Determination of harmonics during design process 2

[Colinjohnson]

Gentlemen (and ladies),

Is there a rule of thumb for approximating the triplen harmonics which are produced by IT and other equipment which would assist in calculating transformer size during the design process ?

In the UK the normal power system within a commercial building will comprise a three phase star connected system split down into 3 single phase services.

Too often it emerges that the transformer is underratted or the neutral conductor is overheating due to triplen harmonics from light fittings, computers, servers, UPS etc.

Is there any guidance for the designer published to allow him to make the necessary allowances ?

 

[RonShap]

Many manufacturers of k factor rated transformers suggest various k factor ratings dependent on the percentage of connected non-linear load as compared to full load. For example, the following is from the Ge industrial website
"For commercial applications with significance nonlinear electronic loading, use K=4 for systems with 50% connected nonlinear electronic loads; K=13 for systems with 100% connected nonlinear electronic loads."

 

[RalphChristie]

Colinjohnson

Maybe not really related to your question, but check also the guide to the application of Engineering Recommendation G5/4 - In the assessment of harmonic voltage distortion and connection of non-linear equipment to the electricity supply system in the UK.

http://194.130.244.127/EnergyCentre/downloads/G5_4 Installation Guidelines (EA).pdf

and also

http://www.lenze.co.uk/multimedia/HARM2002.pdf

for additional info

Regards
Ralph