The device wil interrogate both NTP servers cyclically every minute. It normally synchronizes itself on the first
parameterized, the primary NTP server. If the first NTP server doesn't respond to a query twice successively
within the 1 minute’s polling interval, the time synchronization switchovers to the secondary, second server.
Further switchover criteria are:
•
The server shows
alarm
on the response telegram (variable leap = 3)
•
The Stratum of the server is 0 (unknown) or greater than 3
•
The current time is indicated with 0 (if no reception, then Hopf)
•
The running time of the telegram in the net is greater than 5 ms
The switchover will be prevented if the second server does not deliver a considerably better time signal. For
example, if the server was last attainable for less than 10 minutes, if it announces
alarm
or its Stratum is 0 or
greater than 3, or if it indicates the current time with 0 , or the net running time of the telegram is greater
than 5 ms. In all of these cases the device is then no longer synchronized. It runs with the internal ms time
base and the last valid drift. After the parameterized time delay the device announces a time disturbance
signal.
While the module is synchronizing on the second server, it also interrogates the first server. The switch back to
the first server will only take place if it has performed at an acceptable quality for 10 minutes. The switch back
is delayed as long as all conditions are fulfilled.
At the startup of the module the first server will be interrogated then approximately 5 seconds later the
second server is interrogated as well. The time of the first server will also be taken if the Stratum is 0 or
greater than 3 or the second server offers a better Stratum.
The announcement of a time disturbance signal works purely from the view of the device. It will only be
announced if the device is no longer synchronized from the module.
For the redundant NTP client on the module this means that the announcement of the time disturbance signal
will not be issued during a successful switchover on the second server. If the time delay of the indication is
parameterized on the minimum value of 2 minutes in the device, which corresponds to a twice repeated
failure, then the behavior isn't determined and the indication could possibly appear. So for a defined behavior
the time delay for the time disturbance indication has to be parameterized up to at least 3 minutes. The time
delay for the time disturbance indication is not available as a parameter on the module and therefore can
neither be tested nor be used for an adapted switchover time (the above mentioned 10 min).
While switching back to the first NTP server no time disturbance indication will appear because the transition
takes place without loss of synchronization.
Some NTP servers are configurable to increase the Stratum from 1 to e.g. 6, if the satellite reception is faulty.
If the module detects that the Stratum value is 4 or higher, the flag
ClockNotSynchronized
is set immedi-
ately in all reports to be sent to the IEC client.
Setting the Time Zone
The Ethernet interface uses the UTC time format and a parameter for configuring the applicable rules for the
local time. Offset and daylight saving time are provided in Reydisp Manager.
Basic Structure of the Device Functionality
2.5 Real Time Clock
Reyrolle 7SR5, Transformer Protection Device, Device Manual
37
C53000-G7040-C015-1, Edition 11.2019
