In this ppt we will get to know about basic idea of harmonics, types of harmonics , measuring devices and minimizing techniques and also covering the there impact on power system and impact on consumer equipment's.

1. IDENTIFICTION & MINIMIZATION
OF
HARMONICS
MR. MAYUR S HIWALE

2. HARMONICS
 Distortion Or Deviation Of Prefect Sinusoidal Waveform Is Called
HARMONICS
OR
 Currents Or Voltages With Frequencies That Are Integer
Multiples ( H=0,1,2,…N) Of The Fundamental Power Frequency
is HARMONICS
1st harmonic: 50Hz
2nd harmonic: 100Hz
3rd harmonic: 150Hz

3. CONCEPT
Imagine a power system with an AC source and an electrical load
Figure - Power System with AC source and electrical load
 Load are of two types linear load or non linear load
 Linear loads are induction motor, heaters and incandescent lamps etc.
 Non linear loads are electronic loads such as diode, thyristors, Fluorescent
lighting, converts etc.

4.  Type of Load affect the power quality.
Linear loads draw current that is sinusoidal in nature so they generally do
not distort the waveform as shown in figure 1
Figure 1: Ideal Sine wave (current drawn by linear load)

5. Non-linear loads, however, can draw current is not perfectly
sinusoidal (Figure ).
 Since the current waveform deviates from a sine wave, voltage
waveform distortions are created.
Figure 3: Distorted Waveform

6. Production of harmonics
 Power system harmonics: presenting deviations from a perfect
sinusoidal-waveform (voltage or current waveform).
 The distortion comes from a Nonlinearity caused by saturation,
electronic-switching and nonlinear electric loads,
Figure3 - production of harmonics

7. Why Bother about Harmonics?
50-60% of all electrical Ac Systems in INDIA operate with non-
linear type loads
Power-Quality-PQ Issues & Problems
Damage to Power Factor Correction capacitors
Waveform Distortion can create
SAG/SWELL/NOTCHING/RINGING
All can cause damage effects to consumer loads and power
systems due to Over-Current/Over-Voltage or Waveform Distortion
Additional Power/Energy Los

8. Loads Producing Harmonic
Electronic lighting ballasts/Controls
Adjustable speed Motor-Drives
Electric Arc Welding Equipment
Solid state Industrial Rectifiers
Industrial Process Control Systems
Uninterruptible Power Supplies ( UPS )systems
Saturated Inductors/Transformers
LAN/Computer Networks

9. IDENTIFICATION OF HARMONIC IN SYSTEM
 Theoretical methods
 Harmonic Power Flow Direction Method
 Load Impedance Variation Method
 On-Line Impendence Measurement
 Neural Network Based Method
 Signal Processing Based Techniques

10. Analysis of harmonics

11. Calculation of THD
 Total harmonic distortion, or THD is a common measurement of the level
of harmonic distortion present in power systems.
 THD is defined as the ratio of total harmonics to the value at
fundamental frequency.
where Vn is the RMS voltage of nth harmonic and n = 1 is the
fundamental frequency

12. Effects of Harmonics
 Overheating and premature failure of distribution transformers
Increasing iron and copper losses or eddy currents due to stray
flux losses
 Overheating and mechanical oscillations in the motor-load system
Producing rotating magnitude field, which is opposite to the
fundamental magnitude field.
 Overheating and damage of neutral ground conductors
 Trouble sustained type Harmonics: 3rd, 9th, 15th …
 A 3-phase 4-wire system: single phase harmonic will add rather
than cancel on the neutral conductor

13.  Malfunction/Mal-Operation of Sensitive Tele-control and Protection
Relaying
 False or spurious Relay operations and trips of circuit breakers
 Failure of the Firing/Commutation circuits, found in DC motor-drives
and AC drives with silicon controlled rectifiers (SCR-Thyristor)
 Mal-Operation instability of voltage regulator

14. Power factor correction capacitor failure
Reactance (impedance)-Zc of a capacitor bank decreases as the
frequency increases.
Capacitor bank acts as a sink for higher harmonic currents.
The System-Series and parallel Resonance can cause dielectric
failure or rupture the power factor correction capacitor failure due to
Over-Voltages & Over-Currents.

15. Measuring Equipments for Harmonics
 Digital Oscilloscope:
Wave shape, THD and Amplitude of each harmonic
 True RMS Multi-Meter:
Giving correct readings for distortion-free sine waves and typically
reading low when the current waveform is distorted
Figure 4: “True RMS” Multi-Meter

16. Minimization of harmonics
An L-C filter consists of a capacitor bank and an induction coil. The filter is
designed or tuned to the predetermined non-linear load and to filter a
predetermined harmonic frequency range. This is connected in parallel to
the non-linear load with the objective of filtering the major harmonics
generated by the non-linear load. This application is mostly used when
specified for a UPS or variable frequency drive motor in a manufacturing
plant.
 L-C Filter

17.  Active Power Filter
The active power filter (AFP) is a device that is connected in system to
cancels the reactive and harmonic currents from a group of nonlinear loads
so that the resulting total current drawn from the ac main is sinusoidal.
Ideally, the APF needs to generate just enough reactive and harmonic current
to compensate the nonlinear loads in the line, thus it handles only a fraction
of the total power to the17 load.
The performance of this active power filter depends on the inverter
topologies and the PWM control method .Therefore, the suitable device in
developing the AFP is “Pulse Width Modulated (PWM)” inverter by using
IGBT or MOSFET devices. There are two kinds for active power filter such as
series and shunt filters.

18.  Phase Shifting
A harmonic minimizing using transformer is a new power quality product
for minimizing harmonic problems in electrical distribution systems.
This type of transformer has patented built-in electromagnetic
technology designed to remove the most harmful harmonics from the 3rd
through 21st.
The technique used in these transformers is call phase shifting . These
transformers can be used to reduce existing harmonics in line current
system. This same application can be designed into new construction to
prevent future harmonics problems.

19. Conclusion
The harmonic distortion principally comes from Nonlinear-Type Loads.
The application of power electronics is causing increased level of
harmonics due to Switching!!
Harmonic distortion can cause serious Failure/Damage problems.
Harmonics are important aspect of power operation that requires
Mitigation!!
Over-Sizing and Power Filtering methods are commonly used to limit
Overheating Effects of Sustained Harmonics.