murdoch university school of engineering and information ...active and passive filters, distribution...

Thesis Project: Power Quality Analysis at Murdoch University

ENG470: Engineering Honours Thesis

School of Engineering and Information Technology

Murdoch University

Written By: Abdullah Abdullah

Academic Supervisor: Dr. Ali Arefi

Unit Coordinators:

1. Prof. Parisa Bahri

2. Dr. Gareth Lee

A thesis submitted to the School of Engineering and Information Technology,

Murdoch University to fulfil the requirements for the degree of:

H1264: Bachelor of Engineering Honours [BE(Hons)]

1. Electrical Power Engineering

2. Renewable Energy Engineering

Date: 02/07/2018

Author’s Declaration

I, Abdullah Abdullah, do hereby declare that this thesis is an original work and in its entirety

is a product of my own efforts and commitment to the research of power quality analysis at

Murdoch University. This report signifies the final component of the mandatory requirements

for the achievement of a Bachelor’s Degree in Engineering (Honours) majoring in Electrical

Power and Renewable Energy Engineering. To the best of my ability, I have ensured that all

relevant sources which have contributed to the ideas within this thesis be it directly or

indirectly, have been credited and suitably acknowledged.

Name: . . . . . . . . . . . . . . . . . . . . . . . . . .

Date: . . . . . . . . . . . . . . . . . . . . . . . . . . .

Signature: . . . . . . . . . . . . . . . . . . . . . . .

Power Quality Analysis at Murdoch University

iii

Abstract

Introduction of new electronic technologies that are more sensitive to disturbances in the

power network has made it necessary to monitor the quality of power supplied. This project

presents a study of the power quality at Murdoch University, and aims at identifying the

causes of poor power quality and provide the solutions to these power quality problems. The

main objective of this project is to analyse the power quality of the electricity system of

Murdoch University in order to identify the causes of poor power quality and provide

solutions to improve the power quality. Furthermore, for all the specific goals that had been

set before the commencement of this project have all been accomplished. The most common

power quality issues in most electrical networks globally include voltage sags, voltage swells,

voltage transients, and frequency harmonics. Other power quality issues that can be

experienced include voltage flicker, voltage unbalance, inter-harmonics, brownouts, direct

current, short-term and long-term power interruption. A discussion of all these issues has

been conducted in this report with their impacts on equipment in the network identified to

be wear and tear, overheating, tripping of circuit breakers, and improper functioning of

equipment. The compensating devices that can be used for improving power quality such as

Active and Passive filters, Distribution Static Compensator, Dynamic Voltage Restorer, and

Unified Power Quality Conditioner have also been analysed in this report. The direct and

indirect costs of power quality have been reviewed in this project with the finding that 50 %

of the global turnover of the electricity sector equating to 500 billion Euros is lost annually

due to poor power quality. IEEE 519, AS/NZS 61000.3.2.2003, ANSI C84.1, IEEE 1459, EN

50160, and IEC 61000 are some of the power quality standards that have been discussed in


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this project. Based on the data collected from Murdoch University, particularly from 1.330, in

substation 12, South Street Building 330, chancellery. Subsequently, the power quality

problems experienced at the institution include voltage unbalance of 0.295 or 0.3486 % based

on NEMA and IEC formula respectively, a 42.26 % current unbalance, distortions in current

angle, power factor, and harmonic distortion in the range of 1.8 to 2.8 %.


v

Acknowledgements

This report could not have been conceived without the wise guidance and caring support of

those around me. It is here that I would like to express my deepest gratitude for their

unwavering and much needed support throughout the course of my education at Murdoch

University.

First of all, I would like to thank my supervisor Dr. Ali Arefi for his help in this project, through

his constant guidance and by sharing his expertise in Electrical Power Systems. Not only has

it been a pleasure to work with Dr. Ali Arefi, but his experience in Electrical Engineering was

invaluable to me as to improve as an Electrical Power Engineer. Moreover, his outstanding

work ethic, remarkable integrity, and the care he showed to me as his student encouraged

me to do my best in developing this project. It has been an honour Dr. Ali Arefi.

