ABB Relion 650 Series Technical Manual page 555

1MRK 506 326-UUS B
synchronization, that is, for adjusting the internal clock to obtain zero offset at the next
coming time message.
• If the synchronization message has an offset that is large compared to the other messages, a
spike-filter in the IED removes this time-message.
• If the synchronization message has an offset that is large, and the following message also has
a large offset, the spike filter does not act and the offset in the synchronization message is
compared to a threshold that defaults to 500 milliseconds. If the offset is more than the
threshold, the IED is brought into a safe state and the clock is set to the correct time. If the
offset is lower than the threshold, the clock is adjusted with 10 000 ppm until the offset is
removed. With an adjustment of 10 000 ppm, it takes 50 seconds to remove an offset of 500
milliseconds.
Synchronization messages configured as coarse are only used for initial setting of the time. After
this has been done, the messages are checked against the internal time and only an offset of more
than 10 seconds resets the time.
Rate accuracy
In the IED, the rate accuracy at cold start is 100 ppm but if the IED is synchronized for a while, the
rate accuracy is approximately 1 ppm if the surrounding temperature is constant. Normally, it
takes 20 minutes to reach full accuracy.
Time-out on synchronization sources
All synchronization interfaces has a time-out and a configured interface must receive time-
messages regularly in order not to give an error signal (TSYNCERR). Normally, the time-out is set
so that one message can be lost without getting a TSYNCERR, but if more than one message is
lost, a TSYNCERR is given.
16.3.8.3 Synchronization alternatives
Two main alternatives of external time synchronization are available. The synchronization
message is applied either via any of the communication ports of the IED as a telegram message
including date and time or via IRIG-B.
Synchronization via SNTP
SNTP provides a ping-pong method of synchronization. A message is sent from an IED to an SNTP
server, and the SNTP server returns the message after filling in a reception time and a
transmission time. SNTP operates via the normal Ethernet network that connects IEDs together in
an IEC 61850 network. For SNTP to operate properly, there must be an SNTP-server present,
preferably in the same station. The SNTP synchronization provides an accuracy that gives 1 ms
accuracy for binary inputs. The IED itself can be set as an SNTP-time server.
SNTP server requirements
The SNTP server to be used is connected to the local network, that is not more than 4-5 switches
or routers away from the IED. The SNTP server is dedicated for its task, or at least equipped with a
real-time operating system, that is not a PC with SNTP server software. The SNTP server should be
stable, that is, either synchronized from a stable source like GPS, or local without synchronization.
Using a local SNTP server without synchronization as primary or secondary server in a redundant
configuration is not recommended.
Synchronization via IRIG-B
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 numbers stating if and how the signal is modulated and the
information transmitted.
Line distance protection REL650
Technical manual
© Copyright 2011 ABB Power Grids. All rights reserved
Section 16
Basic IED functions
M11346-93 v2
M11346-96 v2
M11346-3 v3
M11346-33 v2
GUID-588FCD12-C494-445E-8488-8287B34EFD9A v3
M11346-146 v5
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