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Power harmonics are generated by many non linear loads such as Variable Speed Drives, Welding Tools, Arc Furnaces and Power Capacitors etc. As a result, A.C. power received from utility gets distorted and such distorted power adversely affects operation of other electrical equipment in the plant and potentially can affect other customers on the same power source.

The harmonics affect many types of electrical equipment. However, they can be harmful especially to the computer and data communication equipment.

In water and wastewater plants the principal examples of non- linear loads are variable frequency drives. Variable frequency drives are increasingly used for pumping and as final control elements. The paper discusses how to estimate the harmonics and what can be done to contain or bypass them and render them harmless

Harmonics generated by variable speed drives are due to their inherent design. One cannot change the design to eliminate them. However, external means can be provided to filter out, reduce or bypass the harmonics so that the power distortion is kept within limits and effect on other users as well as other plant equipment is minimized. The paper sites a case study in which how potential problems due to harmonics were effectively addressed during design and construction, thereby, minimizing costs and downtime.

Harmonics can be reduced by commercially available harmonic filters, line reactors or by isolation transformers. It is essential that the one must estimate the level of harmonics generated by non linear load and effectively choose, size deploy these devices at appropriate locations in the overall power distribution scheme. The paper describes how the process of harmonic determination can be simplified by making some intelligent assumptions and by using the commercially available software from variable speed drive manufacturers and makers of harmonic filters.

Document Type: Research Article


Publication date: 2002-01-01

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  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

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