GE D30 Instruction Manual page 147

5 SETTINGS
monitoring time interval will shorten. This should be taken into account when determining the
setting. For example, if the requirement is a maximum monitoring time interval of 10 minutes at 64 kbps, then
COUNT
the
CRC ALARM CH1 MESSAGE COUNT
• Correlation of Failed CRC and Bit Error Rate (BER): The CRC check may fail if one or more bits in a packet are cor-
rupted. Therefore, an exact correlation between the CRC fail rate and the BER is not possible. Under certain assump-
tions an approximation can be made as follows. A direct input/output packet containing 20 bytes results in 160 bits of
data being sent and therefore, a transmission of 63 packets is equivalent to 10,000 bits. A BER of 10
error for every 10,000 bits sent/received. Assuming the best case of only 1 bit error in a failed packet, having 1 failed
packet for every 63 received is about equal to a BER of 10
c) UNRETURNED MESSAGES ALARM CH1(2)
PATH: SETTINGS PRODUCT SETUP
UNRETURNED
MESSAGES ALARM CH1
MESSAGE
MESSAGE
MESSAGE
The D30 checks integrity of the direct input/output communication ring by counting unreturned messages. In the ring con-
figuration, all messages originating at a given device should 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 unre-
turned messages. This function counts all the outgoing messages and a separate counter adds the messages have failed
to return. When the unreturned messages counter reaches the user-definable level specified by the
setting and within the user-defined message count
CH1 THRESHOLD
FlexLogic™ operand is set.
ALM
When the total message counter reaches the user-defined maximum specified by the
setting, both the counters reset and the monitoring process is restarted.
COUNT
The operand shall be configured to drive an output contact, user-programmable LED, or selected communication-based
output. Latching and acknowledging conditions, if required, should be programmed accordingly.
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 the
UNRETURNED MSG COUNT CH1(2)
GE Multilin
should be set to 10 × 60 × 1 = 600.
–4
.
DIRECT I/O UNRETURNED MESSAGES ALARM CH1(2)
UNRET MSGS ALARM CH1
FUNCTION: Disabled
UNRET MSGS ALARM CH1
MESSAGE COUNT: 600
UNRET MSGS ALARM CH1
THRESHOLD: 10
UNRET MSGS ALARM CH1
EVENTS: Disabled
actual value.
D30 Line Distance Relay
CRC ALARM CH1 MESSAGE
Range: Enabled, Disabled
Range: 100 to 10000 in steps of 1
Range: 1 to 1000 in steps of 1
Range: Enabled, Disabled
UNRET MSGS ALARM CH1 COUNT
UNRET MSGS ALARM CH1 MESSAGE
ACTUAL VALUES STATUS
5.2 PRODUCT SETUP
–4
implies 1 bit
5
UNRET MSGS ALARM
, the
DIR IO CH1 UNRET
DIRECT INPUTS
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