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Good Evening,
I'm writing in to report a pretty strange observation that one of our customers encountered when using the PM8000 and the on-board web server GUI to view the capture voltage and current waveform. To set the basis of discussion, I am in Singapore, our power grid is 400Vac (Line-Line), 230Vac (Line-Neutral), 50Hz and grounding system is TN-S. The meter I am using to replicate the error is connected single phase, and hence only adheres to 230Vac (Line-Neutral), 50Hz and grounding system is TN-S.
The ION Setup version used is,
This is not the latest version which is build 18019 as that build crashes upon attempting to retrieve waveform from the PM8000.
The steps to recreate the problem observed on site is as follows,
1) Firmware update the PM8000 to the latest 1.4.1 firmware and using the 8000_v1.4.0_FAC-PQ_1.4.0.0.0.dcf
2) Set the meter to the following using ION Setup
3) Set the power quality settings to capture 256 samples/cycle for 7 cycles
4) Do a manual waveform capture trigger
Viewing on ION Setup, the waveforms captured on the PM8000 V1 and I1 inputs are as follows,
Nothing out of the norm. The timescale per cycle is exactly 0.020s which is 20ms, corresponding to 50Hz
But now if you view the same waveform (remember, you have flashed the new firmware, everything is erased), this is what you see,
Almost immediately you will realize the time indicated at the lowest point on the first cycle is not as indicated by ION Setup 9:08:18.821 PM but rather 13:08:18:81234 (not quite sure how you get below 1ms accuracy when our timestamp is only accurate down to 1ms). I noted that the web GUI gave the timing in UTC, hence correcting for GMT offset of +8, that gave 9:08:18.81234 PM
To matters worse, looking at the lowest point on the next cycle (that gives 1 full cycle, lowest point to lowest point)
The time indicated on the occurrence is 13:08:18.81806 UTC (9:08:18.81806 PM) where it is indicated in ION Setup as 9:08:18.841 PM
Taking the difference between the 2 adjacent lowest points on the waveform obtained from the web GUI, the total time elapsed is (9:08:18.81806 - 9:08:18:81234) = 0.00572s = 5.72ms. Since when has the frequency changed from 50Hz to well over 170Hz?
I repeated steps (1) to (4) with the exception that I modified step (3) to capture 32 samples/cycle for 54 cycles,
The capture was indicated as started at 13:29:58.07553 and the end time is indicated as 13:29:58.11548, that gives 0.03995s = 39.95ms and 54 cycles elapsed? That gives over 1350Hz in the voltage waveform.
Credit for the above goes to Shanelle Chan who was corresponding with the customer and detected this error in the web GUI. Without her persistence, I doubt this error would have been surfaced. In summary, the errors found as below,
- Web GUI reports timing in UTC while the device is set to 12 hour clock
- Time reported by ION Setup difference significantly from that reported on the web GUI waveform viewer
- Waveform timescale on the web waveform viewer is not correct
- Timescale error changes from bad to worse when more cycles of waveform is captured
Appreciate the engineering / development teams look into this matter with urgency as it is impacting the credibility of our products.
Best Regards,
Tan Kuan Khoon
Senior Specialist, PAE
EcoBuilding
Schneider Electric Singapore
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