GE 750, Инструкция по эксплуатации

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GE Power Management 750/760 Feeder Management Relay 16-
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16 COMMUNICATIONS 16.3 MODBUS PROTOCOL
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The samples are stored in a circular buffer; the figure below shows how a waveform might be stored for one
channel. The ‘Trace Memory Start Index’ determines where the waveform begins in the buffer. Likewise, the
‘Trace memory Trigger Index’ determines where the trigger point is. In this example the Start Index is 96 and
the Trigger Index is 224; note that the indices are always a multiple of sixteen.
Figure 16–1: TRACE MEMORY CIRCULAR BUFFER
The following example illustrates how information can be retrieved from Trace Memory:
1. A SCADA system polls the Number of Trace Memory Triggers register once every minute. It now reads a
value of 4 from the register where previously the value was 3 which means that a new data has been cap-
tured. The SCADA system proceeds with the following steps to read all the waveform data. After these
steps it resumes polling the Number of Trace Memory Triggers register.
2. Read Trace Memory Buffer Organization setpoint
3. Write a value of 4 to the Trace Memory Number Selector
4. Read all the Trace Memory Information registers and store to SCADA memory
5. Set variables TMCS and TMSS to 0
6. Write TMCS to Trace Memory Channel Selector
7. Write TMSS to Trace Memory Sample Selector
8. Read 64 samples from Trace Memory Samples and store to SCADA memory
9. Increment TMSS by 64
10. If TMSS < Total Number of Samples then goto 5
11. Increment CS by 1
12. If TMCS < total number of channels available then goto 4
13. Done
All the Trace Memory data for the most recent trigger is now stored to SCADA memory. The SCADA software
could now ‘unravel’ the circular buffers using the Start Index and Trigger Index registers that were read in step
3 and store them permanently to file or perhaps generate a graphical picture.
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0 16 32 48 64 80 96 112 128 144 160 176 192 208 224 240 256
Phase A Current