Measure Power Supply

[woody 782]

Hi, I'm trying to measure the power quality of our power systems. However i'm having problems trying measure the phase difference of the voltage and current supplies that is measured. How do i capture the phase difference between 2 signals ? Another question would be the example for measuring the harmonic distortion. In that example we use a generated signal, how do i get it to measure the signal that i want it to measure (i.e. voltage) through channels instead of generated ones. Any help would be appreciated.

[preston_johnson]

Good Morning Woody,

In measuring Phase there are a couple of approaches. 1) is to take the real FFT of both signals (V and I) and to compare the phase outputs of the fundamental frequency, say 60hz. 2) compare the signal peak locations in the time domain and calculate phase as you would manually on an o-scope.

I have found both methods to work. 1) is easier to implement, 2) executes faster but has a bit more code calculating phase differences from array indexes.

I have also used the harmonic distortion VIs and to produce power harmonics from voltage and current waveforms. I'd like to send you an example to review. Can I get your email address?

I am also interested in learning more about your power systems quality measurements. I am working with
Emergent IT's Master Monitor LabVIEW software for power quality applications. You can see this product description on the NI system integration page under system integration products. I could also send you a data sheet.

Please contact me to discuss these. See you at NI Week?

Sincerely,

Preston Johnson
Business Development Manager
National Instruments
512-683-5444
preston.johnson@ni.com