PTs suitable for harmonics measurements

[Morteza2]

Hi all,

Does anyone know what kind of PTs would be suitable to use for harmonics measurements?

Note that in our application we need to do harmonic measurements at a high voltage bus, and since our measurement device can only go up to 1000v, we need to use a PT to step down the voltage to feed into our measurement device. But I am concerned about the type of PT to be used, so that it doesn't distort harmonics and affect the accuracy of the readings.

Thanks!

 

[JG2828]

I don't know anything on the subject but you may want to take a look at the following papers I found with google.

You may get a better response if you let people know the voltage level and the frequency response range you are looking for.

http://www.google.com/url?sa=t&rct=...EPEX6WueUoQPxo2ZQ&sig2=EpA1iPD7F1HdISzY3SNfag

http://ieeexplore.ieee.org/xpl/logi...ore.ieee.org/xpls/abs_all.jsp?arnumber=760148

http://ieeexplore.ieee.org/xpl/logi...lore.ieee.org/xpls/abs_all.jsp?arnumber=85836

 

[RRaghunath]

I understand Capacitive Voltage Transformers (CVTs) with PQ sensors provide the best response when the power system harmonics are to be reflected.
Electromagnetic VTs are not good enough for the purpose due to increased errors at higher frequencies.

 

[dpc]

Electromagnetic VTs are not good enough for the purpose due to increased errors at higher frequencies.

I think this is overstating the situation. I looked into this about 10 years ago and found some IEEE papers where testing was done to determine the frequency response of typical metering voltage transformers. I recall that normal transformers had reasonably good fidelity up through the 30th harmonic or so. These tests were done on 15 kV transformers.

The answer will depend somewhat on what frequencies you are interested in and the voltage level, but for normal power system harmonic measurements, normal voltage transformers work pretty well. In reality, there are usually not any other practical options in most situation.