Harmonics are disturbances to the sinusoidal voltage waveform. They are multiples of the supply frequency, i.e. the fifth harmonic would be 250 Hz if the supply frequency is 50 Hz. These deviations from the pure sine function are caused by non-linear loads from electrical machinery and appliances ranging from flourescent lighting and battery chargers to pumps and variable speed drives. High levels of harmonics can create voltage distortions and power quality problems.

Simply put: Harmonics are unwanted frequency components and unbalance in terms of uneven power distribution between the phases in the electrical network.

Power quality problems caused by harmonics can have detrimental and often expensive effects on machinery and appliances. Electric motors can become overheated with a higher frequency of break downs and a shortened life span. Some common direct impacts of poor power quality in the shape of harmonics are:

• Reduced production speed
• Increased energy consumption
• Charges for reactive power consumption
• Equipment damage
• Premature equipment aging
• Data loss

Harmonic Distortion Standards

Harmonics caused by large machine parks can also effect the grid, which is the reason for an increase in regulations and standards required by municipals. Some examples are IEEE 519, G5/4, EN 61000, EN 50160, D-A-CH-CZ, among others. There are also standards specific to certain applications, such as DNV or ABS for offshore applications. Most often the standards require voltage harmonic distortion to be below 5-8%.