Synchronization Alternatives - ABB RES670 Technical Manual

Section 22
Basic IED functions
22.1.3.3
770

Synchronization alternatives

Three main alternatives of external synchronization sources are available. The IED also
supports redundant time synchronization via both GPS and IRIG-B. The
synchronization message is applied:
• via GPS
• via IRIG-B
• via GPS + IRIG-B
Synchronization via Built-in-GPS
The built-in GPS clock modules receive and decode time information from the global
positioning system. The modules are located on the GPS time synchronization Module
(GTM). When leap seconds are applied to Coordinated Universal Time (UTC), both
GTM and IRIG-B modules add/remove the leap seconds at the proper time. However,
GTM does not provide the bits for indicating leap second status (Bit 4: Leap Second
Pending, Bit 5: Leap Second Occurred, Bit 6: Leap Second Direction) as defined in the
Message Time Quality Flag bits according to the IEEE C37.118.2-2011 standard.
Synchronization via IRIG-B module
IRIG-B is a protocol used only for time synchronization. A clock can provide local
time of the year in this format. The "B" in IRIG-B states that 100 bits per second are
transmitted and the message is sent every second. After IRIG-B there are numbers
stating if and how the signal is modulated and the information transmitted.
To receive IRIG-B there are two connectors in the IRIG-B module, one galvanic BNC
connector and one optical ST connector. IRIG-B 12x messages can be supplied via the
galvanic interface, and IRIG-B 00x messages can be supplied via either the galvanic
interface or the optical interface, where x (in 00x or 12x) means a number in the range
of 0-7.
"00" means that a base band is used, and the information can be fed into the IRIG-B
module via the BNC contact or an optical fiber. "12" means that a 1 kHz modulation is
used. In this case the information must go into the module via the BNC connector.
If the x in 00x or 12x is 4, 5, 6 or 7, the time message from IRIG-B contains
information of the year. If the x is 0, 1, 2 or 3, the information contains only the time
within the year, and year information has to be set via PCM600 or local HMI.
The IRIG-B module also takes care of IEEE1344 messages that are sent by IRIG-B
clocks, as IRIG-B previously did not have any year information. IEEE1344 is
compatible with IRIG-B and contains year information and information of the time-
zone.
It is recommended to use IEEE 1344 for supplying time information to the IRIG-B
module. In this case, send also the local time in the messages, as this local time plus
1MRK 511 408-UUS A
Phasor measurement unit RES670 2.2 ANSI
Technical manual
M11346-3 v7
M11346-39 v5
M11346-146 v8