1 Msg
Alarm Count
, the DIR IO CH1 UNRET ALM FlexLogic operand is set. The operand needs to be
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