
Time-Synchronization Procedure
The device was set to external time synchronization (Ethernet NTP) during parameterization. After switching
on or resetting the device, the FAIL bit is first set to 1 (= invalid). The device sends a time request to the NTP
server. After receiving the time information from the NTP server via Ethernet, the FAIL bit is set to 0 (= valid)
and the internal timer (RTC) is updated. The SNTP client repeats the time request to the NTP server cyclically
once every minute.
If the primary NTP server fails (for example, no response to a request twice or one of the criteria at Redundant
NTP server satisfied) and if the secondary NTP server is operational (always polled in parallel), the device
switches to the secondary NTP server. The FAIL bit remains = 0. In this case, the operational indication Primary
NTP Server Error is displayed, see chapter
13 Operational Indications and Operating Parameters
If the secondary NTP server is also invalid, the FAIL bit will be set to 1 after the programmable timer error
indication after has expired, and the Clock Error indication is output.
Redundant NTP Servers
The time synchronization supports a primary and a secondary NTP server. Different IP addresses are set for
both of the NTP servers.
The device cyclically polls both NTP servers once every minute, but during normal operation it is synchronized
by the primary NTP server. The device automatically switches to the secondary NTP server if one of the
following criteria is met:
•
No response from the primary NTP server to 2 successive requests
•
Alarm indication is set in the time information of the primary NTP server
•
Primary NTP server responds with 0
•
Message runtime in the network is > 5 ms
•
Stratum of the primary NTP server is 0 (unknown) or > 5
Switching to the secondary NTP server is prevented if:
•
The secondary server does not provide better time information (see criteria that initiate the switch from
the primary to the secondary NTP server; Secondary NTP Server Error indication was already output)
•
The secondary server has recently been available for less than 10 minutes.
In these cases, the device is not externally synchronized anymore. The device uses the internal clock (on milli-
seconds time basis) and the last valid drift. After the programmable time delay, the device reports Clock Error
(see chapter
13 Operational Indications and Operating Parameters
).
Switching Back from the Secondary to the Primary NTP Server
While the device is synchronized by the secondary NTP server, it continues to cyclically poll the primary NTP
server. The device will only switch back to the primary NTP server if it receives correct time information and if
none of the criteria for Redundant NTP Servers are fulfilled anymore.
External Time Synchronization via Fieldbus
The external time synchronization via fieldbus is used if the device is connected to the systems control via the
protocol Modbus RTU or IEC 60870-5-103 using the RS485 interface.
The time information can also be transmitted from the systems control via Modbus TCP or IEC 61850 using
Ethernet interfaces. When using the Ethernet connection, Siemens recommends to synchronize the device
from an NTP server.
When using the external time synchronization via fieldbus, the client should send a message containing the
time information to the device in 1-minute cycles.
The time synchronization error using the Modbus RTU protocol or IEC 60870-5-103 is ±20 ms maximum.
Basic Functions
2.4 Time Synchronization
42
SICAM, SICAM P850/P855 7KG85X, Manual
E50417-H1040-C482-A9, Edition 03.2022
Содержание SICAM 7KG85X
Страница 1: ...SICAM 7KG85X Power Monitoring Device SICAM P850 Power Quality Device SICAM P855 www siemens com SICAM ...
Страница 7: ...6 SICAM SICAM P850 P855 7KG85X Manual E50417 H1040 C482 A9 Edition 03 2022 ...
Страница 29: ...28 SICAM SICAM P850 P855 7KG85X Manual E50417 H1040 C482 A9 Edition 03 2022 ...
Страница 99: ...98 SICAM SICAM P850 P855 7KG85X Manual E50417 H1040 C482 A9 Edition 03 2022 ...
Страница 233: ...232 SICAM SICAM P850 P855 7KG85X Manual E50417 H1040 C482 A9 Edition 03 2022 ...
Страница 259: ...258 SICAM SICAM P850 P855 7KG85X Manual E50417 H1040 C482 A9 Edition 03 2022 ...
Страница 277: ...276 SICAM SICAM P850 P855 7KG85X Manual E50417 H1040 C482 A9 Edition 03 2022 ...
Страница 281: ...280 SICAM SICAM P850 P855 7KG85X Manual E50417 H1040 C482 A9 Edition 03 2022 ...