POWER HARMONICS- SOURCES, ISSUES AND MITIGATION

1
POWER SYSTEM HARMONICS:
SOURCES,ISSUES AND MITIGATION
Presented by-
ASHIK.S & ROOPESH.R.NAIR
AMMINI COLLEGE OF ENGINEERING

HISTORY OF HARMONICS
 Power system have always had harmonics present.
 In early 1890’s harmonics were associated with distorted current and
voltage waveform shape on transmission system.
 Over the last fifteen years, the proliferation of electronic device has
brought subject up-front and personal.
 As the number of electronic devices increased, so did the number of
other harmonics creating devices.
 There has been an explosion of microprocessor based equipment which
are also non-linear loads. Examples include computer systems, variable
frequency drives, AC/DC converters, electronic ballasts, X-ray machines,
MRI equipment.
2
ASHIK.S AND ROOPESH.R.NAIR, AMMINI COLLEGE OF
ENGINEERING

LINEAR LOADS
 Linear loads occur when the impedance is constant; then the
current is proportional to or the same as the voltage
 A linear element in a power system is a component in which the
current is proportional to the voltage.
 Typical linear loads are incandescent lights and motors, heaters
ENGINEERING
3

NON-LINEAR LOADS
 Non linear loads occur when the impedance is not constant; then
the current is not proportion or the same as the voltage.
 The current drawn by non-linear loads is not sinusoidal but is
periodic, meaning that the current wave looks the same from cycle
to cycle
 Typical non-linear loads are electronic switch mode power supplies,
DC/AC drive and induction furnace/arc furnace.
 There are basically two types of non-linear loads: single phase and
three phase.
ENGINEERING
4

CAUSES OF HARMONICS?
 Harmonics are created by a non-linear loads that draw a current in
abrupt pulses rather than a smooth sinusoidal manner.
 Harmonic resonance occurs when the capacitor reactance and the
system reactance are equal.
 All electronic loads generate positive & negative sequence harmonic
currents, single phase electronic loads connected phase neutral in a
3 phase 4wires distribution system, also generate zero sequence
harmonic currents
 Appliances:
 TV set, air conditioners, washing machines, microwave ovens and
vacuum cleaners.
 Fax machines, photocopies, printers and so on.
ENGINEERING
5

SOURCES OF HARMONICS
☞ Adjustable drive systems
☞Arc Furnaces
☞Switching Mode Power Supplies
☞Computers, TV sets
☞HVDC Transmission
☞Electric Traction
☞Wind & Solar power generation
☞Battery charging & Fuel cells
☞Fluorescent lighting, Electronic ballasts…
ENGINEERING
6

EFFECTS OF HARMONICS
☞ Increased Cu loss leading to Excessive heating.
☞Harmonic Torques.
☞Voltage distortion in weak system.
☞Harmonic voltages increase hysteresis and eddy current losses, also
additional 𝐼2R losses mainly in Converter transformers.(Transformer
derating).
☞Power factor also deteriorates.
☞Phenomenon of Flicker.
ENGINEERING
7

☞Excessive neutral currents.
☞Effects measuring instruments.
☞Misoperation of relays.(False tripping of ground relay due to
triplen harmonics)
☞Parallel resonance between Cable capacitance and system
inductances, incase of long cables.
☞Introduces Electromagnetic interference in adjacent signal or
control cables via radiated and conducted emissions.
ENGINEERING
8

PROBLEMS DUE TO HARMONICS
 Large load currents in the neutral wires of a 3 phase system.
 Overheating of standard electrical supply transformers which
shortens the life of a transformer and will eventually destroy it.
 High voltage and current distortion exceeding
 Poor power factor conditions result in monthly utility penalty
fees for major users (factories, manufacturing and industrial)
with a power factor less than 0.9.
 Resonance that produces over-current surges.

