Snap shot measurements of Harmonics?

[vaaoc1425]

I like to know whether a “snap shot measurements [Instantaneous] measurements are acceptable for Harmonics analysis of an existing electrical system? Is there an IEEE standard specifies how it should be measured. I have an electrical consultant basing his UPS design on an existing electrical system on his snap shot Harmonics measurements.
According to his analysis, things are good to go! I do not feel too comfortable about his approach!

 

[ozmosis]

IEEE519.2 is the standard to look at.
Here in the UK we have G5/4 and is similar to IEEE519.2 in a number of areas.
The assessment part of ER G5/4 is undertaken using averaged measurements over a minimum ten-minute period. Further these results are subject to a 95% statistic rule which ‘smoothes’ out peak values and readings that are not part of the norm.
The measurement process is concerned with capturing the normal operating of a process or site. Abnormal loading or operating of loads during testing of a process need not be considered. Where the loads are not ‘normal’ the results can be extrapolated to ensure the measurements are representative.
If your site operates 24/7, then a more detailed assessment may be required. A 7 day measurement ensures that all Distortion Levels are assessed, and in particular the areas of maximum distortion such as evenings and weekends. It is at these points when other users and in particular domestic consumers can be affected.

 

[vaaoc1425]

Thank you very much.
That answers my concerns.