Real time distribution factor meter for non linear loads

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DEPARTMENT OF ELECTRICAL ENGINEERING

FINAL YEAR PROJECT THESIS

REAL TIME DISTRIBUTION FACTOR

METER FOR NON LINEAR LOADS

BY

Moiz Ahmed Rana BSEE01093080R

Sultan Zahoor BSEE01093041

Muhammad Ashfaq BSEE01103161

Ghulam Mustafa BSEE01113156

Advisor: Hafiz Tehzeeb ul Hassan

This thesis is submitted to The University of Lahore, Pakistan, for partial

fulfillment of the requirements for the degree of Bachelor of Science in

Electrical Engineering.

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DEDICATION Dedicated to our beloved parents and family who provided us every opportunity to achieve our

goals and whose prayers resulted in the completion of this project and to our teachers who tried

the level best to convey us the knowledge they had.

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DECLARATION We declare that the work submitted in this report is our own and any help taken from authenticated

sources is duly referenced.

Moiz Ahmed Rana BSEE01093080R

Sultan Zahoor BSEE01093041

Ghulam Mustafa Tabassam BSEE01113156

Mohammad Ashfaq BSEE01103161

June 2015

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CERTIFICATE OF APPROVAL It is to certify that this project has been done under my supervision by this group having title Real

time distribution factor meter for non linear loads the end result is from the original work done

by the group members and, to the best of my knowledge, is not aided by any unfair means. The

members tried their best to prepare this report.

Signature of project advisor: ____________________

Dated: ____________________

Signature of Head of Department: ____________________

Dated: ____________________

Institute: The University of Lahore

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ACKNOWLEDGMENT We would first like to thank our parents for all the support they have given us throughout our

University time and everything before.

We would like to thank our respected advisor Hafiz Tehzeeb ul Hassan for his help and guidance

throughout the course of the project.

Special thanks to all our friends for helping us with conducting tests. We would like to extend our

appreciation to our colleagues who share their knowledge and experiences. Without them this

project would be a failure.

In addition we like to thanks those who support direct and indirectly in any respect during the

completion of the project.

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TABLE OF CONTENTS

Abstract.11

Chapter # 1 Introduction12

1.1 Problem statement..12

1.2 Objectives..12

Chapter # 2 Basic concepts........................................................14

2.1 Linear loads..14

2.2 Non linear loads...15

2.2.1 Characteristics of non linear loads........................................................15

2.2.2 Effects of non linear loads on power system16

2.2.3 Comparison between linear and non linear loads.17

2.3 Power factor.17

2.3.1 Causes.......................................................17

2.3.2 Disadvantages of low power factor...18

2.3.3 Power factor for linear loads.18

2.3.4 Power factor for non linear loads..19

2.3.5 Power factor correction for linear loads20

2.3.6 Power factor correction for non linear loads.20

2.4 Harmonics21

2.5 Distortion factor...21

2.6 Design recommendations for systems having harmonics22

2.7 Treatment for harmonic problems.......................................................23

Chapter # 3 Design and working...24

3.1 Current and voltage measurement.......................................................25

3.2 Power measurement.27

3.3 Power factor measurement.......................................................28

3.4 Distortion factor measurement.29

Chapter # 4 Electrical components32

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4.1 Current transformer32

4.2 Potential transformer..33

4.3 Zero crossing detector.34

4.4 B380 (Bridge rectifier).36

4.5 Power supply circuit36

4.6 LM7805 (Voltage regulator)37

4.7 LCD display.37

4.8 Load.38

Chapter # 5 Microcontroller.......................................................40

5.1 Overview..40

5.2 Working of microcontroller.41

5.2.1 Algorithm for current and voltage measurement..42

5.2.2 Algorithm for power measurement...43

5.2.3 Algorithm for power factor measurement.44

5.2.4 Algorithm for distortion factor measurement...46

5.2.5 LCD initialization.49

Chapter # 6 Conclusion..54

6.1 Results..54

6.2 Future Work.55

References..56

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LIST OF FIGURES

2.1 Linear load waveform......15

2.2 Non linear load waveform.......................................................16

2.3 Power triangle..19

2.4 Third harmonic effect..22

3.1 Main stages..24

3.2 Current and voltage measurement.......................................................26

3.3 Power measurement.27

3.4 Power factor measurement.......................................................28

3.5 Distortion factor measurement.29

3.6 Complete layout.......................................................31

4.1 CT circuit.32

4.2 Potential transformer33

4.3 PT circuit..34

4.4 Zero crossing explanation35

4.5 Zero crossing detector..35

4.6 B380.36

4.7 Power supply circuit36

4.8 LM780537

4.9 LCD Display38

4.10 Load...39

5.1 PIC pin configuration.......................................................40

5.2 Algorithm for current and voltage measurement.....42

5.3 Algorithm for power measurement..43

5.4 Algorithm for power factor measurement45

5.5 Algorithm for distortion factor measurement..47

5.6 LCD and microcontroller interface..53

6.1 Phase 1 Results54

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6.4 Power factor and distortion factor...55

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LIST OF TABLES

2.1 Comparison of linear and non linear loads..17

4.1 CT circuit simulation results33

4.2 PT circuit simulation results34

4.3 LCD pin configuration.37

5.1 PIC characteristics...41

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ABSTRACT

Our project named Real time distribution factor meter for non linear loads is a three phase meter

which measures the distribution factors for non linear loads. By distribution factor, we mean all

the factors which are involved in power distribution. They are current, operating voltage, power

being consumed, power factor and the harmonic distortion factor. The meter focuses essentially

on the non linear loads. The purpose for focusing on non linear loads is because the majority of

the loads installed in industries and homes is non linear. Non linear loads are those loads which do

not follow Ohms Law. They include mostly inductive and capacitive loads. These kinds of loads

have power factor issues and they generate serious amount of harmonics and noise. There is a need

to check and monitor these issues. This is the main objective and motivation behind this project.

