Evaluating Harmonics 1

[HYDL]

I've been monitoring Harmonics at a 911 call center. They have two 12.5 KVA, 1-phase UPS at 240 volt. The 208 volt system has a boost transformer for each for the 240 volt.

I've review the IEEE 519-1992 document. 3.5% is the highest THD that I've measure at the line side of the system. So, it appears that the system voltage harmonics are below the 5% standard called out in this document. However, it appears that the current harmonics measured might be outside outside the IEEE standard with THD varying between 8 and 22.

If the voltage harmonics are ok, are the current harmonics a concern?

 

[jghrist]

The current harmonic limits are to prevent your system from causing harmonic problems on the utility system. They are measured on the full service load. Higher levels for parts of your system are OK as long as they do not cause problems on your power system, which is unlikely with a 3.5% voltage THD.