Hi,

I am working on tracing current unbalance in HV systems. All papers study unbalance based on simulations which may fail in practical conditions. I'd like to know whether there is any standard for CT/CVT accuracy class used for current/voltage unbalance measurement or not. I have read IEC60044-1 and IEC60044-5 for CT/CVT standards. There is also IEC 61000-4-30 which defines unbalance measurement classes and it is indicated that CT/CVT accuracy may affect measured current/voltage unbalance ratio in practice (which is obviously correct), but no numerical analysis is provided and here my problem arises. Let's say maximum accepted voltage unbalance in HV systems is 1%. A low-accuracy CVT (say 3% class) may cause a voltage unbalance of 1%. In other words a BALANCE system look UNBALANCE or vice versa. Is there any standard that provide unbalance limit + measurement instrument's accuracy class?

Something like:

If you are using a CVT of 3% accuracy class, maximum acceptable voltage unbalance is 2%.

If you are using a CVT of 1% accuracy class, maximum acceptable voltage unbalance is 1%.

(I know IEC61000-3-13 is another standard related to unbalance, but unfortunately I don't have access to it)

Regards