Harmonics refer to the voltages or currents that operate at a frequency that is an integer multiple of the fundamental frequency. For instance, if the fundamental frequency (often referred to as the first harmonic) is 60Hz, the second harmonic is 120Hz, the third harmonic is 180Hz, and so on.

Causes of Harmonics:

Harmonics in power systems are mainly produced by non-linear loads. Non-linear loads are those that do not have a linear (or directly proportional) relationship between voltage and current. Common sources include:

  1. Variable speed drives
  2. Fluorescent lighting
  3. Computer power supplies
  4. Welding machines
  5. Uninterrupted Power Supplies (UPS)

Effects of Harmonics:

  1. Overheating: Harmonic currents can cause additional heating in electrical equipment, reducing the life of transformers, motors, and other devices.
  2. Resonance: Harmonics can resonate with power factor correction capacitors, leading to high currents and potential failures.
  3. Distorted Voltage Waveform: This can reduce the efficiency of motors and other equipment.
  4. Interference: Harmonics can interfere with communication systems.
  5. Increased Energy Costs: The presence of harmonics can increase power consumption due to inefficiencies.
  6. Equipment Malfunction: Some sensitive equipment may malfunction or fail prematurely due to harmonics.

Mitigation of Harmonics:

  1. Passive Filters: These are series LC circuits tuned to a specific harmonic frequency. They present a low impedance path for the harmonic, diverting it away from the system.
  2. Active Filters: These monitor the harmonics in a system and inject counteracting currents to cancel them out.
  3. Isolation Transformers: These can help reduce the transmission of harmonics.
  4. Use of Non-linear Load Devices: These can be designed to produce less harmonics.
  5. Detuned Power Factor Correction Capacitors: These are designed not to resonate with the most common harmonic frequencies.

Regular monitoring and evaluation of power quality can help in identifying and managing harmonic issues. Using harmonic analysis tools, one can pinpoint sources of harmonics and implement appropriate mitigation strategies.