21.1.3 Operation principle
IP12360-1 v4
21.1.3.1 General concepts
M11346-77 v1
Time definitions
M11346-80 v3
The error of a clock is the difference between the actual time of the clock, and the time the clock is
intended to have. Clock accuracy indicates the increase in error, that is, the time gained or lost by
the clock. A disciplined clock knows its own faults and tries to compensate for them.
Design of the time system (clock synchronization)
GUID-E2B9E81C-5733-4521-B27F-BF33E05CCFB0 v6
The time system is based on software and hardware clocks that run independently from each
other. See figure 629
SW-time
Time-
Regulator
(fast or slow)
Time tagging and general synchronisation
Time-
Regulator
(Setting,
see
technical
reference
manual)
Comm-
unication
Events
Synchronization for differential protection
(ECHO-mode or GPS)
Diff.-
comm-
unication
*IEC 61850-9-2
Connected when GPS-time is
used for differential protection
IEC08000287-2-en.vsd
External
Synchronization
sources
Trans-
ducers*
LON
SPA
GPS
SNTP
IRIG-B
PPS
Off
Min. pulse
DNP
GPS
IRIG-B
PPS
Off
Protection
and control
functions
A/D
converter
HW-time
IEC08000287 V2 EN-US
Figure 629: Design of the time system (clock synchronization)
All time tagging is performed by the software clock. When, for example, a status signal is changed
in the protection system of a function based on the free running hardware clock, the event is time
tagged by the software clock when it reaches the event recorder. The hardware clock can thus run
independently.
The echo mode of differential protection is based on the hardware clock. Thus, there is no need to
synchronize the hardware clock and the software clock.
1MRK 502 066-UUS B Section 21
Basic IED functions
1247
Technical manual
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