Harmonics cause interruptions, interference and downtime
Harmonics pollute the electrical network and make equipment connected to it behave erratically.
Harmonics can cause damage to sensitive electronic equipment, interference in communication equipment, and false readings on measurement devices. Harmonics can trip circuit breakers, blow fuses and cause capacitor failures. The effects also include overheating of transformers, cables, motors, generators and capacitors. Equipment must be designed to tolerate harmonics in the network and oversizing leads to higher investment costs and underutilized capacity.
The problems caused by harmonics result in increased losses because more energy is wasted due to overheating, equipment has a shorter life time and is subject to unreliable operation. In the worst cases, harmonics cause unnecessary and unwanted process interruptions.
In an ideal case, the current in an electrical grid is a pure sine wave and does not contain harmonics. In reality the current deviates from this pure sine wave and contains harmonics.
A pure sinusoidal voltage and current does not contain any harmonics.
Voltage and current that deviate from the sine form contain harmonics.
The total amount of harmonics is expressed as a THD% value (= total harmonic distortion).
What causes harmonics?
Harmonics are introduced into the electrical network by non-linear loads, such as
- power supplies of PCs, PLCs, TVs etc.
- photocopiers, domestic appliances
- diode and thyristor bridges
- uninterruptible power supplies
- motor starters
- switched-mode power supplies
- variable speed drives
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