IEEE - International Conference On Advances In Engineering, Science And Management (ICAESM -2012) March 30, 31, 2012 596
in modern electrical networks. Problems in
computers due to poor power quality are
Damage to computer chips, causes
computer downtime, computer errors etc.,
UPS system do not address transient
problems effects
Poor power quality can cut the lifetime of
motor to half.
The distorted current is a result of several sine
wave currents at mUltiples of fundamental
frequency. These high frequency components
are called as 'Harmonics'. When the harmonic
currents flow through the power distribution
system, harmonic voltages are developed.
These harmonic voltages are superimposed over
the incoming pure supply voltage causing
distortion in the voltage. Since voltage is
common to all loads (linear or non-linear),
harmonic distortion spreads in the electrical
system causing varying degree of damage
depending upon the susceptibility and sensitivity
of the electrical equ ipment.
SOURCES OF HARMONICS
Switched mode power supplies (SMPS)
Electronic fluorescent lighting ballets
Variable speed drive
Uninterrupted power supply (UPS)
Magnetic cored devices.
Power converters and rectifiers
Electric arc furnaces and welders
Induction furnace
ClTransformer magnetization non-linearity
An industrial unit generating harmonics becomes
a source of pollution not only for itself but also
other power consumers within its vicinity.
HARMONICS
1) Types:
a) Less then fundamental (sub harmonics)
b) Greater than fundamental
a) Multiple of fundamental harmonics i.e. odd
& even
b) Non-multiple of fundamental (Inter
harmonics)
[Fundamental harmonics
50 Hz ±...l.Hz (normally)
50 Hz ± 3 Hz (exited)]
2) Nature of Occurrence
a) Steady
b) Intermittent
3) Effects
A) NUISANCE
i) Communication noise.
ii) Light flickers
iii) T.V. interference