Real-Time Clock (Rtc) Operation - ABB Relion 650 Series Technical Manual

1MRK 511 424-UEN B
15.1.3.2
Bay control REC650 2.2 IEC
Technical manual
Synchronization from
a higher level
Optional synchronization of
modules at a lower level
IEC09000342 V1 EN-US
Figure 277: Synchronization principle
A function is said to be synchronized when it periodically receives synchronization
messages from a higher level. As the level decreases, the accuracy of the
synchronization decreases as well. A function can have several potential sources of
synchronization, with different maximum errors. This gives the function the
possibility to choose the source with the best quality, and to adjust its internal clock
based on this source. The maximum error of a clock can be defined as:
• The maximum error of the last used synchronization message
• The time since the last used synchronization message
• The rate accuracy of the internal clock in the function.

Real-time clock (RTC) operation

The IED has a built-in real-time clock (RTC) with a resolution of one millisecond.
The clock has a built-in calendar that handles leap years through 2100.
Real-time clock at power off
During power off, the system time in the IED is kept by a capacitor-backed real-
time clock that will provide 5 ppm accuracy for at least two days. This means that
if the power is off, the time in the IED may drift with maximum 0.5 second per day
for two days, and after this the time will be lost.
Real-time clock at startup
At IED startup, the internal time is free running. If the RTC is still alive since the
last up time, the time in the IED will be accurate (may drift 35 ppm), but if the
RTC power has been lost during power off (will happen after 5 days), the IED time
will start at 2003-01-01. For more information, please refer to section
synchronization startup procedure"
Basic IED functions
Function
IEC09000342-1-en.vsd
and "Binary synchronization
Section 15
M11346-57 v4
M11346-60 v3
M11346-63 v4
"Time
example".
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