Time Synchronisation; Demodulated Irig-B; Demodulated Irig-B Implementation; Figure 193: Gps Satellite Timing Signal - GE MiCOM P40 Agile Technical Manual

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TIME SYNCHRONISATION

In modern protection schemes it is necessary to synchronise the IED's real time clock so that events from different
devices can be time stamped and placed in chronological order. This is achieved in various ways depending on the
chosen options and communication protocols.
Using the IRIG-B input (if fitted)
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● Using the SNTP time protocol (for Ethernet IEC 61850 versions + DNP3 OE)
By using the time synchronisation functionality inherent in the data protocols
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8.1

DEMODULATED IRIG-B

IRIG stands for Inter Range Instrumentation Group, which is a standards body responsible for standardising
different time code formats. There are several different formats starting with IRIG-A, followed by IRIG-B and so on.
The letter after the "IRIG" specifies the resolution of the time signal in pulses per second (PPS). IRIG-B, the one which
we use has a resolution of 100 PPS. IRIG-B is used when accurate time-stamping is required.
The following diagram shows a typical GPS time-synchronised substation application. The satellite RF signal is
picked up by a satellite dish and passed on to receiver. The receiver receives the signal and converts it into time
signal suitable for the substation network. IEDs in the substation use this signal to govern their internal clocks and
event recorders.
V01040

Figure 193: GPS Satellite timing signal

The IRIG-B time code signal is a sequence of one second time frames. Each frame is split up into ten 100 mS slots
as follows:
Time-slot 1: Seconds
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Time-slot 2: Minutes
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Time-slot 3: Hours
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Time-slot 4: Days
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● Time-slot 5 and 6: Control functions
Time-slots 7 to 10: Straight binary time of day
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The first four time-slots define the time in BCD (Binary Coded Decimal). Time-slots 5 and 6 are used for control
functions, which control deletion commands and allow different data groupings within the synchronisation strings.
Time-slots 7-10 define the time in SBS (Straight Binary Second of day).
8.1.1

DEMODULATED IRIG-B IMPLEMENTATION

All models have the option of accepting a demodulated IRIG-B input. This is a hardware option and it uses the
same terminals as the RP1 (or RP2 if applicable) inputs. You cannot have IRIG-B and a serial port in the same slot.
This means 20Te models cannot have both IRIG-B time synchronisation and serial communications capability. For
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GPS time signal
Satellite dish Receiver
GPS satellite
IRIG-B
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Chapter 17 - Communications
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