Detect and eliminate harmonics: why?

Harmonic disturbances

Harmonics flowing in distribution networks represent disturbances in the flow of electricity. The quality of electrical power is deteriorated, and the efficiency of the system is decreased.

Here are the main risks linked to harmonics:

• Overload of distribution networks due to the increase of r.m.s. currents,
• Overload of neutral conductors, which current can exceed the phase currents,
• Overload, vibration and premature ageing of generators, transformers and motors as well as increased transformer hum,
• Overload and premature ageing of Power Factor Correction capacitors,
• Distortion of the supply voltage that can disturb sensitive loads,
• Disturbance in communication networks and telephone lines.

Economic impact of disturbances

All these disturbances have an economic impact:

• Premature ageing of equipment means it must be replaced sooner, unless oversized right from the start,
• Overload on the distribution network means higher equipment rating, increased subscribed power level for the industrial customer, and increased power losses,
• Unexpected current distortion can lead to nuisance tripping and production halt.

A necessary concern for the design and management of electrical installations

Harmonics are the result of the always expanding number of power electronic devices. They have become abundant today because of their capabilities for precise process control and energy saving benefits. Typical examples are Variable Speed Drives in the Industry, and Compact Fluorescent Lamps in commercial and residential areas.

International standards have been published in order to help the designers of equipment and installations. Harmonic emission limits have been set, so that no unexpected and negative impact of harmonics should be encountered. In parallel to a better understanding of effects, solutions have been developed by the Industry.

Harmonic consideration is now a full part of the design of electrical installations.