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Transformer correction of Power factor according to ASME PTC 22

Transformer correction of Power factor according to ASME PTC 22

Transformer correction of Power factor according to ASME PTC 22

(OP)
Could you please help me understand how the code gets the 'total secondary side phase shift'?

E.g how do I get 3.3 from 20.3; 2 and -1? See attached file.

RE: Transformer correction of Power factor according to ASME PTC 22

I believe this is referring to the phase angle error of the current transformers used for metering.  This data comes from the CT test data.  If the metering accuracy class is known, a worst-case phase angle error could be determined.  I assume total secondary side phase shift would also include the current phase shift that occurs due to the inductance of the secondary wiring and meter burden.

As you probably know, this correction factor will be in very small fractions of 1%.  

If you can explain what you are trying to determine, you may get better answers.

 

David Castor
www.cvoes.com

RE: Transformer correction of Power factor according to ASME PTC 22

Dave- you have it correct.

PTC 22 is used to verify performance test results for efficiency (heat rate) and  power output of power generation facilites.  The procedure tries to account for all errors in readings and adjusts data for known errors such as CT and VT ratio and phase shift.   If the error is unknown, the standard applies statistical analysis to calculate an overall confidence level for the result.

Thetest  results are usually worth many $1,000 per kw so there is a lot of interest in making them very accurate.

The total secondary side phase shift is the sum of the CT and VT phase shift errors and the meter phase shift errors.  The errors have to be determined by lab tests because they are so small it is difficult to accurately perform a filed measurement.

RE: Transformer correction of Power factor according to ASME PTC 22

(OP)
Hi,

Thanks for your replies!

That is correct as you wrote and I can calculate the CT and VT phase angle errors from their ceritficates as well as the power meter's errors (i.e. alpha, beta and gamma). At this point the only question is how I add them.

I think I also managed to calculate the ratio correction factors according to ASME.  

RE: Transformer correction of Power factor according to ASME PTC 22

hnagy,

The only way that I can think on how to arrive at the total secondary side phase shift values indicated in the code is by tweaking the given formula.

Use -(alpha-20) + beta - gamma.

However, I don't know if this would be acceptable, but it works...

http://www.powerqualityworld.com

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