What is harmonics???

Harmonics are currents or voltages with frequencies that are integer multiples of the fundamental power frequency. If the fundamental power frequency is 50 Hz, then the 2nd harmonic is 100 Hz, the 3rd is 150 Hz, etc. Harmonic frequencies from the 3rd to the 25th are the most common range of frequencies measured in electrical distribution systems.

Sources of harmonics
Harmonics are distorted normal electrical current waveform, generally transmitted by nonlinear loads. Single-phase non-linear loads are prevalent in modern office buildings, while three-phase, non-linear loads are widespread in factories and industrial plants.
Nonlinear loads  
  SMPS (Switch-mode power Supplies)
  Variable speed motors and drives
  Personal computers
  Fax machines
  Battery chargers and UPS
  Fluorescent lights ETC…
An effective strategy for harmonic mitigation is to isolate the harmonic currents near the loads themselves through passive filters, phase shifting and zero sequence filtering. By reducing the current harmonics, the voltage distortion, neutral-ground voltage and overheating that these harmonic currents produce will be dramatically reduced.
By drawing current in a non-sinusoidal manner, harmonic currents are circulated through the electrical distribution system which results in
Effects of harmonics  
  Neutral current
  Over heating of neutrals, transformers and other electrical distribution equipments
  Excessive voltage distortion and neutral- ground voltage
  Ground currents
  Higher energy lose
  Insulation damage
  Capacitor failures
  Pulsating torque’s in rotating machinery
  Interference with communication
  Control and signal circuits
  Mal operation of equipments
  Increased operating temperature on equipment
  Reduced capacitor life
  Blown fuses
The harmonic analysis involves the use of predictive computer software to identify potential harmonic problems and resolve mitigation solutions.
The Harmonic study shall consider operation during normal conditions, alternate operational
configurations, emergency power conditions and any other operations which could result in
harmonic distortion exceeding prescribed standards. It is important that these measurements be taken when your facility is operating at a minimum of 70% normal load.