GE Multilin
M60 Motor Protection System
5-93
5 SETTINGS
5.2 PRODUCT SETUP
5
b) CRC ALARM CH1(2)
PATH: SETTINGS
PRODUCT SETUP
DIRECT I/O
CRC ALARM CH1(2)
The M60 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
set-
ting, both the counters reset and the monitoring process is restarted.
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 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 monitor-
ing time interval will shorten. This should be taken 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
should be set to 10
60
1 = 600.
•
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 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
MESSAGE
CRC ALARM CH1
MESSAGE COUNT: 600
Range: 100 to 10000 in steps of 1
MESSAGE
CRC ALARM CH1
THRESHOLD: 10
Range: 1 to 1000 in steps of 1
MESSAGE
CRC ALARM CH1
EVENTS: Disabled
Range: Enabled, Disabled
Summary of Contents for M60 UR Series
Page 10: ...x M60 Motor Protection System GE Multilin TABLE OF CONTENTS ...
Page 128: ...4 30 M60 Motor Protection System GE Multilin 4 3 FACEPLATE INTERFACE 4 HUMAN INTERFACES 4 ...
Page 410: ...5 282 M60 Motor Protection System GE Multilin 5 10 TESTING 5 SETTINGS 5 ...
Page 440: ...6 30 M60 Motor Protection System GE Multilin 6 5 PRODUCT INFORMATION 6 ACTUAL VALUES 6 ...
Page 452: ...7 12 M60 Motor Protection System GE Multilin 7 2 TARGETS 7 COMMANDS AND TARGETS 7 ...
Page 462: ...9 8 M60 Motor Protection System GE Multilin 9 2 BATTERIES 9 MAINTENANCE 9 ...
Page 474: ...A 12 M60 Motor Protection System GE Multilin A 1 PARAMETER LISTS APPENDIX A A ...
Page 584: ...B 110 M60 Motor Protection System GE Multilin B 4 MEMORY MAPPING APPENDIX B B ...
Page 614: ...C 30 M60 Motor Protection System GE Multilin C 7 LOGICAL NODES APPENDIX C C ...
Page 630: ...E 10 M60 Motor Protection System GE Multilin E 1 IEC 60870 5 104 PROTOCOL APPENDIX E E ...
Page 642: ...F 12 M60 Motor Protection System GE Multilin F 2 DNP POINT LISTS APPENDIX F F ...
Page 644: ...G 2 M60 Motor Protection System GE Multilin G 1 RADIUS SERVER CONFIGURATION APPENDIX G G ...
Page 652: ...H 8 M60 Motor Protection System GE Multilin H 3 WARRANTY APPENDIX H H ...
Page 662: ...x M60 Motor Protection System GE Multilin INDEX ...