7.12
SEL-787 Relay Instruction Manual Date Code 20150130
Communications
Communications Protocols
Telnet Server
Use the Telnet session (TPORT default setting is port 23) to connect to the
relay to use the protocols, which are described in more detail below:
➤ SEL ASCII
➤ Compressed ASCII
➤ Fast Meter
➤ Fast Operate
Telnet is a terminal connection across a TCP/IP network that operates in a
manner very similar to a direct serial port connection to one of the relay ports.
As with FTP, Telnet is a part of TCP/IP. A free Telnet application is included
with most computer operating systems, or you can obtain low-cost or free
Telnet applications on the Internet.
Ping Server
Use a Ping client with the relay Ping server to verify that your network
configuration is correct. Ping is an application based on ICMP over an IP network. A
free Ping application is included with most computer operating systems.
IEC 61850
Use as many as six sessions of MMS over a TCP network to exchange data
with the relay. Use GOOSE to do real-time data exchange with as many as
16 incoming messages and 8 outgoing messages. For more details on the
IEC 61850 protocol, see Appendix F: IEC 61850 Communications.
Simple Network Time
Protocol (SNTP)
When Port 1 (Ethernet port) setting ESNTP is not OFF, the internal clock of
the relay conditionally synchronizes to the time of day served by a Network
Time Protocol (NTP) server. The relay uses a simplified version of NTP called
the Simple Network Time Protocol (SNTP). SNTP is not as accurate as
IRIG-B. The relay can use SNTP as a less accurate primary time source, or as
a backup to the higher accuracy IRIG-B time source.
SNTP as Primary or Backup Time Source
If an IRIG-B time source is connected and either Relay Word bit TSOK or
Relay Word bit IRIGOK asserts, then the relay synchronizes the internal
time-of-day clock to the incoming IRIB-G time code signal, even if SNTP is
configured in the relay and an NTP server is available. If the IRIG-B source is
disconnected (if both TSOK and IRIGOK deassert) then the relay
synchronizes the internal time-of-day clock to the NTP server, if available. In
this way, an NTP server acts either as the primary time source or as a backup
time source to the more accurate IRIG-B time source.
Creating an NTP Server
Three SEL application notes, available from the SEL website, describe how to
create an NTP server.
➤ AN2009-10: Using an SEL-2401, SEL-2404, or SEL-2407 to
Serve NTP Via the SEL-3530 RTAC
➤ AN2009-32: Using SEL Satellite-Synchronized Clocks With the
SEL-3332 or SEL-3351 to Output NTP
➤ Using an SEL-2401, SEL-2404, or SEL-2407 to Create a
Stratum 1 Linux NTP Server
NOTE: Use the QUIT command prior
to closing the Telnet-to-Host session
to set the relay to Access Level 0.
Otherwise the relay will remain at an
elevated access level until TIDLE
expires.
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