ABOUT HARMONICS

Global Experience, Local Application

Wömner Academy
We follow developments and solutions in the field of Power Quality all over the world and share them with you in our trainings. Maintenance and repair trainings for factories, compensation design and calculation trainings for panel manufacturers or project companies can be provided on request. We also offer trainings to evaluate harmonics, resonance, power quality measurements upon special requests.

Harmonics About
In Turkey, Dunay basically a large part of the mains frequency 50Hz, US, Canada and 60 Hz is used in some countries such as Mexico. Harmonics are "multiple coefficients of your fundamental frequency".
Let's say "x" for our basic grid frequency 50Hz.

Second Order Harmonic (2 * x) = 100 Hz
Third Order Harmonic (3 * x) = 150 Hz
Fifth Order Harmonic (5 * x) = 250 Hz
Seventh Order Harmonic (7 * x) = 350 Hz

In the 3-phase alternating current system, our power comes from RST or ABC or L1-L2-L3 phases separated by 120 degrees from each other. (Shown as ABC in the table) It is very important that this phase sequence takes place as specified and it determines the direction of movement of the work we want to do. When phases A-B-C are connected in phase order, ie at 0-120-240 degree angles, the motor magnetic field occurs in the direction we want and the motor starts moving. This is the positive phase sequence.

Together, we will take a closer look at one of the consequences of harmonics being a source of trouble for many industrial or commercial businesses.



Harmonics like the 7th "rotating" in the same order as the fundamental frequency are called positive phase order. Harmonics such as 5 "rotating" in reverse order with respect to the fundamental frequency are called negative phase order. However, third harmonics that never "rotate" because they are in phase with each other are called zero phase order.

What happens in practice is that harmonics of 3 and 3 are mathematically summed up, while harmonics with positive and negative phase order help partially compensate for each other. Zero phase sequence harmonic currents only occur when phase-neutral is connected in a three-phase + neutral distribution system for non-linear loads. Positive and negative phase sequence harmonics are present in every 3-phase system without linear loads.

The presence of harmonics does not mean that factories or commercial enterprises cannot function properly. Like other power quality phenomena, it depends on the "characteristic" of the power distribution system and the tolerance level of the equipment. A facility with good tolerance can work properly even if it is a source of high harmonics. However, the harmonic component may affect the more sensitive neighboring facilities through the common electricity distribution system. At this point, it is recommended that businesses have network analysis done and examined in detail.

Faruk Başar
faruk.basar@womner.com