Power quality can be defined as the comparison of voltage and current wave forms to their fundamental clean sinusoidal wave forms.
* Pure sine waves that are free from distortion are sometimes referred as 'Clean Power'
“Harmonic distortion is one of the main causes of the power quality problems”
* There are several types of voltage fluctuations that can cause problems, including surges and spikes, sags, harmonic distortion and momentary disruptions.
* Harmonics can cause sensitive equipment to malfunction and other problems, including overheating of transformers and wiring, nuisance breaker trips and reduced power factor.
Harmonic limitations have been established by IEEE 519 1992 for the following reasons:
* Where do harmonics come from? The general categories of harmonic producing loads (also called non-linear loads) are:
* Power electronic equipment (drives, rectifiers, computers, etc.)
* Arcing devices (welders, arc furnaces, florescent lights, etc.)
* Today, the most prevalent and growing harmonic sources are:
* Variable frequency drives (VFD)
* Switch-mode power supplies (SMPS - computers)
* Fluorescent lighting
* DC Drives and Motors
Signs of Harmonic Distortion Problems:
* Overheating of motors and transformers
* Frequent tripping of circuit breakers
* Frequent fuse blowing
* Capacitor failures
* Overloading of transformer neutrals
* Telephone interference
* Disoperation of motor variable-speed drives
* PLC and computer failures – “frozen” screens
* Electric component & Insulation failures severe lamp flicker
* Failure or malfunctioning of computers, motor drives, lighting circuits and other sensitive loads
The Power factor should always be LAGGING. PF should not LEAD.
Leading PF means over compensated than required.
Leading PF /Over compensation will adversely affect Lighting Systems, Machineries and Electronic Equipment. Under Certain conditions High Transient voltages may prevail on the power line - which is dangerous.
All the above details are being explained just to understand what Harmonics is in Electrical Distribution and Control System.