We have approached the problem by first measuring the current and voltage of the load by means

of current and potential transformers. These quantities are fed to the microcontroller which

calculates the distribution factors. The microcontroller which we selected is PIC18F452. The

reason was its reasonable price and the features like ADC, USART and other functions.

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CHAPTER # 1

INTRODUCTION

1.1 PROBLEM STATEMENT Large industries and electrical utilities are very concerned about the presence of non linear loads

in their electrical power systems.

Power systems that are conceived to operate at the fundamental frequency are prone to abnormal

behavior as more and more nonlinear loads are connected to the network. Harmonics increase the

resistances of the conductors due to skin effect and cause an abnormal neutral-ground voltage

difference. The more nonlinear loads connected, the higher the overall sum of harmonics, though

the total sum is less than the sum of the individual magnitudes. Harmonics can damage components

like fuses and circuit breakers, and can cause utility meters to record wrong measurements.

There is great concern about the distribution transformers that supply the nonlinear loads, since

they suffer from:

1. Overheating of windings, insulation, and oil

2. Additional eddy current heating in metallic parts

3. Higher stress in tap changers, bushings, and cable end connections

This project is a three phase meter which displays the following parameters:

1. Current

2. Operating voltage

3. Power being consumed

4. Power factor

5. Distortion factor

1.2 OBJECTIVES

To determine the distribution factor of non linear load.

Non linear load distribution includes changing current magnitude required by the non linear

load

Distribution factor measurement also includes the changing voltage needs of non linear

load.

It also includes the measurement of determination of the distortion occurred due to non

linearity in the actual sine wave provided to the load by the system.

Determining the power factor of the non linear load that is provided.

Determining the overall changing behavior and needs of the non linear load .

Determining all the factors in one place that affect the consumption needs of the non linear

loads.

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Determining all these factors and putting them in perspective according to the project

requirement

At last combining these factors together to apply a solution of the damage caused by the

non linearity.

To determine certain techniques so that the non linearity does not affect the overall system

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CHAPTER # 2

BASIC CONCEPTS

Generally the loads installed in homes and in the industries are of two types. Linear and non-linear.

In this section, we shall describe the difference between linear and non-linear loads. Their

characteristics, behavior, effect on the power system and their examples will be discussed.

2.1 LINEAR LOADS

In linear loads, the output response is directly proportional to that of input. In the case of AC, it

means that the application of a sinusoidal voltage results in a sinusoidal current. As the

instantaneous voltage changes over the period of sine wave, the instantaneous current which rises

and falls in proportion to the voltage so that the waveform of the current is also a sine wave. The

current at any time is proportional to voltage and these loads does not change the shape of the

waveform of the current, but may change the relative timing (phase) between voltage and current.

The impedance of linear loads remains fixed with changing the applied voltage. The fixed

impedance means that the current drawn by the linear load will be sinusoidal as like the voltage

and the current at any time will be proportional to voltage. Linear loads dont produce any new

frequency (harmonics) or change the applied frequency.

Linear loads are made of linear components. Generally resistive loads are referred to as linear

loads. Power factor improvement capacitors, indecent lamps and heaters are the common devices

which are classified as linear loads.

If you increase the voltage from 10V to 20V, current should double. Resistors will do that.

Linear loads generally do not cause any sort of distortion in the power system.

When sinusoidal voltage is applied on a linear load, the result is also sinusoidal which has been

explained earlier. It is shown in the figure below.

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Figure 2.1 (Linear load waveform)

2.2 NON LINEAR LOADS

Non linear Electrical Load is a load where the wave shape of the steady state current does not

follow the wave shape of the applied voltage.

2.2.1 Characteristics of non linear loads 1. Non linear loads change the shape of the current waveform from a sine wave to some other

form.

2. Non linear loads create harmonic currents in addition to the original (fundamental

frequency) AC current causing distortion of the current waveform leading to distortion of

the voltage waveform. Under these conditions, the voltage waveform is no longer

proportional to that of current.

3. Impedance of non linear load changes with the applied voltage. The changing impedance

means that the current drawn by the non linear load will not be sinusoidal even when it is

connected to a sinusoidal voltage. These non-sinusoidal currents contain harmonic currents

that interact with the impedance of the power distribution system to create voltage

distortion that can affect both the distribution system equipment and the loads which are

connected to it.

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2.2.2 Effects of non linear loads on power system The non linear loads will generate harmonics in the electrical distribution network and these

harmonics will create:

1. Large load currents in the neutral wires of a 3 phase system. Theoretically the neutral

current can be up to the sum of all 3 phases therefore causing overheating of the neutral

wire. Since only the phase wires are protected by circuit breakers or fuses, this can result

in a potential fire hazard.

2. Overheating of standard electrical supply transformers which shortens the life of a

transformer and will eventually destroy it. When a transformer fails, the cost of lost

productivity during the emergency repair is much more than the replacement cost of the

transformer itself.

3. Poor power factor conditions that result in monthly utility penalty fees for major users

(factories, manufacturing, and industrial) with a power factor 0.9 and less.

4. Resonance that produces over current surges. In comparison, this is equivalent to

continuous audio feedback through a PA system. This results in destroyed capacitors and

their fuses and damaged surge suppressors which will cause an electrical system shutdown.

5. False tripping of branch circuit breakers.

6. High frequency harmonics can be induced into phone lines and data cabling. The end result

is noisy phone lines and unexplained data lose or data corruption in your LAN or WAN.

7. Heat generation in special facilities such as call centers or data centers due to the large

concentration of monitors and PCs so the air computer room (CRAC) or building air

conditioning system will run longer or harder, therefore requiring more energy to maintain

the desired temperature.

Current pulses are produced instead of a continuous current wave due to harmonics. They are

shown in the figure below.

Figure 2.2 (Non linear load waveform)

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Examples for non linear loads include electronic equipment, electronic/electric-discharge lighting,

adjustable-speed drive systems, and similar equipment.

At this point, a comparison between linear and non linear loads is necessary. Given below is a

table for comparison between linear and non linear loads.

