Which one is more accurate ? single phase impedance or 3 phase impedance measurement ?

[coolme]

Hi guys,

Can we say that single phase measurement of impedance is more accurate than 3 phase measurement ? OK, they are different from each other, but does that mean one of them is more trustable ?

 

[electricpete]

I'd imagine that it will depend on depend what type of device you are measuring and what type of impedance you are trying to estimate. I would imagine to estimate the positive sequence impedance of a transformer you'd want to have balanced three phase conditions to the extent possible (to avoid negative and potentially zero sequence components).

If you clarify the equipment and purpose I'll bet you get a lot more response. (I'm sure others like prc can tell all about measuring transformer impedance much better than me)
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(2B)+(2B)' ?

 

[marks1080]

If you're actually measuring the impedance than they are both equally accurate. You need to understand what you're actually measuring first before you use the data though.

If you're estimating, or modelling, impedance than you're probably assuming a balanced system. So if the estimate doesn't really match up with the actual measured values, it may be because your assumptions are off. Keep in mind the measured values will include positive, negative and zero sequence quantities.