ENGINEERING
9

 False tripping of branch circuit breakers.
 Waste energy/high electric bill
 Capacitors: can be affected by heat rise increases due to power loss and
reduced life on the capacitors.
ENGINEERING
10

MITIGATION
ENGINEERING
11

 There are many ways to reducing harmonics. The primary
methods used today to reduce harmonics are:
 Power System design: harmonics can be reduced by
limiting the non-linear load to 30% of the maximum
transformer’s capacity.
 Isolation transformers: An isolation transformer provides a
good solution in many cases.
ENGINEERING
12

METHODS TO MITIGATE
HARMONICS
1.Passive filters.
2.Active filters.
Filters are used to suppress harmonics as well as to support reactive
power.
3.Operation with higher pulse number.
4.Using K-factor transformers.
ENGINEERING
13

PASSIVE FILTERS
 1.Single tuned filter:
Based on series resonance of RLC circuit. The circuit is
designed to resonate at the frequency equal to the frequency
of the component which needs to be filtered.
It is confined to a particular frequency.
ENGINEERING
14

2.Double tuned filter:
This filter is tuned to two frequencies equal to the frequency of the
significant harmonic components in the magnitude spectrum.
ENGINEERING
15

3.High pass filters:
These filters are designed such that all the components of frequencies
higher than a particular frequency are filtered.
• Passive filters are cheap, easy design and reliable.
• But they cause resonance problems, fixed reactive power
compensation and large size.
ENGINEERING
16

ACTIVE FILTERS
 Active power filters are Power electronic converters to inject
harmonic currents into the system.
 They can eliminate voltage and current harmonics;
compensate for reactive power. No resonance problems, can
support variable reactive power compensation. Expensive,
complex control.
ENGINEERING
17

 New generation of harmonic filters
 Very high Speed IGBT ensuring response time of a few milliseconds
 Capable of generating wide spectrum of harmonic currents to
inject into the network to cancel the harmonic current drawn from
the source by nonlinear loads
 Additionally they can generate both capacitive and inductive
reactive power in a step-less manner improving the PF of the load.
ENGINEERING
18

ENGINEERING
19

ENGINEERING
20
ACTIVE FILTERING
Parallel type Series type

HYBRID FILTERS
 A combination of passive and Active filter
 Active filters are used to handle the dynamically varying harmonic
component and passive filters handle more predictable narrow
band in addition to providing capacitive reactive power
compensation at fundamental frequency.
ENGINEERING
21

ENGINEERING
22

ENGINEERING
23
 Hybrid of series active and parallel passive
 Hybrid of parallel active and series passive

CONCLUSION
 It is essential to know the effects of the harmonics, sources of
the harmonics for a power engineer to ensure that the systems
will work well within the safety zone, owing to standards.
 Also, the various harmonic mitigation techniques discussed are
to be understood well for a design engineer to protect the power
system from harmonics.
ENGINEERING
24

REFERENCES
☞Power system Harmonics- Jos Arrillaga, Neville R. Watson.
☞Control of Harmonics in Electrical Power systems,
from American Bureau of Shipping(ABS).
☞POWER SYSTEM ANALYSIS, Short circuit load flow and
Harmonics-J. C. Das
☞IEEE transactions on Power Apparatus & Systems, Power
system Harmonics: An Overview, Vol.PAS-102, No.8,
August1983.
ENGINEERING
25

☞ IEEE transactions on Power Apparatus & Systems, vol.PAS-104,
No.9, 1985. The effects of Power system Harmonics on Power
system equipment and Loads.
☞Mitigation of Harmonics in a Neutral Conductor for Three-
Phase Four-Wire Distribution System using Series Active
Power Filter 2015 IEEE paper
☞A Review of Harmonic Mitigation Techniques –by Gonzalo
Sandoval & John Houdek, © 2005
☞Harmonic Mitigation In Minigrid Integrated Distributed
Power System-2016 International Conference on Circuit, Power
and Computing Technologies [ICCPCT]
ENGINEERING
26

THANK
YOU
ASHIK.S AND ROOPESH.R.NAIR, AMMINI COLLEGE OF ENGINEERING 27

POWER HARMONICS- SOURCES, ISSUES AND MITIGATION

More Related Content

POWER HARMONICS- SOURCES, ISSUES AND MITIGATION