2.2.3 Comparison between linear and non linear loads Linear Loads Non Linear Loads

Ohms Law Ohms law is applicable Ohms law is not applicable

Crest Factor Crest Factor= 1Peak/1 RMS

= 2=1.41

Crest Factor could be 3 to 4

Power Factor Power factor = Watts/ (V X

I) = Cos

Power factor = Watts/ (V X I)

Cos = Displacement

factor X Distortion factor

Harmonics Load current does not contain

harmonics.

Load current contains all

ODD harmonics.

Load Category Could be inductive or

capacitive.

Cant be categorized. As

leading or lagging Loads.

Load Type Resistive, Inductive or

capacitive

Usually an equipment with

Diode and Capacitor.

Neutral Current Zero neutral current if 1 Ph.

Loads are equally balanced

on 3Ph. Mains (Vector sum

of line current)

Neutral current could be 2.7

times the line current even if

1Ph. Loads are equally

balanced on 3 Ph. Mains

Inrush Current May not demand high inrush

currents while starting.

Essentially very high inrush

current (20 time of I Normal)

is drawn while starting for

17pprox.. One cycle.

Table 2.1 (Comparison of linear and non linear loads)

2.3 POWER FACTOR Power factor is the ratio of the real power to the apparent power of a load. It is a dimensionless

unit. It lies in the range of -1 to 1. Real power is the capacity of the circuit for performing work in

a particular time. Its unit is watts. Apparent power is the product of the current and voltage of the

circuit. Its unit is volt amperes.

2.3.1 Causes The cause of positive power factor is that if energy stored in the load is returned to the source, or

due to a non linear load that distorts the wave shape of the current drawn from the source, the

apparent power will be greater than the real power. Whereas, a negative power factor occurs when

the device (which is normally the load) generates power, which then flows back towards the source

(which is normally considered the generator).

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2.3.2 Disadvantages of low power factor The disadvantages of a low power factor are listed below.

1. The electrical machinery e.g. transformers, alternators, switchgears are generally rated in

kVAs. So as the power factor decreases, the rating of machinery will have to be increased

which will make the equipment more expensive.

2. Lower power factor results in a larger conductor size due to larger current.

3. Larger current results in greater 2 losses in all components of the power system. This results in poor efficiency.

4. Low power factor results in poor voltage regulation. This results in unavailability of

voltage at the supply end. Voltage regulators are used in order to keep voltage within

permissible range.

5. Lagging power factor decreases the overall handling capacity of the system.

2.3.3 Power factor for linear loads In a purely resistive AC circuit, voltage and current waveforms are in phase, changing polarity at

the same instant in each cycle. All the power entering the load is consumed. In loads where reactive

loads are present, such as with capacitors or inductors, energy storage in the loads results in a phase

difference between the current and voltage waveforms. During each cycle of the AC voltage, extra

energy, in addition to any energy consumed in the load, is temporarily stored in the load in electric

or magnetic fields, and then returned to the power grid in a fraction of the period later. This

nonproductive power increases the current in the line. Thus, a circuit with a low power factor will

use higher currents to transfer a given quantity of real power than a circuit with a high power

factor. A linear load does not change the shape of the waveform of the current, but may change

the relative phase between voltage and current.

Circuits containing purely resistive elements have a power factor of 1. Circuits containing

inductive or capacitive elements often have a power factor below 1.

AC power has three components:

1. Real power (P)

2. Reactive power (Q)

3. Apparent power (S)

So the power factor is given by:

cos =

Where, is the phase angle between voltage and current. Now consider the following power triangle.

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Figure 2.3 (Power triangle)

From the above figure, it can be observed that:

2 = 2 + 2

2.3.4 Power factor for non linear loads As described earlier, non linear loads generate harmonics. So, the power factor of non linear loads

cannot be calculated in the traditional way like that of linear loads.

The power factor of non linear loads is calculated by taking in account the harmonics generated

by the load. This is done by calculating the distortion power factor.

Distortion power factor is a measure of how much the harmonic distortion of a load current can

decrease the average power transferred to the load. It is given by:

Distortion power factor = 1

1+2 =

1,

Here THD is the total harmonic distortion. 1, is the fundamental component of the current and

is the total current. Both are root mean square-values. Distortion power factor can also be used to describe individual order harmonics, using the corresponding current in place of total

current. This definition with respect to THD assumes that the voltage stays undistorted (sinusoidal,

without harmonics). This simplification is often a good approximation for stiff voltage sources.

THD of typical generators from current distortion in the network is on the order of 12%, which

can have larger scale implications but can be ignored in common practice.

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2.3.5 Power factor correction for linear loads Power factor can be improved by the following methods:

1. Static capacitors can be used to improve the power factor. They are connected in parallel

of the equipment or load whose power factor is to be improved.

2. Synchronous condensers are a good way to improve the power factor. They are basically

synchronous motors running in over excited condition thus acting as capacitors. When it is

connected with the load, it takes the leading current thus improving the power factor.

2.3.6 Power factor correction for non linear loads

Passive PFC

The easiest way to control the harmonic current is to use a filter that passes current only at line

frequency (50 or 60 Hz). The filter consists of capacitors or inductors, and makes a non linear

device act like a linear load.

A disadvantage of passive PFC is that it requires larger value of inductors or capacitors than an

equivalent power active PFC circuit. Also, in practice, passive PFC is often less effective at

improving the power factor.

Active PFC

Active PFC is the use of power electronics to change the waveform of current drawn by a load to

improve the power factor. Some types of the active PFC are boost, buck, buck-boost and

synchronous condenser. Active PFC can be single-stage or multi-stage.

In the case of a switched-mode power supply, a boost converter is inserted between the bridge

rectifier and the main input capacitors. The boost converter tries to maintain a constant DC bus

voltage on its output while drawing a current that is always in phase with and at the same frequency

as the line voltage. Another switched-mode converter inside the power supply produces the desired

output voltage from the DC bus. This approach requires further semiconductor switches and

control electronics, but allows cheaper and smaller passive components. It is frequently used in

practice.