Secondly, I would like to extend my gratitude and love to my family and friends, who have

consistently pushed and supported me throughout my education. This would not have been

possible without them. Furthermore, I would like to thank the Government of Kuwait and

specifically the Ministry of Higher Education for believing in me and for sponsoring me with

this scholarship.

Last but certainly not least, I would like to thank all of the academic staff at Murdoch

University. In particular Prof. Parisa Bahri, Dr. Gareth Lee, Dr. Martina Calais, A/Prof. Graeme

Cole, Dr. David Parlevliet, Dr. Gregory Crebbin, Dr. Jonathan Whale, Dr. Farhad Shahnia, Dr.

Xiangpeng Gao, Dr. Manickam Minakshi, Dr. Linh Vu, and Dr. GM Shafiullah.


vi

Table of Contents

Author’s Declaration ....................................................................................................................

Abstract ..................................................................................................................................... iii

Acknowledgements .................................................................................................................... v

List of Figures ............................................................................................................................. x

List of Tables ............................................................................................................................ xii

List of Abbreviations and Acronyms ....................................................................................... xiii

Chapter 1: Introduction ............................................................................................................. 1

1.1 Background Information about Power Quality ........................................................... 1

1.2 Aims and Objectives .................................................................................................... 3

1.3 Significance of the Project ........................................................................................... 3

1.3.1 Significance to Power Consumers ............................................................................. 3

1.3.2 Significance to the Electric Utility ............................................................................. 4

1.4 Thesis Project Outline ...................................................................................................... 5

Chapter 2: Literature Review ..................................................................................................... 6

2.1 Introduction into Power................................................................................................... 6

2.2 Power Quality Problems ................................................................................................ 10

2.2.1 Voltage Sags ............................................................................................................ 11

2.2.2 Voltage Swells ......................................................................................................... 12


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2.2.3 Voltage Flicker ......................................................................................................... 13

2.2.4 Voltage Unbalance .................................................................................................. 15

2.2.5 Voltage Transients .................................................................................................. 16

2.2.6 Voltage Notching .................................................................................................... 17

2.2.7 Brownouts ............................................................................................................... 19

2.2.8 Short Interruptions of Power .................................................................................. 19

2.2.9 Long Interruptions of Power ................................................................................... 19

2.2.10 Direct Current ....................................................................................................... 20

2.2.11 Electrical Noise ...................................................................................................... 21

2.2.12 Harmonic Distortion.............................................................................................. 21

2.2.13 Interharmonics ...................................................................................................... 23

2.2.14 Electromagnetic Interference (EMI) ..................................................................... 24

2.3 Power Quality Standards ............................................................................................... 25

2.3.1 IEEE 519 Standard ................................................................................................... 25

2.3.2 IEEE 1459 Standard ................................................................................................. 25

2.3.3 ANSI C84.1 Standard ............................................................................................... 25

2.3.4 EN 50160 Standard ................................................................................................. 26

2.3.5 IEC 61000 Standard ................................................................................................. 26

2.3.6 AS/NZS 61000.3.2:2003 Standard ........................................................................... 27

2.4 Power Quality Monitoring ............................................................................................. 28


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2.5 Using Compensating Devices to Improve Power Quality Disturbances ........................ 29

2.5.1 Active and Passive Filters ........................................................................................ 29

2.5.2 Distribution Static Compensator (D-STATCOM) ..................................................... 32

2.5.3 Dynamic Voltage Restorer (DVR) ............................................................................ 33

2.5.4 Unified Power Quality Conditioner (UPQC) ............................................................ 34

2.6 Power Quality Case Studies ........................................................................................... 35

2.7 Costs of Power Quality Problems .................................................................................. 38

Chapter 3: Methodology .......................................................................................................... 40

Chapter 4: Results and Discussion of Data Analysis ................................................................ 42

4.1 Voltage Unbalance ......................................................................................................... 42

4.2 Phase Distortion ............................................................................................................. 46

