FRA (Frequency Response Analysys Equipment

[EddyPach]

Can somebody tell me where I can find info on a a good RFA equipment from a good make? When asking for that equipment, which should be the paramenters to watch out if the equipment will be purchased?
Thanks for the info.

 

[electricpete]

For transformers I believe Framatome makes FRA equipment. I don't have any info about what's good and bad.

 

[busbar]

Maybe this is what you're searching for:

http://www.doble.com/presshtm/m5100new.htm

 

[electricpete]

Looking at busbar's link reminds me that there are two basic types of frequency response tests.

One applies an impulse in the time domain, measures a time response, and computes the FFT which represents the frequency response.

The other (as introduced by the Doble article) applies a swept sinusoid input, and measures the magnitude and phase of the response for each frequency.

Theoretically results of both tests are the same. In the real world the time-domain method will never recreate the true frequency response since only an approximation of an impulse can be created, and high frequency signals are a little trickier to measure. I really don't know how any of that translates to ability to diagnose transformers.

 

[EddyPach]

That´s the site, BUsbar. Thank you too, Electricpete

 

[prc]

Normally in power trfs FRA is done by applying 1-250Khz lowvoltage1-10V to one phase and measuring impedance and neutral current of it while keeping earthed all other windings.Measurements are made inb the entire range of 1-250KHZ range.Also voltage transfer ratio is taken to other windings.These form the benchmarks and any movement in the windings cause a change in the benchmarks.
If you are looking for laboratory models ,HP and Solirtron are also marketing suitable models.