When Modbus TCP or DNP3 over TCP/IP is used, SNTP or IRIG-B timesynchronization should be used for better synchronization accuracy.With the legacy protocols, the synchronization message must be receivedwithin four minutes from the previous synchronization. Otherwise badsynchronization status is raised for the protection relay. With SNTP, it isrequired that the SNTP server responds to a request within 12 ms,otherwise the response is considered invalid.The relay can use one of two SNTP servers, the primary or the secondary server. Theprimary server is mainly in use, whereas the secondary server is used if the primary servercannot be reached. While using the secondary SNTP server, the relay tries to switch backto the primary server on every third SNTP request attempt. If both the SNTP servers areoffline, event time stamps have the time invalid status. The time is requested from theSNTP server every 60 seconds. Supported SNTP versions are 3 and 4.IRIG-B time synchronization requires the IRIG-B format B004/B005 according to the200-04 IRIG-B standard. Older IRIG-B standards refer to these as B000/B001 withIEEE-1344 extensions. The synchronization time can be either UTC time or local time. Asno reboot is necessary, the time synchronization starts immediately after the IRIG-B syncsource is selected and the IRIG-B signal source is connected.IRIG-B time synchronization requires a COM card with an IRIG-B input.When using line differential communication between RED615 protection relays, the timesynchronization messages can be received from the other line end protection relay withinthe protection telegrams. The protection relay begins to synchronize its real-time clockwith the remote end protection relay's time if the Line differential time synchronizationsource is selected. This does not affect the protection synchronization used in the linedifferential protection or the selection of the remote end protection relay's timesynchronization method. [1]3.5.1.3 SignalsTable 28:GNRLLTMS output signalsName Type DescriptionALARM BOOLEAN Time synchronization alarmWARNING BOOLEAN Time synchronization warning[1] The line differential protection is available only in RED615.Section 3 1MAC059074-MB ABasic functions84 615 series ANSITechnical Manual