4.3 Harmonic Distortion ....................................................................................................... 47

4.4 Power Factor .................................................................................................................. 48

Chapter 5: Conclusion and Future Work ................................................................................. 57

5.1 Future Work Opportunities for the Power Quality Analysis at Murdoch University .... 59

Reference List ........................................................................................................................... 61

Appendix .................................................................................................................................. 68

Appendix Part A: EM133 Meter Manual .............................................................................. 68

Appendix Part B: Calculation of Apparent Power and Power Factor .................................. 70

Appendix Part C: Calculation of Voltage Unbalance ............................................................ 71


ix

Appendix Part D: Risk Assessment ....................................................................................... 72


x

List of Figures

Figure 1: Impedance Triangle [36] ............................................................................................. 7

Figure 2: Energy Consumption by Sectors in European Union Countries [12] .......................... 9

Figure 3: Most Common Power Quality Problems [16] ........................................................... 11

Figure 4: Waveform Illustrating Voltage Sags [19] .................................................................. 12

Figure 5: Waveform Showing Voltage Swells [19] ................................................................... 13

Figure 6: Waveform Indicating Voltage Flicker [23] ................................................................ 14

Figure 7: Voltage Unbalance between Three Phases [25] ....................................................... 15

Figure 8: Relationship between Voltage Unbalance and Increase in Temperature [24] ........ 16

Figure 9: Types of Transients [19] ............................................................................................ 17

Figure 10: Voltage Notching [27] ............................................................................................. 18

Figure 11: Direct Current Offset [29] ....................................................................................... 20

Figure 12: Electrical Noise [19] ................................................................................................ 21

Figure 13: Harmonic Distortion [34] ........................................................................................ 23

Figure 14: Passive Low Pass Filter [1] ...................................................................................... 30

Figure 15: High Pass Filter [1] .................................................................................................. 30

Figure 16: Ideal D-STATCOM [20] ............................................................................................ 33

Figure 17: Schematic of a DVR [20].......................................................................................... 33

Figure 18: UPQC Schematic [20] .............................................................................................. 35

Figure 19: System Operation Snapshot [1] .............................................................................. 37

Figure 20: Voltage versus Time for Three Voltage Lines ......................................................... 42

Figure 21: Voltage versus Time Including Average Voltage of the Three Phases ................... 43


xi

Figure 22: Percent Voltage Unbalance for all Three Phases against Time of the Day ............ 44

Figure 23: Current Magnitude versus Time ............................................................................. 45

Figure 24: Percent Current Unbalance for all Three Phases against Time of the Day ............ 45

Figure 25: Voltage Angles for the Three Phases Plotted against Time .................................... 46

Figure 26: Current Angles for Three Phases Plotted against Time .......................................... 47

Figure 27: THD for all the Phases ............................................................................................. 48

Figure 28: Power Factor for all Phases .................................................................................... 49

Figure 29: Real Power for all Phases ........................................................................................ 50

Figure 30: Reactive Power for all Phases ................................................................................. 50

Figure 31: Apparent Power for all Phases ............................................................................... 51

Figure 32: Current Demanded by the Load in each Phase ...................................................... 52

Figure 33: Phase to Phase and Phase to Neutral Voltages at Varying Power Factors............. 53

Figure 34: Unbalance Voltage Factor ....................................................................................... 55

Figure 35: EM133 Meter Manual [65] ..................................................................................... 69


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List of Tables

Table 1: Power Quality Standards ............................................................................................ 27

Table 2: Comparison between Active and Passive filter [43] .................................................. 32

Table 3: Power Data for the Phase A at 12:00:30 am .............................................................. 70