Dynamic PFC

Dynamic power factor correction is also known as real-time power factor correction, is used for

electrical stabilization in cases of rapid load changes (e.g. at large manufacturing sites). DPFC is

useful when standard power factor correction would cause over or under correction. DPFC uses

semiconductor switches, mostly thyristors, to quickly connect and disconnect capacitors or

inductors from the network in order to improve power factor.

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2.4 HARMONICS

As stated previously, non linear loads generate harmonics which can lower the power quality. A

harmonic is a sinusoidal component of a periodic wave or a quantity having a frequency that is an

integer multiple of the fundamental frequency, i.e. if the fundamental frequency is f, the harmonics

have frequencies 2f, 3f, 4f . . . etc. The harmonics have the property that they are all periodic at

the fundamental frequency, therefore the sum of harmonics is also periodic at that frequency. As

multiples of the fundamental frequency, successive harmonics can be found by repeatedly adding

the fundamental frequency. For example, if the fundamental frequency (first harmonic) is 25 Hz,

the frequencies of the next harmonics will be 50 Hz (2nd harmonic), 75 Hz (3rd harmonic), 100 Hz

(4th harmonic) and so on.

Harmonic voltages and currents in an electric power system are a result of non-linear electric loads.

Harmonic frequencies in the power grid are a major cause of power quality problems. Harmonics

in power systems result in increased heating in the equipment and conductors, misfiring in variable

speed drives, and torque disturbance in motors. Reduction of harmonics is considered important.

2.5 DISTORTION FACTOR Distortion factor of a signal is a measurement of the harmonic distortion present and is defined as

the ratio of the sum of the powers of all harmonic components to the power of the fundamental

frequency expressed as a percent of the fundamental. In power systems, lower distortion factor

means reduction in peak currents, heating, emissions, and core loss in motors.

Distortion factor is also known as total harmonic distortion or harmonic factor. It is given by:

THD = 2

2+32+4

2++2

1 x 100

Where is the RMS voltage of nth harmonic and n = 1 is the fundamental frequency.

Nonlinear loads, such as inverters, solid-state rectifiers used in welders, DC power supplies,

variable-frequency drives, and electronic ballasts for lighting are sources of harmonics in the

electrical system feeding these loads. There are specific harmonics associated with each item of

equipment, and equipment manufacturers can usually provide information on the magnitude and

order of harmonics generated by their equipment.

To fully understand what a third harmonic can do to a normal sine wave, consider the following

figure in which a third harmonic adds with a sine wave.

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Figure 2.4 (Third harmonic effect)

2.6 DESIGN RECOMMENDATIONS FOR DISTRIBUTION

SYSTEMS HAVING HARMONICS 1. Use double-size neutral wires or separate neutrals for each phase.

2. Specify a separate full-size insulated ground wire rather than relying on the conduit alone

as a return ground path.

3. On a branch circuit use an isolated ground wire for sensitive electronic and computer

equipment.

4. Isolate sensitive electronic and computer loads on separate branch circuits all the way back

to the electrical panel.

5. Run a separate branch circuit for every 10 Amperes of load.

6. Install a comprehensive exterior copper ground ring and multiple deep driven ground rods

as part of the grounding system to achieve 5 ohms or less resistance to earth ground.

7. Oversize phase wires to minimize voltage drop on branch circuits.

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8. Shorten the distance on branch circuits from the power panel to minimize voltage drop.

9. Oversize all local power sources (generators, UPS) to overcome harmonics effects on them.

2.7 TREATMENT FOR HARMONIC PROBLEMS Harmonic treatment can be performed by two methods:

Filtering.

Cancellation.

1- Filtering

A harmonic 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. Usually this frequency range only accounts for one harmonic frequency. This

application is mostly used when specified for a UPS or variable frequency drive motor in a

manufacturing plant.

2- Cancellation

Harmonic cancellation is performed with harmonic canceling transformers also known as

phase shifting transformers. A harmonic canceling transformer is a relatively new power

quality product for solving harmonic problems in electrical distribution systems. This type of

transformer has built-in electromagnetics technology designed to remove high neutral current

and the most harmful harmonics from the 3rd through 21st. The technique used in these

transformers is known as low zero phase sequencing and phase shifting. These transformers

can be used to treat existing harmonics in buildings or facilities. This same application can be

designed into new devices to prevent future harmonics problems.

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CHAPTER # 3

DESIGN AND WORKING This project is a three phase meter whose purpose is to display the distribution factors which are

power, current, voltage, power factor and the distortion factor.

The following figure will explain the stages of the project.

Figure 3.1 (Main stages)

1. Load is connected to the current and potential transformers.

2. The value of voltage is stepped down in the PT.

3. The CT reduces the value of current to a suitable value which can be measured.

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4. The CTs and PTs are then connected to their circuits.

5. The role of these circuits is to rectify the AC coming from the load.

6. These circuits contain a bridge rectifier and capacitors.

7. The bridge rectifier converts AC into DC.

8. The ripples are then removed by the capacitors.

9. The outputs from the bridge rectifier are also connected to zero crossing detectors.

10. The zero crossing detectors detect the instant at which the current or voltage wave passes

the zero mark.

11. The outputs of CT circuit, PT circuit and zero crossing detectors are connected to the

microcontroller.

12. The microcontroller chosen for this project is PIC18F452.

13. The microcontroller processes the results and sends it to the LCD display.

14. Final results are shown on the LCD display.

The flowcharts and the descriptions for how the results are processed individually are given next.

3.1 CURRENT & VOLTAGE MEASUREMENT

1. As described earlier, the load is connected to CTs and PTs.

2. These CTs and PTs are connected to their respective circuits.

3. The rectified and filtered waveforms of the currents and the voltages are provided by the

circuits to the microcontroller.

4. The microcontroller stores them in the ADC.

5. ADC stands for analogue to digital conversion.

6. As the name implies, the ADC converts the analogue values coming from the circuits into

digital and stores them.

