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L60 LINE PHASE COMPARISON SYSTEM – INSTRUCTION MANUAL
PRODUCT SETUP
CHAPTER 5: SETTINGS
5
DIRECT OUTPUT DEVICE ID: “2”
DIRECT I/O CH1 RING CONFIGURATION: “Yes”
DIRECT I/O CH2 RING CONFIGURATION: “Yes”
For UR-series IED 3:
DIRECT OUTPUT DEVICE ID: “3”
DIRECT I/O CH1 RING CONFIGURATION: “Yes”
DIRECT I/O CH2 RING CONFIGURATION: “Yes”
In this configuration the following delivery times are expected (at 128 kbps) if both the rings are healthy:
IED 1 to IED 2: 0.2 of power system cycle
IED 1 to IED 3: 0.2 of power system cycle
IED 2 to IED 3: 0.2 of power system cycle
The two communications configurations can be applied to both permissive and blocking schemes. Take speed, reliability,
and cost into account when selecting the required architecture.
5.3.18.2 CRC alarm CH1(2)
SETTINGS
PRODUCT SETUP
DIRECT I/O
CRC ALARM CH1(2)
The L60 checks integrity of the incoming direct input and output messages using a 32-bit CRC. The CRC alarm function is
available for monitoring the communication medium noise by tracking the rate of messages failing the CRC check. The
monitoring function counts all incoming messages, including messages that failed the CRC check. A separate counter
adds up messages that failed the CRC check. When the failed CRC counter reaches the user-defined level specified by the
CRC ALARM CH1 THRESHOLD
setting within the user-defined message count
CRC ALARM 1 CH1 COUNT
, the
DIR IO CH1 CRC ALARM
FlexLogic operand is set.
When the total message counter reaches the user-defined maximum specified by the
CRC ALARM CH1 MESSAGE COUNT
setting, both the counters reset and the monitoring process is restarted.
Configure the operand to drive an output contact, user-programmable LED, or selected communication-based output.
Latching and acknowledging conditions—if required—are programmed accordingly.
The CRC alarm function is available on a per-channel basis. The total number of direct input and output messages that
failed the CRC check is available as the
ACTUAL VALUES
STATUS
DIRECT INPUTS
CRC FAIL COUNT CH1
actual value.
•
Message count and length of the monitoring window
— To monitor communications integrity, the relay sends 1
message per second (at 64 kbps) or 2 messages per second (128 kbps) even if there is no change in the direct outputs.
For example, setting the
CRC ALARM CH1 MESSAGE COUNT
to “10000,” corresponds 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 the
CRC ALARM CH1 MESSAGE COUNT
setting. For example, if the requirement is a maximum monitoring time interval of 10 minutes at 64 kbps, then the
CRC
ALARM CH1 MESSAGE COUNT
is set to 10
×
60
×
1 = 600.
•
Correlation of failed CRC and bit error rate (BER)
— The CRC check can fail if one or more bits in a packet are
corrupted. Therefore, an exact correlation between the CRC fail rate and the BER is not possible. Under certain
assumptions an approximation can be made as follows. A direct input and 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
–4
implies 1 bit error for every 10000 bits sent or 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
–4
.
CRC ALARM CH1
CRC ALARM CH1
FUNCTION: Disabled
Range: Enabled, Disabled
CRC ALARM CH1
MESSAGE COUNT: 600
Range: 100 to 10000 in steps of 1
CRC ALARM CH1
THRESHOLD: 10
Range: 1 to 1000 in steps of 1
CRC ALARM CH1
EVENTS: Disabled
Range: Enabled, Disabled