Table 4: Voltage Unbalance Using IEC 61000 Standard........................................................... 71


xiii

List of Abbreviations and Acronyms

A Ampere

a Delay Angle

AC Alternating Current

ANSI American National Standard Institute

AS/NZS Australian/New Zealand Standard

ASDs Adjustable Speed Drives

C Capacitor

DC Direct Current

D-STATCOM Distribution Static Compensator

DVR Dynamic Voltage Restorer

EDC Theoretical Direct Voltage

EMI Electromagnetic Interference

EN European Standard

EPRI Electrical Power Research Institute

EX Direct Voltage Drop

fb Fundamental Frequency of the System

GPO General Purpose Outlet

Hz Hertz

IDC Direct Current in Per Unit on a Converter Base

IEC Electromagnetic Compatibility

IEEE Institute of Electrical and Electronic Engineers


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Is Current Source

IZ Current and Impedance

kHz Kilohertz

kVA Kilo Volt Ampere

kVA Kilovolt-Ampere

kVAr Kilo Volt Ampere Reactive

kW Kilowatt

L Inductor

NEMA National Electrical Manufacturers Association

NPL National Power Laboratory

P Real Power

PCC Point of Common Coupling

PQ Power Quality

PQM Power Quality Monitoring

PV Photovoltaic

Q Reactive Power

R Resistor

RFI Frequency Interference

RMS Root Mean Square

S Apparent Power

THD Total Harmonic Distortion

u Commutation Angle

UBF Unbalance Factor


xv

UPQC Unified Power Quality Conditioner

UPS Uninterruptible Power Supply

V Volt

Vav Average Voltage

Vfrms RMS Voltage of Fundamental Frequency

Vnrms RMS Voltage of the nth Harmonic

Vs Voltage Source

VSC Voltage Source Converter

VSD Variable Speed Drive

VSIs Voltage Source Inverters

Vt Terminal Voltage

Xs System Reactance in Per Unit on a Converter Base

Xt Converter Transformer Reactance in Per Unit on a Converter Base


xvi


1

Chapter 1: Introduction

1.1 Background Information about Power Quality

According to Institute of Electrical and Electronic Engineers (IEEE), power quality is defined as

the idea of powering and grounding electronic equipment in such a way that it is fit for the

functioning of that equipment and well matched with the wiring system of the premises and

other connected equipment [1]. Grounding refers to a conducting connection through which

electrical equipment have a connection to earth [2].

Power quality can also be defined as the ability of a grid or electrical network to supply clean

stable power that is always available when required by a consumer. The cleanliness of the

power is in terms of the wave shape, which should be pure sinusoidal, noise-free, and within

the allowable tolerances for voltage and frequency [3].

The cost and reliability of any electrical system significantly depend on the supplied and

consumed power quality of the system. The demand for clean and reliable power in the world

has increased in the last several decades due to the introduction of new electronic

technologies [4]. There has been tremendous growth in the use of power electronics in almost

every type of electronic device making them more sensitive to the present disturbances in

the network. In most cases, there has not been an improvement in the quality of designs for

electronic devices to accompany its growth [5]. This has resulted in the distortion of the

distribution network. Therefore, the electronic devices may malfunction during operation

under the distorted distribution networks. For this reason, power quality monitoring and

analysis need to be conducted to predict the occurrence of a disturbance, its causes, and to


2

develop a strategy in order to minimize the disturbance with the aim of protecting the devices

connected in the network.

Power quality monitoring (PQM) involves the collection, analysis, and interpretation of raw

power measured data into information that is useful. This process consists of measuring the

currents and voltages of the supply over a specified period and studying their waveforms.

Wiring, grounding, and equipment connections can be inspected throughout power quality

monitoring [6]. PQM is vital to detect potential and present power quality disturbances, which

may damage equipment or decrease their lifespans. Instruments that use monitoring power

quality include:

1) Power quality metre and analyser used for measuring, recording and storing signal

frequency, harmonics, real and apparent power, phase rotation, current, and voltage.

2) Oscilloscope for measuring and displaying harmonics, current, and voltage.

3) Circuit monitor for measuring voltage sag, swell, flicker, and harmonics.

4) Flicker meter for voltage flicker measurement.

5) Disturbance analyser for voltage transients, power outages, and voltage sags

measurement.

6) The in-plant power monitor used for monitoring voltage profile, voltage swells, sags,

flicker, and harmonics in the power system [6].

