3.7.1
SNTP
NOTICE!
Important pre-condition: The device needs to have access to an SNTP server via the
connected network. This server preferably should be installed locally.
Principle – General Use
SNTP is a standard protocol for time synchronization via a network. At minimum, one
SNTP server has to be integrated into the network. The device can be configured for one
or two connected SNTP servers.
The device's system time will be synchronized by the connected SNTP server 1 to 4 times
per minute. In turn, the SNTP server synchronizes its time via NTP with other NTP servers.
This is the normal case. Alternatively it can receive its time via GPS, radio controlled
clock, or the like.
E_F48
GPS Satellite Signal (optional)
GPS Connection (optional)
NTP-Server
(option)
SNTP-Server
Protective Relay
TCP/IP
TCP/IP
NTP-Protocol
SNTP-Protocol
Operational
Ph OC Trip
Gnd OC Trip
Ph Inst Trip
Gnd Inst Trip
Pickup
Bkr Failure
Maint. Mode
Info
Ack/Rst
Ok
CTRL
Accuracy
The accuracy of the SNTP server used and the accuracy of its reference clock influences
the accuracy of the protection relay's clock. Further information about accuracy:
With each transmitted time information, the SNTP server sends information about its
accuracy:
• Stratum: The stratum gives information on how close the SNTP server within the
cluster is to other NTP servers that are connected to an atomic clock. (If the server's
“stratum” has been set manually, it is not an indication of its quality or reliability.)
• Precision: This is the accuracy, the SNTP server provides the system time.
Also the performance (traffic and data package transmission time) of the connected
network has an influence on the accuracy of the time synchronization. A locally installed
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EMR-3MP0
3 Communication Protocols
3.7 Time Synchronization