7. These values are then sent to the LCD display.

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Figure 3.2

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3.2 POWER MEASUREMENT

Figure 3.3

1. The procedure to display the power being consumed by the load is almost as similar to

that of voltage and current display.

2. For the display of voltage and current the microcontroller sends their values directly to

the LCD display.

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3. In the case of power, the microcontroller multiplies the values of current and voltage. As,

Power = Voltage x Current

4. This value of power is then sent to LCD display.

3.3 POWER FACTOR MEASUREMENT

Figure 3.4

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1. For the measurement of power factor, output is taken from CT and PT.

2. This output is rectified and then fed to the zero crossing detectors.

3. Zero crossing detectors detect the point at which the current and voltage waves cross the

zero line mark.

4. This output is given to the microcontroller.

5. The microcontroller compares the difference between the zero crossing value of current

and the voltage.

6. The phase difference between the zero crossings of current and voltage is the power factor.

3.4 DISTORTION FACTOR MEASUREMENT

Figure 3.5

Load

PT circuit

Comparison with standard sine function

Calculate amplitude difference

Display result in percentage

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For measuring the distortion factor, multiple techniques can be applied. One such technique is

to compare the distorted wave with an ideal sine wave.

1. As we know that the fundamental frequency of the system is 50 Hz.

2. Harmonics are the multiples of the fundamental frequency which makes the second and

third harmonics as 100Hz and 150Hz respectively.

3. For the calculation of distortion factor, the AC voltage is compared with a standard sine

function.

4. The amplitude of the distorted wave is calculated and it is compared with that of standard

wave.

5. The amplitude difference is calculated.

6. Result is shown in percentage form.

The next figure represents the complete layout of the project. It shows all the transformers and

circuits. It also shows their connections to the microcontroller.

Each phase of the load is connected to the current and the potential transformers. The following

are the inputs being provided to the microcontroller.

3 inputs from CT circuits

3 inputs from PT circuits

3 inputs from CT zero crossing detectors

3 inputs from PT zero crossing detectors

In addition to this, power supply for the microcontroller has been connected.

The microcontroller is providing output to the LCD display which will display the results.

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Figure 3.6 (Complete layout)

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CHAPTER # 4

ELECTRICAL COMPONENTS

4.1 CURRENT TRANSFORMER A current transformer is a device which is used to measure AC current. It reduces the value of AC

current to such a value which is safe for the other components which are connected to it.

A current transformer has primary and secondary windings along with a magnetic core. The current

to be measured flows in the primary winding which produces alternating magnetic field in the

magnetic core. As a result, an alternating current is induced in the secondary winding. This

secondary current is linearly proportional to the primary current.

Figure 4.1 (CT circuit)

In our CT circuit, a bridge rectifier is installed to convert AC into DC. This is done to provide the

output to the microcontroller. The output from the bridge rectifier contains many ripples. To

overcome this problem, capacitors have been introduced after the bridge rectifier. They help in

reducing the ripples.

The current transformer is connected in series with the load.

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Parameter Result (Volts)

Input Voltage 212

Voltage after passing through load 32.1m

Voltage after passing through transformer 3.07

Output Voltage 0.97

Table 4.1 (CT circuit simulation results)

4.2 POTENTIAL TRANSFORMER Potential transformers are also called voltage transformers. In our project, it is being used for

voltage measurement. A potential transformer steps down the AC voltage to a safe level so it can

be measured.

Just like a CT, a potential transformer or simply PT has primary and secondary windings wound

on a metallic core. Primary of this transformer is connected across the phase and ground.PT has

lower turns winding at its secondary. The system voltage is applied across the terminals of primary

winding of that transformer, and then proportionate secondary voltage appears across the

secondary terminals of the PT.

In an ideal PT, when rated burden gets connected across the secondary, the ratio of primary and

secondary voltages of transformer is equal to the turns ratio and furthermore, the two terminal

voltages are in phase opposite to each other. But in actual transformer, there must be an error in

the voltage ratio as well as in the phase angle between primary and secondary voltages.

In our PT circuit, a bridge rectifier is installed to convert AC into DC. This is done to provide the

output to the microcontroller. The output from the bridge rectifier contains many ripples. To

overcome this problem, capacitors have been introduced after the bridge rectifier. They help in

reducing the ripples.

The potential transformer is connected in parallel with the load. The transformer which we have

used as the rating of 240/12 volts.

Figure 4.2 (Potential transformer)

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Figure 4.3 (PT circuit)

Parameter Result (Volts)

Input voltage 212

Voltage after stepping down 11.6

Output Voltage 2.30

Table 4.2 (PT circuit simulation results)

4.3 ZERO CROSSING DETECTOR It is a circuit which is used to detect the time at which the wave crosses the zero mark. It is installed

on all the boards of CTs and PTs.

In our project, zero crossing detector is being used to find the power factor. The zero crossing

detectors installed with the CTs and PTs detect the point at which their waves cross the zero mark.

This data is provided to the microcontroller which calculates the difference between the zero

crossing values of current and voltage waves. As power factor is the phase difference between

current and voltage waves, it is displayed on the LCD display. This is shown in the figure shown

before.

Note that the bridge rectifier used in the zero crossing detector and the CT or PT circuit on which

it will be installed will be common. Unlike shown in the figure, the rectifier will not be provided

220 volts. It is shown here for demonstration only.

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Figure 4.4 (Zero crossing explanation)

Figure 4.5 (Zero crossing detector)

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4.4 B380 (BRIDGE RECTIFIER) This is the rectifier which we have used. In the given circuits diodes have been shown to represent

the rectifier.

Figure 4.6 (B380)

4.5 POWER SUPPLY CIRCUIT The power supply circuit is the circuit which is used to provide power to the microcontroller. It

contains a step down transformer which steps down the AC voltage. The output of the transformer

is connected to a bridge rectifier which converts AC into DC. The output from the rectifier is then

passed through capacitors to filter the ripples. A voltage regulator is installed which further lowers

the voltage and is followed by capacitors.

