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Spurious triggers of transient module on ION 7550/7650 and ION8800

Issue
ION 7650/7550 and ION 8800 series devices can cause spurious triggering of the transient module when transients do not exist. This issue exists in firmware up to and including V354 for the ION 7650 and V334 for the ION 8800.

Symptoms
ION meters displaying this issue will find the transient module on ION 7650 and ION 8800 devices will trigger intermittently or with a fairly regular pattern (i.e. about every 15 minutes) while no corresponding real observable transient event actually occur in the monitored electrical system. The following observations may be describing this issue:

  1. Too many transients events being triggered. Unduly frequent transient events being recorded with associated waveform captures.
  2. Inspection of the waveform captures from transient events show no changes of the waveform.
  3. Transient module triggering regularly with no real corresponding power quality events in the actual physical electrical system being monitored.
  4. Adjustment of the transient module's threshold value doesn't seem to make much difference to the rate of transient triggers.
  5. Re-programming of the meter framework (by pasting the framework from a healthy meter, for example) does not fix the problem.
  6. Newer meters such as the ION 7650 and ION8800 show this problem while older ION meters (ION7600 and ION 8500) with the same or similar framework seem to be immune.​
Product Lines
ION7650
ION8800

Environment
Transient Module

Cause
The issue is observed when a large nominal voltage (approximately 131,000) is linked to the transient module. The nominal voltage is multiplied internally by the maximum A/D count value, and with the large nominal voltage this calculation overflows a 32-bit integer. The problem will be most noticeable when the nominal voltage is slightly larger than the roll -over value - in this case, the roll-over will result in a very small transient threshold value, and therefore a large number of transients detected. E.g. nominal voltages of 131,000 or 262,000 will be most noticeable, while a nominal voltage of 250,000 would not be as noticeable."

 

Resolution
Update the firmware to V355 or newer for the ION 7650 and V340 or newer for the ION 8800.

If a firmware upgrade is not possible or spurious triggers still persist, scale down the nominal voltage input to the transient module, and increase the threshold setting by a proportionate amount.
E.g. If the nominal voltage was 140,000, and the threshold was 25%, make the nominal voltage 70,000 and the threshold 50%. This would detect transients with the same sensitivity as the original settings, but the reported values would be different (i.e. the reported magnitude would be twice as large, and the reported nominal would be half of what it should be). The framework would also have to be modified so that a custom value was linked into the transient nominal - otherwise changing this setting would affect other operations on the meter such as sag/swell detection.

*This issues only affects PRODUCTS with transient capability. This issue affects other product lines with transient capabilities (ie. ION 8500, ION 7600) although only for voltages above 1MV so in practicality it should not appear.

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