ABB TPU2000 Technical Manual page 40

TPU2000/2000R Modbus/Modbus Plus/ Modbus TCP/IP Automation Guide
IRIG B receivers/converters can format the IRIG B synchronization frames as a TTL-level pulse width,
Manchester Encoded or Modulated Carrier Frequency signal. TTL-level signals are pulse DC with a voltage
range of 0 to 5V. Modulated Carrier Frequency signals are pulse coded AM signals with modulation (tone bursts).
IRIG B is a general designation for time synchronization. There are many subsets to the IRIG B format. These
were developed to provide functionality primarily for military applications dealing with missile and spacecraft
tracking, telemetry systems, and data handling systems. IRIG B was embraced by the utility industry to answer a
need to provide a sequence of events capability between a group of substations. Care must be exercised to
match the device demodulating the signal from the satellite (downlink converter) with the IED's requiring specific
IRIG B code formats.
DPU/TPU/GPU products support Pulse Width Code (X= 0), whereas, REL 3XX products having an IRIG B Poni
Card support Pulse Width Code and Sine Wave Amplitude Modulated, and REL5XX products support Sine Wave
Amplitude Modulated IRIG. If the IRIG signal supplied to the device is one in which the attached device cannot
decode, the IED shall not synchronize with the signal and IED will not calculate time correctly.
The IRIG B time code has a one second time frame. Every frame contains 30 bits of Binary Coded Decimal time
information representing seconds, minutes, hours, days and a second 17 bit straight binary time-of-day.
frame has internal time markers, which insure time-stamping accuracy to the millisecond. An eight millisecond
frame reference marker appears during the first ten milliseconds of each frame. Another eight millisecond
position identifier appears during the ninetieth millisecond of each one hundred millisecond period mark. The 30
bit Binary Coded Decimal time data occurs in the first one hundred millisecond of each 1 second frame. Optional
control functions are sometimes encoded in the data stream. These functions control deletion commands and
allow different data groupings within the synchronization strings. Decoding an IRIG B pulse is quite a complex
undertaking. A typical 1 second time frame is illustrated in Figure 4-10. It is interesting to note that the year is not
included within the IRIG B frame. If the Control Function frame (CF) or Straight Binary Time of Day frame (SBT) is
not used, the bits defined within those fields are to be set as a string of zeroes and sent to the IED IRIG B
receiver.
A. Satellite Synch
Signal Received.
Figure 4-9. Typical IRIG B Architecture
B. Dish Sends received signal
to the downlink/receiver.
In the Substation
True Time
C. Demodulated signal transferred
to IEDs.
E C
E C
E C
The
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