Electrical power system harmonic problems are mainly due to the substantial increase of non-linear loads due to the technological advances, such as the use of power electronic circuits and devices, in ac/dc transmission links or loads in the control of power systems using power electronics or microprocessor controllers. Such equipments create load-generated harmonics throughout the system.Prior to the appearance of power semiconductors, the main sources of waveform distortion were electric arc furnaces, the accumulated effect of fluorescent lamps and to a lesser extent electrical machines and transformers.
In general, harmonic sources are given below
- Converters,
- Devices which includes semi-conductor elements,
- Generators,
- Motors,
- Transformers,
- Lightening equipment working by gas discharge principle,
- Photovoltaic systems,
- Computers,
- Electronic ballasts,
- Uninterruptable power supplies,
- Switching power supplies,
- Welding machines,
- Control circuits,
- Frequency converters,
- Static VAR compensators,
- Arc furnaces,
- HVDC transmission systems,
- Electrical Communication systems.