Figure 4.7 (Power supply circuit)

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4.6 LM7805 (VOLTAGE RGULATOR) This voltage regulator has been used in the power supply circuit. It can provide an output voltage

up to 24V.

Figure 4.8 (LM7805)

4.7 LCD DISPLAY LCD (Liquid Crystal Display) screen is an electronic display module and is used in a wide range

of applications. In this project, we have used 16x2 LDC display. A 16x2 LCD display is a very

basic module and is very commonly used in various devices and circuits. LCDs are economical,

easily programmable, have no limitation of displaying special & can even have custom characters,

animations and so on.

A 16x2 LCD means it can display 16 characters per line and there are 2 such lines. In this LCD

each character is displayed in 5x7 pixel matrix. This LCD has two registers, namely, Command

and Data.

The command register stores the command instructions given to the LCD. A command is an

instruction given to LCD to do a predefined task like initializing it, clearing its screen, setting the

cursor position, controlling display etc. The data register stores the data to be displayed on the

LCD. The data is the ASCII value of the character to be displayed on the LCD.

Pin # Name Function

1 Ground Ground (0V)

2 Supply voltage; 5V (4.7V 5.3V) 3 Contrast adjustment; through a variable resistor 4 Register select Selects command register when low; and data register

when high

5 Read/Write Low to write to the register; High to read from the

register

6 Enable Sends data to data pins when a high to low pulse is given

7 DB0 8 bit data pin








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15 LED +

16 LED -

Table 4.3 (LCD pin configuration)

Figure 4.9 (LCD Display)

4.8 LOAD

1. Three phase load has been made for this project.

2. The load consist of three inductive chokes.

3. Each choke has a rating of 40 watts.

4. In addition to the chokes, a bulb socket has also been installed in series with each of the

choke.

5. Resistive or inductive load can be connected in the load in these sockets.

6. The purpose is to show the change in the distortion level and power factor upon adding a

certain type of load i.e. inductive, resistive or capacitive.

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Figure 4.10 (Load)

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CHAPTER # 5

MICROCONTROLLER

5.1 OVERVIEW

The PIC18F452 belongs to the PIC family of the microcontrollers. This

microcontroller has 40 pins. Its pin configuration is given below.

Figure 5.1 (PIC pin configuration)

The main characteristics of PIC18F452 are given below.

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Parameter Value

Program Memory Type Flash

Program Memory (KB) 32

CPU Speed (MIPS) 10

RAM Bytes 1536

Data EEPROM (bytes) 256

Digital Communication Peripherals 1-UART, 1-A/E/USART, 1-SPI, 1-I2C1-

MSSP(SPI/I2C)

Capture/Compare/PWM Peripherals 2 CCP

Timers 1 x 8-bit, 3 x 16-bit

ADC 8 ch, 10-bit

Temperature Range (C) -40 to 125

Operating Voltage Range (V) 2 to 5.5

Pin Count 40

Table 5.1 (PIC characteristics)

5.2 WORKING OF THE MICROCONTROLLER

The microcontroller plays the most vital role in this project. Its job is to get the data from the

analogue input devices which are current and potential transformers along with the zero crossing

detectors.

An important part of the microcontroller is the analogue to digital converter or ADC. The function

of the ADC is to convert the analogue data coming from the circuits into digital form. There are

ICs available in the market which can perform this task but they will make the circuit more

complex. To avoid their usage, we will use the built in ADC feature of PIC.

The ADC of PIC microcontroller has the following specifications:

1. 10 bit resolution output meaning that an analogue input gets converted into a corresponding

10 bit digital output.

2. 13 channels which means that a total of 13 analogue signals can be converted

simultaneously into digital.

3. Vref+ (RA3) and Vref- (RA2) pins for external reference voltage.

4. 8 selectable clock options.

5. ADC can be in auto triggering mode for continuous A/D conversion.

The following code initializes the ADC with variables and configures the pins.

#define zc_a1 portc.f0



#define zc_v1 portc.f3

#define zc_v2 portd.f0

#define zc_v3 portd.f1

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long volt,amp,watt,pf=0,cont=0,far;

long

volt1=0,volt2=0,volt3=0,amp1=0,amp2=0,amp3=0,watt1=0,watt2=0,wat

t3=0,pf1=0,pf2=0,pf3=0,dis=0;

ADCON1 = 0x80;

TRISA = 0xFF;

TRISb = 0x00;

portb = 0x00;

TRISC = 0X0f;

TRISd = 0X00;

portd = 0x00;

portc = 0x00;

5.2.1 Algorithm for measurement of voltage and current

Figure 5.2 (Voltage & current measurement algo.)

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1. Get the input from potential and current transformers.

2. Set a resolution by: +

1024 1

3. Multiply this value by the input obtained from PT circuit.

4. The same resolution can be applied to calculate the current.

5. For calculating the current, multiply the resolution with the input from the CT circuit.

6. Send the obtained values to the LCD for display.

5.2.2 Algorithm for power measurement

1. The algorithm for power calculation uses the values of current and voltage calculated in

the previous algorithm.

2. The code for power calculation multiplies the values of current and voltage.

3. This result is then sent to the LCD interface.

Figure 5.3 (Power measurement algo.)

The following code is used for the measurement of current, voltage and power:

while (1) {

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//**********************

amp1 = adc_read(0);

amp1 = ( amp1 * 500 ) / 1023;;

//**********************

amp2 = adc_read(1);

amp2 = ( amp2 * 500 ) / 1023;;

//**********************

amp3 = adc_read(2);

amp3 = ( amp3 * 500 ) / 1023;;

//**********************

volt1 = adc_read(3);

volt1 = ( volt1 * 500 ) / 1023;;

//**********************


volt2 = ( volt2 * 500 ) / 1023;;

//**********************


volt3 = ( volt3 * 500 ) / 1023;;

//**********************

watt1 = ( volt1 * amp1 ) / 100;

watt2 = ( volt2 * amp2 ) / 100;

watt3 = ( volt3 * amp3 ) / 100;

//****************************************

5.2.3 Algorithm for power factor measurement

1. For the measurement of power factor, the output from the zero crossing detector comes

into act.

