21-06-2011, 11:40 AM
PRESENTED BY:
S.M.JAFFER
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HARMONICS AND THEIR EFECTS ON POWER SYSTEM
Seminar Flow
Why we need to study harmonics.
What are harmonics
How are they generated
What effect these harmonics have.
What are the measures to counter them.
Why study Harmonics
Presence of harmonics in the power system severely affects its operation and stability.
Everyday more and more no. of non-linear loads are being connected to the power system.
Harmonics have the potential to disrupt or outright destroy the power system under right conditions.
Overall power efficiency, quality and reliability are affected.
Cost of power to consumers increases due to metering difficulties in presence of harmonics.
When dealing with such a large system small disturbances cannot be allowed to prevail as they can easily lead to very large catastrophes.
HARMONICS
Harmonics are those voltage or current signals which have frequency as the integral multiple of the power frequency.
Any distorted periodic waveform can be broken into signals which are harmonics of the power signal.
This treatment to the distorted waveform is done using Fourier theorem.
In power System usually symmetric harmonics are generated, i.e. they are all odd harmonics of the fundamental power frequency.
GENERATION OF HARMONICS
GENERATORS
They possess distributed windings on stator and field windings on rotor.
Air gap flux in not perfectly symmetric due to odd symmetry of poles.
Distribution of windings is not perfect around the stator inner periphery.
