Detect and eliminate harmonics: why?: Difference between revisions

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'''Disturbances caused by harmonics'''
== Harmonic disturbances ==


Harmonics flowing in distribution networks downgrade the quality of electrical power. This can have a number of negative effects:
Harmonics flowing in distribution networks represent disturbances in the flow of electricity. The quality of electrical power is deteriorated, and the efficiency of the system is decreased.


*Overloads on distribution networks due to the increase in rms current
Here are the main risks linked to harmonics:
*Overloads in neutral conductors due to the cumulative increase in third-order harmonics created by single-phase loads
* Overload of distribution networks due to the increase of r.m.s. currents,
*Overloads, vibration and premature ageing of generators, transformers and motors as well as increased transformer hum  
* Overload of neutral conductors, which current can exceed the phase currents,
*Overloads and premature ageing of power-factor correction capacitors  
* Overload, vibration and premature ageing of generators, transformers and motors as well as increased transformer hum,
*Distortion of the supply voltage that can disturb sensitive loads  
* Overload and premature ageing of Power Factor Correction capacitors,
*Disturbances in communication networks and on telephone lines
* Distortion of the supply voltage that can disturb sensitive loads,
* Disturbance in communication networks and telephone lines.


'''Economic impact of disturbances'''
== Economic impact of disturbances ==


Harmonics have a major economic impact:  
All these disturbances have an economic impact:
* Premature ageing of equipment means it must be replaced sooner, unless oversized right from the start,
* Overload on the distribution network means higher equipment rating, increased subscribed power level for the industrial customer, and increased power losses,
* Unexpected current distortion can lead to nuisance tripping and production halt.


*Premature ageing of equipment means it must be replaced sooner unless oversized right from the start
== A necessary concern for the design and management of electrical installations ==
*Overloads on the distribution network can require higher subscribed power levels and increase losses
*Distortion of current waveforms provokes nuisance tripping that can stop production


'''Increasingly serious consequences'''
Harmonics are the result of the always expanding number of power electronic devices. They have become abundant today because of their capabilities for precise process control and energy saving benefits. Typical examples are Variable Speed Drives in the Industry, and Compact Fluorescent Lamps in commercial and residential areas.


Only ten years ago, harmonics were not yet considered a real problem because their effects on distribution networks were generally minor. However, the massive introduction of power electronics in equipment has made the phenomenon far more serious in all sectors of economic activity.  
International standards have been published in order to help the designers of equipment and installations. Harmonic emission limits have been set, so that no unexpected and negative impact of harmonics should be encountered. In parallel to a better understanding of effects, solutions have been developed by the Industry.


In addition, the equipment causing the harmonics is often vital to the company or organisation.
Harmonic consideration is now a full part of the design of electrical installations.
 
'''Which harmonics must be measured and eliminated?'''
 
The most frequently encountered harmonics in three-phase distribution networks are the odd orders. Harmonic amplitudes normally decrease as the frequency increases. Above order 50, harmonics are negligible and measurements are no longer meaningful. Sufficiently accurate measurements are obtained by measuring harmonics up to order 30.
 
Utilities monitor harmonic orders 3, 5, 7, 11 and 13. Generally speaking, harmonic conditioning of the lowest orders (up to 13) is sufficient. More comprehensive conditioning takes into account harmonic orders up to 25.

Latest revision as of 09:48, 22 June 2022

Harmonic disturbances

Harmonics flowing in distribution networks represent disturbances in the flow of electricity. The quality of electrical power is deteriorated, and the efficiency of the system is decreased.

Here are the main risks linked to harmonics:

  • Overload of distribution networks due to the increase of r.m.s. currents,
  • Overload of neutral conductors, which current can exceed the phase currents,
  • Overload, vibration and premature ageing of generators, transformers and motors as well as increased transformer hum,
  • Overload and premature ageing of Power Factor Correction capacitors,
  • Distortion of the supply voltage that can disturb sensitive loads,
  • Disturbance in communication networks and telephone lines.

Economic impact of disturbances

All these disturbances have an economic impact:

  • Premature ageing of equipment means it must be replaced sooner, unless oversized right from the start,
  • Overload on the distribution network means higher equipment rating, increased subscribed power level for the industrial customer, and increased power losses,
  • Unexpected current distortion can lead to nuisance tripping and production halt.

A necessary concern for the design and management of electrical installations

Harmonics are the result of the always expanding number of power electronic devices. They have become abundant today because of their capabilities for precise process control and energy saving benefits. Typical examples are Variable Speed Drives in the Industry, and Compact Fluorescent Lamps in commercial and residential areas.

International standards have been published in order to help the designers of equipment and installations. Harmonic emission limits have been set, so that no unexpected and negative impact of harmonics should be encountered. In parallel to a better understanding of effects, solutions have been developed by the Industry.

Harmonic consideration is now a full part of the design of electrical installations.

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