2. When the voltage or current wave crosses the zero mark, the circuit generates a signal.

3. This signal is provided to the ADC.

4. If the wave crosses the zero mark, the ADC will give an output of 1, otherwise zero.

5. The phase difference for the zero crossing values is calculated.

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6. This difference is the power factor.

Figure 5.4 (Power factor measurement algo.)

The code for power factor is given as:

while(!zc_v1);

while(!zc_a1){pf1++;}

pf1=9500-pf1;

pf1=pf1/100;

while(!zc_v1);


pf1=9500-pf1;

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pf1=pf1/100;

//****************************************

while(!zc_v2);


pf2=9500-pf2;

pf2=pf2/100;

while(!zc_v2);


pf2=9500-pf2;

pf2=pf2/100;

//****************************************

while(!zc_v3);


pf3=9500-pf3;

pf3=pf3/100;

while(!zc_v3);


pf3=9500-pf3;

pf3=pf3/100;

5.2.4 Algorithm for measurement of distortion factor

1. For the calculation of the distortion factor, the output from the PT circuit is needed.

2. The AC voltage cannot be directly used as the microcontroller is only capable for 5V.

3. This input is compared with a standard sine function which is provided to the

microcontroller in numerical form.

4. The amplitude difference is calculated between the sine and obtained values is calculated.

5. The result is calculated in percentage.

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Figure 5.5 (Distortion factor measurement algo.)

Following is the standard sine wave function.

unsigned const SINE_WAVE[200] = {

8,8,8,9,9,9,10,11,12,13,14,15,16,18,19,21,23,

25,27,29,31,33,36,38,41,43,46,49,52,54,57,61,64,67,70,74,77,

80,84,87,91,95,98,102,106,109,113,117,120,124,128,132,136,

139,143,147,150,154,158,161,165,169,172,176,179,

182,186,189,192,195,199,202,204,207,210,213,215,218,220,223,

225,227,229,231,233,235,237,238,240,241,242,243,244,245,246,

247,247,247,248,248,248,248,248,247,247,247,246,245,244,243,

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242,241,240,238,237,235,233,231,229,227,225,223,220,218,215,

213,210,207,204,202,199,195,192,189,186,182,179,176,172,169,

165,161,158,154,150,147,143,139,136,132,128,124,120,117,113,

109,106,102,98,95,91,87,84,80,77,74,70,67,64,61,57,54,52,49,

46,43,41,38,36,33,31,29,27,25,23,21,19,18,16,15,14,13,12,11,

10,9,9,9,8,8};

The code for distortion factor measurement is given as:

//****************phase1************************

while(!zc_v1);

for(far=0;far

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//**********************


volt3 = ( volt3 * 500 ) / 1023;;

if(SINE_WAVE[far] == volt3){

dis++;

}}

//************************

dis = dis / 600;

dis = pf1+pf2+pf3;

dis = (dis / 3)-((watt1+watt2+watt3)/150);

5.2.5 LCD initialization

The readings of all the factors will be displayed in LCD display. For this purpose, LCD has to be

initialized. The input ports for the LCD are initialized in this process.

The following code is used for this purpose.

//*******************************

Lcd_Init(&PORTB);

LCD_Cmd(LCD_CURSOR_OFF);

LCD_Cmd(LCD_CLEAR);

LCD_Out(1,1,"Init.....");

delay_ms(2000);

LCD_Cmd(LCD_CLEAR);

The code to display the data is given as:

//***************************data

displ***************************************

LCD_Cmd(LCD_CLEAR);

//********************

Lcd_Out(1,1,"V1=");

lcd_chr_cp(48+((volt1 / 100)%10));

lcd_chr_cp(48+((volt1 / 10)%10));

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lcd_chr_cp(48+((volt1 / 1)%10));

//********************

Lcd_Out(1,9,"A1=");

lcd_chr_cp(48+((amp1 / 100)%10));

lcd_chr_cp('.');

lcd_chr_cp(48+((amp1 / 10)%10));

lcd_chr_cp(48+((amp1 / 1)%10));

//********************

Lcd_Out(2,1,"W1=");

lcd_chr_cp(48+((watt1 / 100)%10));

lcd_chr_cp(48+((watt1 / 10)%10));

lcd_chr_cp(48+((watt1 / 1)%10));

delay_ms(3000);

LCD_Cmd(LCD_CLEAR);

//********************

Lcd_Out(1,1,"V2=");

lcd_chr_cp(48+((volt2 / 100)%10));

lcd_chr_cp(48+((volt2 / 10)%10));

lcd_chr_cp(48+((volt2 / 1)%10));

//********************

Lcd_Out(1,9,"A2=");

lcd_chr_cp(48+((amp2 / 100)%10));

lcd_chr_cp('.');

lcd_chr_cp(48+((amp2 / 10)%10));

lcd_chr_cp(48+((amp2 / 1)%10));

//********************

Lcd_Out(2,1,"W2=");

lcd_chr_cp(48+((watt2 / 100)%10));

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lcd_chr_cp(48+((watt2 / 10)%10));

lcd_chr_cp(48+((watt2 / 1)%10));

delay_ms(3000);

LCD_Cmd(LCD_CLEAR);

//********************

Lcd_Out(1,1,"V3=");

lcd_chr_cp(48+((volt3 / 100)%10));

lcd_chr_cp(48+((volt3 / 10)%10));

lcd_chr_cp(48+((volt3 / 1)%10));

//********************

Lcd_Out(1,9,"A3=");

lcd_chr_cp(48+((amp3 / 100)%10));

lcd_chr_cp('.');

lcd_chr_cp(48+((amp3 / 10)%10));

lcd_chr_cp(48+((amp3 / 1)%10));

