Download Power quality: Innovation in harmonic filtering

Power Quality
Innovation in Harmonic Filtering
ABSTRACT:
the Basic concept of harmonics, their
generation, problems created by
great
Power quality has become a
them
concern
FILTERATION as a solution for
suppliers
because
for
and
the
both
their
energy
customers
increasing
use
and
HARMONIC
this problem of Harmonics.
of
sensitive devices and the significant
consequences
of
a
poor
power
INTRODUCTION:
quality for the competitiveness of the
“POWER
companies.
QUALITY”
is
The increasing developments
defined as “the concept of powering
need increasing use of electricity.
and grounding electronic equipment in
While meeting this power demand,
a manner that is suitable to the
there causes a pollution in electrical
operation of the equipment ina manner
system
The
that is suitable to the operation of that
harmonics are integer multiples of
equipment and compatible with the
fundamental
premise wiring system
called
Harmonics.
currents/voltages.
Substantial presence of harmonics
and other
connected equipment.
results in excessive overheating of
the equipments and other problems.
power quality has become a strategic
Harmonics are created by non linear
issue for the following reasons:
loads that draw current in abrupt

The economic necessity for
pulses rather than in a smooth.
businesses to increase their
Different problems due to harmonics
competitiveness.
have different solutions.
In this
paper we are going to present you

The
widespread
use
of
equipment which is sensitive to

voltage disturbances and /or
the voltage magnitude at a point in the
generates disturbances itself.
electric
The
deregulation
of
the
System and lasting from 0.5 cycles to
electricity market.
few
seconds.
Either
In this context, it is essential for
operations or any type of faults as well
the utility and the customers to prevent
as fault clearing process can cause a
and detect power quality problems and
voltage dip. Switching like those
to have solutions available to fix them.
associated
The power quality correction and
disconnection of the supply or flow of
harmonic filtering system give solution
heavy currents associated with the
to solve the problems of harmonic
starting of large motor loads is the
disturbances and voltage fluctuations.
most common. These events maybe
with
a
switching
temporary
originated at the utility side or at the
customer site.
MAIN
POWER
QUALITY
VOLTAGE
VARITIONS
AND
FLUCTUATIUONS:-
DISTRUBENCES:
Voltage variations are variations in the
Power
quality
characterising
usually
low
conducted
involves
frequency
electromagnetic
disturbances which can be ranked in
rms value or the peak value with
amplitude of less than 10% of the
nominal voltage. Voltage variations are
a series of voltage changes which are
characterised by the frequency of
different categories.
variation and the magnitude.
Voltage variations are caused by a
VOLTAGE SAG:Voltage
sag
is
a
sudden
reduction (between 10% and 90%) of
slow variation of loads
current wave shapes, which in turn
cause harmonic currents to flow, back
into other parts of the power system.
Consumers Generating Harmonics:
Harmonics are not generated by
connected to the network and mainly
power generators but are produced by
due to rapidly varying industrial loads
Non-linear loads as under:
such as welding machines.
Loads that make use of semi conductor
devices
HARMONICS:-
like transistor, thyristor i.e., static
Harmonics are currents or voltages
rectifiers.
with frequencies that are integer
using
multiples of the
converters, static inverters like:
-
(AC/DC conversion
SCRs),
static
frequency
Static Power converters (AC –
DC conversion using SCRs)
-
Static rectifiers
-
Static frequency converter
-
Static
power
supplies
fundamental power frequency. The
fundamental frequency itself is called
-
as the first Harmonic.
i)
The second
uninterrupted
Static induction regulators.
Variable impedance loads,
Harmonic as frequency twice that of
using
the fundamental, the third Harmonic
furnaces,
has frequency thrice that of the
Fluorescent
fundamental and so on. For example –
discharge
if the fundamental frequency is 50Hz
control, brightness etc.,
then the second Harmonic is 100 Hz,
the third Harmonic is 150Hz etc.
ii)
electric
Loads
welding
magnetizing
inductance,
Harmonics are created by non-linear
reactors etc.,
manner. These pulses cause distorted
units,
tubes,
using
Generation of Harmonics:-
rather than in a smooth sinusoidal
are
lamps,
saturated
loads that draw currents abrupt pulses
arcs,
light
strong
currents,
Transformers,
furnaces,
Office
automation
equipment
like
AC Filters: These are shunt connected
computers, UPS, printers and fax
AC
machine etc.,
connected between AC busbars and
PROBLEMS
DUE
TO
LOW


