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Disturbances caused by harmonics | '''Disturbances caused by harmonics''' | ||
Harmonics flowing in distribution networks downgrade the quality of electrical power. This can have a number of negative effects: | |||
Harmonics flowing in distribution networks downgrade the quality of electrical power. This can have a number of negative effects: | |||
*Overloads on distribution networks due to the increase in rms current | |||
*Overloads in neutral conductors due to the cumulative increase in third-order harmonics created by single-phase loads | |||
b Distortion of the supply voltage that can disturb sensitive loads | * Overloads, vibration and premature ageing of generators, transformers and motors as well as increased transformer hum | ||
*Overloads and premature ageing of power-factor correction capacitors b Distortion of the supply voltage that can disturb sensitive loads | |||
Economic impact of disturbances | *Disturbances in communication networks and on telephone lines | ||
Harmonics have a major economic impact: | |||
'''Economic impact of disturbances''' | |||
'''Harmonics have a major economic impact:''' | |||
Increasingly serious consequences | |||
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. | *Premature ageing of equipment means it must be replaced sooner unless oversized right from the start | ||
In addition, the equipment causing the harmonics is often vital to the company or organisation. | *Overloads on the distribution network can require higher subscribed power levels and increase losses | ||
Which harmonics must be measured and eliminated? | *Distortion of current waveforms provokes nuisance tripping that can stop production | ||
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. | '''Increasingly serious consequences''' | ||
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. In addition, the equipment causing the harmonics is often vital to the company or organisation. | |||
'''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. | |||
Revision as of 09:14, 10 February 2010
Disturbances caused by harmonics
Harmonics flowing in distribution networks downgrade the quality of electrical power. This can have a number of negative effects:
- Overloads on distribution networks due to the increase in rms current
- Overloads in neutral conductors due to the cumulative increase in third-order harmonics created by single-phase loads
- Overloads, vibration and premature ageing of generators, transformers and motors as well as increased transformer hum
- Overloads and premature ageing of power-factor correction capacitors b Distortion of the supply voltage that can disturb sensitive loads
- Disturbances in communication networks and on telephone lines
Economic impact of disturbances
Harmonics have a major economic impact:
- Premature ageing of equipment means it must be replaced sooner unless oversized right from the start
- 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
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. In addition, the equipment causing the harmonics is often vital to the company or organisation.
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.
