2021-03-11

## What is line current distortion?

Line current distortion is quantified by various parameters including total harmonic distortion (THD), distortion factor (DF), and total demand distortion (TDD) while the DC voltage ripple is quantified by parameters such as ripple frequency, ripple factor, etc.

## What causes current distortion?

Most current distortion is generated by electronic loads, also called non-linear loads. These non-linear loads might be single phase loads such as point-of-sale terminals, or three-phase as in variable speed drives.

What is acceptable total harmonic distortion current?

While there is no firm limit in the US, IEEE 519 recommends that general systems like computers and related equipment have no more than 5% total harmonic voltage distortion with the largest single harmonic being no more than 3% of the fundamental voltage.

### What is 2nd harmonic distortion?

Second order harmonic distortion is the amount of 2nd order harmonic content present in the output signal with respect to the fundamental frequency.

### What are the types of waveform distortion?

There are five main types of waveform distortions: DC offset, harmonics, interharmonics, notching and noise. DC offsets are instances where direct current (DC) overlaps an alternating current (AC) distribution system. This overlapping of two different types of current can cause overheating in the equipment.

What is the difference between harmonics and transient?

Transient waveforms exhibit high frequencies that are produced at the period of switching process. Harmonics arise in steady state or for several seconds and are not related to the switching operation. They are the natural frequency of the system and are not related to the fundamental frequency.

#### What is VTHD and ITHD?

A simple single parameter to measure the overall effect of harmonics is the Total Harmonic Distortion, THD. This is the ratio (in %) between the r.m.s. value of all the harmonics together, and the fundamental. For voltage and current it may be referred to as VTHD and ITHD respectively.

#### What causes high Total Harmonic Distortion?

Harmonic distortions are usually caused by the use of nonlinear loads by the end users of electricity. Nonlinear loads, a vast majority of which are loads with power electronic devices, draw current in a nonsinusoidal manner.

What is DPF power factor?

Displacement Power Factor (DPF) is the phase angle between the fundamental voltage and current. Inductive loads cause current to lag behind voltage, while capacitive loads cause current to lead voltage.