Damaging
of
computer
filters.
They
are
earth. They offer low impedance to
harmonic
POWER QUALITY:

harmonic
frequencies
and
high
impedance to power frequency. Thus,
hardware and memory.
harmonic frequencies are passed to
Motors fail to start due to low
earth and are eliminated from the AC
voltages
network.
Setting
and
resetting
of
electronic equipments will be
out of control .

Industrial and domestic loads
will get damaged.
Solution to Harmonic Distortion:
Harmonic Filtration:
Harmonics in AC & DC waveforms
are minimized by following means:
1. Use of DC smoothing reactor.
2. Use of DC harmonic filters.
3. Use of AC harmonic filters.
DC Smoothing Reactor: This is oil
cooled, oil insulated reactor having
high inductance (0.35H to 1H).It is
connected in series on the DC side of
the converter. It smoothen the ripple in
the DC current. The DC reactor also
AC shunt filters serve dual purpose
on AC side:
1. They divert harmonics to earth
and
reduce
the
harmonic
contents in main AC network.
2. They
provide
shunt
compensation required on AC
side for satisfactory converter
operations.
helps in reducing the rate of rise of
current surges appearing on the DC
side of the converter due to sudden
changes in DC power flow due to
faults or load change.
CLASSIFICATIONS
OF
AC
SHUNT FILTERS: Tuned AC shunt filters are used for
suppressing lower order characteristic
harmonics eg. Separate tuned branches
for 5th, 7th, 11th, 13th harmonics. These
branches may be either single tuned for
of a double tuned AC shunt
each
characteristic
filter consists of a RLC series
frequency or each branch double tuned
circuit in series with another
for two frequencies eg. 5th/7th, 11th/13th,
L2, C2, & R3, L3 parallel circuit.
23rd/25th, 3rd/36th etc.,
The values are selected such
Tuned AC shunt filters are classified
that the total filter has two
into two types.
resonant
of
the
above
a) A Single frequency tuned
Shunt filters is a single RLC
series
circuit
frequencies
(One
given by CLL2C2 & other by
CR3 L3).
connected
between a phase and earth.
The filter is tuned to one
particular
characteristic
harmonic frequency. Separate
branches are necessary for each
lower characteristic harmonic
frequency. The filter is tuned
to
the
resonates
frequency
equal to the corresponding
characteristic harmonic order.
1) High pass filter branches are
arranged
to
suppress
harmonics of higher order say
24th & above. With High pass
AC
shunt
harmonic
filter
connected near AC Bus bars,
all the higher harmonics are
diverted to earth and are not
allowed to proceed to the AC
Network.
b) A Double frequency tuned
shunt filters has two resonant
th
th
rd
resonant
frequencies, the circuit of the
double
tuned
filter
is
th
frequencies eg. 5 / 7 , 11 /
th
At
equivalent
to
two
parallel
th
13 , 3 /36 . A typical circuit
single tuned branches.
A
double frequency tuned filter
Harmonic currents & voltage
has lowest impedance at two
distortion are becoming the most
resonant frequencies.
severe
filters
are
also
These
called
as
Damped Filters.
and
complex
electrical
challenge for the electrical industry.
So by designing and giving complete
solutions in the form of detuned and
tuned harmonic filter systems, Active
DC Harmonic Filters
DC filters are designed to
filters and other protection systems for
reduce DC harmonics to minimize the
industrial installation that can ensure
telephone
the trouble free operation of electrical
interference
in
voice
frequency range (100Hz to 5 KHz). In
installation for industries.
addition to the telephone interference
By defining and implementing these
criterion, the DC filter is designed with
solutions users will be provided with
interior of avoiding the resonance
the right quality of power supply for
between DC filters & DC line at lower
their requirements .
order harmonics.
CONCLUSION:
Power quality has become a
strategic issue for consumers. In this
present
economic
context,
the
consequences of electrical disturbances
become more and more serious.