ABB Relion 670 series - Adding New Users to the IED

protection. The two clock systems are synchronized by a special clock
synchronization unit with two modes, fast and slow. A special feature, an automatic
fast clock time regulator is used. The automatic fast mode makes the
synchronization time as short as possible during start-up or at interruptions/
disturbances in the GPS timing. The fast and slow settings are also available on the
local HMI.
The hardware and software clocks are synchronized also if a GPS clock is used or
if PTP (IEEE 1588) is in on-mode.
SyncLostMode is not required to set as Block/BlockonLostUTC when differential
protection is based on ECHO mode.
Fast clock synchronization mode
At start-up and after interruptions in the GPS, PTP or IRIG B time signals, the
deviation between the external time system and the internal differential time system
can be substantial. A new start-up is also required, for example, after maintenance
of the auxiliary voltage system.
When the time difference is > 16 μs, the line differential protection function is
blocked and the time regulator for the hardware clock automatically uses a fast
mode to synchronize the clock systems. Time adjustment is made with an
exponential function, that is, with big time adjustment steps in the beginning, and
then smaller steps until a time deviation between the GPS time and the differential
time system of < 16 μs has been reached. The protection function is then enabled
and the synchronization remains in fast mode or switches to slow mode depending
on the setting.
Slow clock synchronization mode
During normal service, a setting with slow synchronization mode is used. This
prevents the hardware clock to make too big a time steps (> 16 µs) emanating from
the requirement of correct timing in the line differential protection function.
3.2 Time synchronization using a built-in GPS receiver
GUID-1E6A6837-17F8-437E-B1DD-4296DC859351 v1
Telecommunication networks with unspecified route switching require that the line
differential protection IED's built-in GPS receiver is used. This way the protection
function can operate correctly independent of asymmetric delays in communication
channels.
The maximum allowed time deviation in a telecommunication network is 40 ms
representing the sum of deviations in both directions. It is also possible to make an
asymmetric split, for example 10 ms in one direction and 30 ms in the other
direction, because the deviation can be accurately measured when GPS timing is
available. With longer deviations, the protection function gets blocked.
Section 3 1MRK 505 382-UEN B
Common time synchronization
22 Communication set-up 670/650 series 2.2
Application Guide