This project has attempted to perform a power quality analysis at Murdoch University. The

focus of this thesis is to identify the causes of poor power quality at the institution, to quantify

its impacts on equipment and operations and to provide a solution for the improvement of

the quality of power. An extensive study of various literature sources has been conducted to

get background information about power quality, monitoring techniques, disturbances,


3

impacts, and mitigation strategies. Data has then been collected from the university and

analysed to determine the power quality issues affecting Murdoch University, and solutions

are introduced based on the literature reviewed. Afterward, the data is further analysed to

improve the power quality at the institution.

1.2 Aims and Objectives

The major objective of this project is to analyse the power quality of the electricity system of

Murdoch University to identify the causes of poor quality and provide possible solutions in

order to improve the power quality. This can be achieved through the following specific

objectives:

1. To identify power quality issues.

2. To investigate causes, effects, and proper ways of improving poor power quality.

3. To study the IEEE STD 519 standard and others power quality standards.

4. To obtain power data from Murdoch University and using it afterward for quality

analysis against the standards.

5. To calculate the power quality parameters based on collected data.

1.3 Significance of the Project

Monitoring, analysis, and mitigation of (PQ) are factors vital to various sections of the

economy as well as several industries. Subsequently, the significance of this project can be

divided into two main parts: to consumers and the electric utility.

1.3.1 Significance to Power Consumers

Through the collection and analysis of power quality data that has been conducted in this

research, the occurrence of recurrent power quality disturbances can be accurately predicted.


4

This would be significant to consumers as accurate prediction and mitigation of the

disturbances would result in decreased malfunction of electronic devices connected to the

distribution network.

This project is also substantial to consumers, as it would help to decrease the costs associated

with repairs or replacement of malfunctioned electronic devices in the distribution network.

By providing a solution to the power quality disturbances, the likelihood of occurrence of

these disturbances and their impacts would be minimized significantly. Thus, there would be

fewer malfunctioned consumer devices.

The significance of this project to industrial consumers is in the form of experiencing lower

interruptions during production due to power quality issues. The effect of this is increased

production and reduced losses due to equipment damage. Moreover, this reduces the costs

based on idle personnel during interruptions.

1.3.2 Significance to the Electric Utility

Through this study, the primary power quality disturbance in a distribution network has been

identified. The important source of the disturbance either generation, distribution,

transmission, or consumer that can also be determined. These issues make this research

essential to the electric utility operators, as it would help them understand their network

better.


5

1.4 Thesis Project Outline

This dissertation is divided into five chapters which consist of:

Chapter 1 contains the background information on power quality, a brief description

of the research problem and the research focus. Project objectives and significance of

the research are also found in this chapter.

Chapter 2 provides the present literature, the various ideas as well as issues in power

quality analysis. Specifically, it will consider the implementation of compensating

devices to mitigate the effects of power quality disturbances. In addition, the financial

repercussions of power quality problems, along with a multitude of power quality

standards will be examined. Finally, this chapter explores some power quality case

studies.

Chapter 3 describes the methodology of the project. Here the techniques employed in

the research and execution of the project is presented and discussed.

Chapter 4 discusses the data analysis and calculations done to determine the numerous

of power quality problems at the university. Then the results are presented and

reviewed to validate that indeed the power quality problems have been identified

correctly.

Chapter 5 will conclude the project and provide some future work opportunities for

the power quality analysis at Murdoch University.


6

Chapter 2: Literature Review

2.1 Introduction into Power

An electric power system is made up of three main parts: a generation system, which is the

source of power; a delivery system made up of the transmission and distribution networks

and the load that can be transport (traction/railroad), residential, commercial, industrial, and

governmental consumers [7].

Electric power defined as the rate of converting electric energy [8] can be generated using

conventional methods such as hydroelectric power generation, thermal generating plants,

synchronous machinery, and distributed machinery. Moreover, electric power can be

generated using nonconventional methods such as photovoltaic (PV) modules, wind

generation, tidal generation, and advanced technologies like fuel cells [9].

