Case Study: Preventing Damaging Harmonics Note: This Case Study can also be found in the sidebar of the Power Quality Application

When one of our customers was experiencing high neutral currents, BEST was called out to check and record temperatures on a 150kVA zig zag type transformer. A power quality analyzer was used to determine harmonic amplitudes and waveform distortions. The transformer temperature was 249.5F with a 3rd harmonic RMS 401.6 amps. and a 9th harmonic RMS 124.0 amps.

It was recommended that a 3rd harmonic filter/blocker be installed to reduce the RMS neutral current at the power source, thus reducing the entire systems harmonic load.

After the harmonic blocker was installed the transformer was retested 6 days later. Temperature were reduced by 15.0 degrees F, but most importantly the 3rd harmonic was reduced by 393.6 Amps RMS current to a total of 8 Amps RMS current. With the same loads we saw a reduction in the phase current by 7 to 12% with an increase in power factor and improved current waveform.

The installation will allow the customer to add additional loads without up sizing the electrical system and should see a return on investment in less than 24 months with an increase in transformer life.

Annual savings due to reduction of harmonic current losses:
$ 8,278

Annual savings due to reduce need for heat removal:
$ 2,030

Total Annual Savings:
$10,308