Howtosignalprocessing
- How the Total Harmonic Distortion is calculated?
- Why do we calculate THD?
- What is the acceptable limit of THD?
How the Total Harmonic Distortion is calculated?
The total harmonic distortion (THD or THDi) is a measurement of the harmonic distortion present in a signal and is defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency.
Why do we calculate THD?
THD gives information about non‑linear behavior
As mentioned above, Total Harmonic Distortion is a useful technique to analyze any non‑linear behavior of a system. You can do this with a Fast Fourier Transform (FFT). The measured signal is transformed from the time domain (see Figure 1) into the frequency domain.
What is the acceptable limit of THD?
The limits on voltage harmonics are thus set at 5% for THD and 3% for any single harmonic. It is important to note that the suggestions and values given in this standard are purely voluntary. However, keeping low THD values on a system will further ensure proper operation of equipment and a longer equipment life span.
