Metering and Monitoring systems

[Johan_2023]

Hi there,
I recently did a Schneider online course "Metering and monitoring systems for power reliability and availability".  In this course, some core features were mentioned for the meters, and I have a question about one of these features.

Power Meters (Incoming) : Individual Harmonics up to 511th 

Power Meters (Critical Loads) : Individual Harmonics up to 127th 

Power Meters (Feeder) : Individual Harmonics up to 31th 

I would like to know the technical reason for these 511, 127 and 31 th. Is there any technical reason why the incoming need to measure up to 511 th (and not up to 127 instead)? and same for Critical loads 127th and feeder 31?

What happens if the incoming can't detect up to 511?

My question is because when I specify these features in the EMS technical specification, normally the client ask me "Why 511th, why 127 and why 31". 

Why not only 127 for the incoming if after the 100th the effects are not considerable?

Thanks

[Charles_Murison]

Hello @Johan_2023 ,

The maximum harmonic for a meter to be able to detect is (n/2 -1) where n is the sample rate. So a meter with sample rate of 1024 samples per cycle can have a maximum of 511th harmonic. 

Regards,

Charles

[DanL · Accepted solution]

technically, meters will often have other limits besides just the Nyquist limitation for harmonic bandwidth.

https://en.wikipedia.org/wiki/Nyquist_frequency

For example if the device implements a low-pass filter (such as required by IEC 61000-4-30 Class A) then on some designs, although it may be mathematically capable of registering a result for the "255th harmonic" from a captured waveform, the reading may not be valid or useful (b/c the signal was attenuated below the noise floor)