HARMONIC ANALYSIS AND CALCULATION"

HARMONIC ANALYSIS AND CALCULATION

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
	Photocopiers
	Printers
	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.