Harmonics are disturbances, these waveforms are voltage or current waveforms, periodic, sinusoidal and are integer multiples of the fundamental frequency (50 or 60 Hz). In today’s industrial power distribution systems, non-linear equipment accounts for an increasing proportion of the total load used. Any equipment that has non-linear voltage and current characteristics generates harmonics. The main sources of harmonics in industrial power systems are static power converters, rectifiers, uninterruptible power supplies (UPS), power chargers, power electronic switches, inverters, arc furnaces and magnetic saturators are also sources of harmonics.
In addition, most of the main load components of the power system are mainly inductive loads combined with capacitors (capacitive loads) used to compensate for reactive power or filter harmonics that can lead to series or parallel harmonic resonance that amplifies current and voltage. Harmonics cause many impacts and affect the performance and operation of the power system as well as equipment. Therefore, harmonic analysis becomes an important part of the design and operation of the entire power system to help system managers monitor the level of harmonics, select equipment and harmonic filtering solutions, and propose measures to overcome, improve and minimize harmonics at an acceptable level.
♦ The effects of harmonics in power systems are very common as they affect electrical equipment, electronic equipment, system operation and performance. The effects of harmonics are caused by both current harmonics and voltage harmonics. Current harmonics cause problems such as overheating, overloading, reverse voltage harmonics cause voltage abnormalities such as overvoltage, voltage disturbance, insulation degradation and thus reduce the life of the equipment. If harmonics are not controlled within acceptable limits, electrical equipment and even electronic equipment can be damaged leading to power supply interruptions. Some of the common effects of harmonics are as follows:
– Distortion of current and voltage waveforms
– Increased losses and damage to equipment
– Voltage fluctuations, system overvoltage
– Overload, overheating and explosion of equipment
– Reduced equipment performance
– Incorrect measurement or malfunction of measuring and protection equipment
– Electromagnetic interference to telecommunication electronic equipment
♦ Parameters and data information provided when performing harmonic analysis include:
– Individual voltage and current harmonic distortion
– Total voltage and current harmonic distortion (%THD)
– Total current harmonic distortion at maximum load current (%TDD).
– Harmonic filter capacity and location
– Reactive power capacity required to compensate for the system
♦ Applicable standards:
– IEEE 519: Harmonics in Power Systems
– IEEE 399: Standard for Analysis of Industrial and Commercial Power Systems.