What is Harmonic? Why is it Important?

In electrical networks, the concept of harmonics is often mentioned together with reactive power and sometimes these two concepts can be confused with each other.

Although harmonic literally means ‘harmony’, in electrical engineering, it refers to unwanted frequency components that occur in the form of integer multiples of the fundamental network frequency.

These components combine with the fundamental frequency and distort the current-voltage wave structure. As a result, many negative effects such as heating in electrical devices, malfunction in switching equipment, communication problems occur.

If we consider the graph in the picture, the black component shows the mains voltage with 50 Hz fundamental component, the component with 3 times the full wavelength expressed in blue shows the 3rd harmonic with a frequency of 150 Hz, the component with 5 times the full wavelength expressed in green shows the 5th harmonic expressing 250 Hz. As a result of these three frequency components, the wave structure is distorted and the composition structure expressed in red is seen.

What are the Types of Harmonics?
Harmonics are usually generated by some devices located at consumption points. Harmonics are classified under three main headings:

1. Single Storey Harmonics

Odd multiples of the fundamental frequency (e.g. 3rd, 5th, 7th harmonics).

2. Double Harmonics

Double multiples of the fundamental frequency (e.g. 2nd, 4th, 6th harmonics).

3. Inter-harmonics

Intermediate frequencies that are not an exact multiple of the fundamental frequency.

Note: The harmonics that are usually tried to be eliminated are single-layer harmonics.

How are Harmonics Measured?
Harmonics are measured by energy analysers in the network and shown in percentages. Three different percentage representations are available;

· Total Voltage Harmonic Distortion Rate (THDv)

· Total Current Harmonic Distortion Rate (THDi)

· Total Demand Current (maximum drawn current) Harmonic Distortion Rate

When calculating the solution against harmonics, the distortion in the total demand current is considered. Measurements must be a minimum of one week.

What are the harms of harmonic distortion?
Harmonics are not only a quality problem, but also carry economic and technical risks:

Loss of productivity
Increase in operating costs
Intermittent power cuts
Sensitive device malfunctions
Overheating in motors and transformers
Operating time losses

One of the most common sources of harmonics is motor drives. The semiconductors used in these drives send harmonic currents into the grid during tripping.

The result

Harmonics is a critical issue in terms of energy quality. It is possible to minimise this problem with the right analysis and the right solutions.

As Aha Technology, we guarantee energy quality in your business with the solutions we offer.