In direct current (DC) systems, power is given as the product of current and voltage [8] thus:

Power (Watts) = Voltage (V) × Current (A) (1)

P = V × I

In alternating current (AC) systems, instantaneous power is given as the product of the

instantaneous current, and instantaneous voltage expressed mathematically as [10]:

p (t) = v(t)i(t) =VmIm

2[cos ϕ + cos(2ωt − ϕ)] (2)

Where: ϕ is the phase angle.

The resistor, inductor, and capacitor define the total impedance of an AC circuit, which affects

the current and voltage waveforms and hence their phase difference. In AC circuits, the

impedance of the circuit is defined as the ratio of the current and voltage phasors created by


7

a circuit component. Both reactance and resistance make up the total impedance (Z) that

restricts the flow of current around the circuit. The following Figure 1 shows an impedance

triangle, which is used to demonstrate the geometric relationship between reactance,

resistance, and impedance [36]

From the impedance triangle, it is clear that the algebraic sum of the reactive and resistive

ohmic values is not equal to the impedance, as a 900 phase difference exists between a pure

reactance and a pure resistance. As a result, the impedance is a vector sum of the reactance

and the resistance and has both of phase angle (𝜃) and of magnitude (Z). When the frequency

of the AC supply changes, the reactance (X) changes but the resistance remains constant, thus

there will be a change in shape of the impedance triangle. The following relationships hold

between resistance, reactance, and impedance [37].

Z2 = R2 + jX2 (3)

cos θ =R

Z (4)

In AC systems, the average power consumed in a circuit is referred to as real power (also

referred to as active power or true power) and is dependent on the power factor (cosine of

the phase angle). The power supplying stored energy in reactive elements is known as the

Figure 1: Impedance Triangle [36]


8

reactive power. As opposed to active power and reactive power, which reduces the power in

the circuit in order to create and reduce both the inductive magnetic fields and capacitive

electrostatic fields thereby decreasing the supply of true power to the load. The power stored

by a capacitors electrostatic field tries to control the voltage while the power stored in the

inductors magnetic field tries to control the current. This result in the generation of reactive

power by capacitors and consumption of the reactive power by inductors. Apparent power is

defined as the product of RMS values of current and voltage across a circuit [10]. These

mathematically are expressed as shown using the following equations 5-7 [11]:

Real Power: P = |V̅||I|̅ cos ϕ (5)

Reactive Power: Q = |V̅||I|̅ sin ϕ (6)

Apparent Power = |S̅| = |V̅||I|̅ = √P2 + Q2 (7)

Power factor defined as the ratio of the active power (P) to the apparent power (S) is an

essential part of an AC circuit [38]. Power factor defines the phase angle between the voltage

and current waveforms and is expressed mathematically as [38]:

Power Factor =P

S=

VI cos θ

VI= cos θ (8)

In a purely resistive circuit, there is zero phase difference between the real and the apparent

power as the voltage and current waveforms are in phase. Accordingly, the power factor will

be unity.

Power Factor = cos(0) = 1 (9)

Unity power factor means that the actual power consumed is equal to the apparent power

consumed. In a purely reactive circuit, the voltage waveform and the current waveform are

90 degrees out of phase. Thus the power factor will be:


9

Power Factor = cos(90) = 0 (10)

This means that the wattage consumed is zero, but there is a voltage and current supplying

the reactive load. Lagging power factor refers to an inductive circuit where the current lags

the voltage while a leading power factor refers to a capacitive circuit where the current leads

the voltage. Improving the power factor by decreasing the reactive power component is

therefore important to have efficient use of the power by the load.

Energy consumption is divided into four major sectors as illustrated in Figure 2 below for

European Union countries. From Figure 2, it is indicated that industry accounts for the highest

consumption of electrical power at 36 % followed by households at 31 %, commercial sectors

at 30 %, and finally transport at 3 % [12].

