a
b
c
en05000251.vsd
IEC05000251 V1 EN
Figure 504:
Binary minute pulses
The default time-out-time for a minute pulse is two minutes, and if no valid minute
pulse is received within two minutes a SYNCERR will be given.
If contact bounce occurs, only the first pulse will be detected as a minute pulse. The
next minute pulse will be registered first 60 s - 50 ms after the last contact bounce.
If the minute pulses are perfect, for example, it is exactly 60 seconds between the
pulses, contact bounces might occur 49 ms after the actual minute pulse without
effecting the system. If contact bounce occurs more than 50 ms, for example, it is less
than 59950 ms between the two most adjacent positive (or negative) flanks, the minute
pulse will not be accepted.
Binary synchronization example
An IED is configured to use only binary input for time synchronization, and a valid
binary input is applied to a binary input card. The HMI is used to tell the IED the
approximate time, and the minute pulse is then used to synchronize the IED. Minute
pulse means that each pulse occurs one minute after the previous pulse, so the first
pulse is not used at all. The second pulse will probably be rejected due to the spike
filter. The third pulse will give the IED a good time, and will reset the time so that the
fourth pulse will occur on a minute border. After the first three minutes, the time in the
IED will be good if the coarse time is set properly via the HMI or if the RTC backup
still keeps the time since last up-time. If the minute pulse is removed, for example, for
an hour, the internal time will drift by maximum the error rate in the internal clock. If
the minute pulse is returned, the first pulse is automatically rejected. The second pulse
will possibly be rejected due to the spike filter. The third pulse will set the time if the
time offset is more than 500 ms or adjust the time if the time offset is small enough.
If the time is set, the application will be brought to a safe state before the time is set.
If the time is adjusted, the time will reach its destination within one minute.
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.
Section 20
1MRK502052-UEN B
Basic IED functions
1114
Technical manual
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