//********************

Lcd_Out(2,1,"W3=");

lcd_chr_cp(48+((watt3 / 100)%10));

lcd_chr_cp(48+((watt3 / 10)%10));

lcd_chr_cp(48+((watt3 / 1)%10));

delay_ms(3000);

LCD_Cmd(LCD_CLEAR);

//********************

Lcd_Out(1,1,"PF1=");

lcd_chr_cp(48+((pf1 / 100)%10));

lcd_chr_cp('.');

lcd_chr_cp(48+((pf1 / 10)%10));

lcd_chr_cp(48+((pf1 / 1)%10));

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//********************


lcd_chr_cp(48+((pf2 / 100)%10));

lcd_chr_cp('.');

lcd_chr_cp(48+((pf2 / 10)%10));

lcd_chr_cp(48+((pf2 / 1)%10));

//********************


lcd_chr_cp(48+((pf3 / 100)%10));

lcd_chr_cp('.');

lcd_chr_cp(48+((pf3 / 10)%10));

lcd_chr_cp(48+((pf3 / 1)%10));

//********************

Lcd_Out(2,10,"D=");

lcd_chr_cp(48+((dis / 100)%10));

lcd_chr_cp(48+((dis / 10)%10));

lcd_chr_cp(48+((dis / 1)%10));

lcd_chr_cp('%');

delay_ms(3000);

}}//~!

The figure given shows the connections of the microcontroller to the LCD display.

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Figure 5.6 (LCD and microcontroller interface)

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CHAPTER # 6

CONCLUSION

6.1 RESULTS

After running the project, results were obtained. The following figures show the results for all

three phases.

Figure 6.1 (Phase 1 results)

Figure 6.2 (Phase 2 results)

Figure - 6.3 (Phase 3 results)

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Figure 6.4 (Power factors and distortion factor)

6.2 FUTURE WORK

Power factor and distortion factor are two major problems in the power system. They cause a lot

of disruptions in the power flow and affect the power quality greatly. Hence it is desirable for the

power generating companies and utility companies to overcome these problems.

Many mitigation techniques for improving the power factor are being applied these days to

improve the power factor. They have been discussed previously. In the same way, improving

techniques for distortion factor have also been discussed.

Now a days the power research industry is making efforts in finding more efficient ways to

overcome the noise problem. One such research is being carried out by Lahore electric supply

company (LESCO). They are evaluating the noise levels being generated by the distribution

transformers. The harmonics which are being generated by the distribution transformers are

causing a lot of capital to the company. A similar kind of research is also being funded by

Islamabad electric supply company (IESCO).

Upon the successful determination of noise levels, suitable filters shall be designed.

PLC which stands for power line carrier is a relatively new technique which is being applied now

a days in power distribution. It utilizes communication techniques for power distribution.

Researchers are working on high distortion levels in PLC. So it explains how much harmonics can

affect power distribution.

This meter successfully displays the distribution factors including power and distortion factor.

Most of the industries have installed power factor meters and they are continuously monitoring

their power factor. But if they start to monitor the distortion factor, it can contribute greatly towards

improving the power quality. The same can be applied for domestic and commercial users.

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REFERENCES

http://www.engineering.com/Ask@/qactid/1/qaqid/1916.aspx

http://www.electrical-knowhow.com/2012/03/electrical-load-classification-and_07.html

http://www.visionics.a.se/html/curriculum/Experiments/Zero%20Crossing%20Detector/Z

ero%20Crossing%20Detector1.html

http://www.engineersgarage.com/electronic-components/16x2-lcd-module-datasheet

http://en.wikipedia.org/wiki/Power_factor

http://en.wikipedia.org/wiki/Total_harmonic_distortion

http://www.kmitl.ac.th/~kswichit/PICTHD/picthd.htm

http://microcontrollerslab.com/ac-voltage-measurement-using-microcontroller/

Power factor, harmonic distortion; causes, effects and consideration by Lorenzo Cividino

Power Factor in Electrical Power Systems with Non-Linear Loads by Gonzalo Sandoval

PIC based AC power meter by Rick Bay

Measurement and Simulation of Power Factor using PIC16F877 by Sabir RUSTEMLI,

Muhammet ATES
http://www.engineering.com/Ask@/qactid/1/qaqid/1916.aspxhttp://www.electrical-knowhow.com/2012/03/electrical-load-classification-and_07.htmlhttp://www.visionics.a.se/html/curriculum/Experiments/Zero%20Crossing%20Detector/Zero%20Crossing%20Detector1.htmlhttp://www.visionics.a.se/html/curriculum/Experiments/Zero%20Crossing%20Detector/Zero%20Crossing%20Detector1.htmlhttp://www.engineersgarage.com/electronic-components/16x2-lcd-module-datasheethttp://en.wikipedia.org/wiki/Power_factorhttp://en.wikipedia.org/wiki/Total_harmonic_distortionhttp://www.kmitl.ac.th/~kswichit/PICTHD/picthd.htmhttp://microcontrollerslab.com/ac-voltage-measurement-using-microcontroller/2.2.1 Characteristics of non linear loads2.2.2 Effects of non linear loads on power system2.2.3 Comparison between linear and non linear loads2.3.1 Causes2.3.2 Disadvantages of low power factor2.3.3 Power factor for linear loads2.3.4 Power factor for non linear loads2.3.5 Power factor correction for linear loads2.3.6 Power factor correction for non linear loads2.5 DISTORTION FACTOR2.6 DESIGN RECOMMENDATIONS FOR DISTRIBUTION SYSTEMS HAVING HARMONICS2.7 TREATMENT FOR HARMONIC PROBLEMS3.4 DISTORTION FACTOR MEASUREMENT4.1 CURRENT TRANSFORMER4.2 POTENTIAL TRANSFORMER4.3 ZERO CROSSING DETECTOR4.4 B380 (BRIDGE RECTIFIER)4.5 POWER SUPPLY CIRCUIT4.6 LM7805 (VOLTAGE RGULATOR)4.7 LCD DISPLAY

Real time distribution factor meter for non linear loads

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