18-12-2012, 02:30 PM
RECENT TRENDS IN POWER SYSTEM
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ABSTRACT
The latest buzzword, in energy conscious industries, is the improvement of power quality. Good quality of electric power can not only result in handsome savings in power bills but also helps in avoiding unwarranted breakdowns.
This paper aims at analysing the reasons for poor quality of power and solutions for improving it. The change in magnitude and power factor can be corrected without much of difficulty with only problem being that of maintenance of shape, which is distorted by harmonics. We look at the factors causing in the production of harmonics, what impact these harmonics have on other equipments in the load serenity. We look at the types of harmonics, their effects and problems caused by them.
Active filters are the ultimate solution for reduction of harmonics which use the IGBT technology in additions to the pulse width modulation technology (PWM) which combines with control techniques to emerge successfully with improved power quality by fighting with the problems of harmonics to an extent that the THD (total harmonic distortion) is within acceptable limits i.e. <5%, these filters are the ultimate solution and far win over their counter parts i.e. passive filters.
REASONS FOR LIMITING HARMONICS
Harmonic pollution causes a number of problems. A first effect is the increase of RMS value and the peak value of distorted waveform. This is illustrated in the figure below (next page), which shows the increase of these values as more harmonic components are added to an initially undistorted waveform. The RMS-value and peak value of undistorted waveform are defined as 100%.
For example let us consider fundemental, 3rd, 5th harmonics with the help of the fig 1. in the next page. The increase of RMS-value increases heating of the electrical equipment. Furthermore, circuit breakers may trip due to higher thermal or instantaneous levels.
CONCLUSION
Considering all the above facts, it may not be surprising if electrical utilities across the country start penalizing industrial consumers for high harmonic levels like they do for poor power factor. This is because high harmonics are similar to poor power factor in terms of reducing the efficiency of power distribution system.
These days when industrial efficiency standards are being continuously improved, the concept of power quality management is going to play a very significant role in the near future. Thankfully there are qualified consulting engineering firms who should be able to help decide the right solution for a particular situation.