Figure 2: Energy Consumption by Sectors in European Union Countries [12]


10

2.2 Power Quality Problems

Power quality issues are caused mainly by the use of sensitive electronic loads such as digital

controllers and computers. Some of these devices have problems due to either their proximity

to other electrical equipment or due to disturbances in the powerline since higher power

loads generate greater disturbances. Examples of devices that create high power loads:

electric variable speed drives, welders, and arc furnaces [1].

Impacts of poor power quality include accelerated tear and wear, overheating, improper

function of electrical and electronic equipment, tripping of circuit breakers, and this

sometimes results in hazardous conditions [13].

A survey by experts in power quality show that about half of all power quality problems are

associated with ground current, ground loops, neutral to ground voltages, ground bonds,

grounding, and other ground related issues [14].

Essential power parameters that affect the quality of power delivered include voltage sags,

voltage swells, voltage flicker, voltage unbalance, voltage transients, voltage notching,

brownouts, short-term and long-term power interruptions, direct current, electrical noise,

harmonic distortion, inter-harmonics, and electromagnetic interference. According to

research conducted by EPRI, power quality problems arising from customers premises

account for 70 % of all disturbances, while the network side accounts for 30 % [15]. From

these parameters, the most common power quality problems among American consumers

were identified as voltage sags, voltage swells, voltage transients caused by capacitor

switching, and harmonics among other related issues [16][17]. Figure 3 demonstrates the

most common power quality problems, and this is discussed below.


11

2.2.1 Voltage Sags

Voltage sags, which are also known as voltage dips, define a decrease of the voltage supply

level by 10 -90 % of the normal voltage, over a short duration of time (half a cycle to 1 minute)

[18]. Voltage sags are usually caused by distribution and transmission system faults.

Moreover, faults in installations at the consumer premises, energization of the transformer

and large motors starts, may result in voltage sags [19]. The following Figure 4 represents a

voltage sag.

48%

22%

15%

6%

5%

2%1% 1%

Most Common Power Quality Problems

Voltage sags/swells

Harmonics

Wiring/Grounding

Capacitor Switching

Load Interaction

Other

EMF/EMI

Power Conditioning

Figure 3: Most Common Power Quality Problems [16]


12

Voltage sags can result in crashing of data processing systems or computer systems and the

tripping, or malfunctioning of motors. These may lead to loss of production and idle personnel

that are costly to maintain. A UPS (Uninterruptible Power Supply) can be used to prevent the

crashes, however, it will introduce harmonics into the system [20]. A series active power filter

can be used for compensation of voltage sags from the AC supply and is preferred over the

UPS due to its reduced economic costs and lower component ratings [18].

2.2.2 Voltage Swells

This is referred to as a voltage surge and is an increase of the RMS supply voltage within a

short duration of time. Swells in voltage are usually caused by capacitor switching and faulty

operation of tap changing transformer on the load [21]. Figure 5 shows the voltage swells.

Figure 4: Waveform Illustrating Voltage Sags [19]


13

Short duration voltage swells may result in computer data being erased, loss of production,

and shortening of lives of home appliances, as well as computers due to the stress it puts on

them. Additionally, it can cause tripping of the protective circuits of a Variable Speed Drive

(VSD). Voltage swells lasting for a long duration cause damage to home appliances [20]. To

mitigate this, surge suppressors are typically used to protect sensitive appliances against

transient voltage surges, while power conditioners can be used to shield equipment from

voltage surges [18].

2.2.3 Voltage Flicker

Voltage flicker or voltage fluctuations refer to rapid short-term changes in voltage levels

caused by sudden variations or switching of the load. The voltage levels increase when the

load decreases, and it similarly decreases when the load increases. Based on their frequency

of occurrence, flicker can be divided into four groups; cyclic flicker, cyclic low frequency,

noncyclic frequent, and noncyclic infrequent. Cyclic flicker is the flicker due to periodic

variations in voltage ranging between 10 every second to 2 every second. Cyclic low frequency

Figure 5: Waveform Showing Voltage Swells [19]


14

has voltage variations in the range of 2 every second to 12 every minute. Noncyclic frequent

has voltage variations in the range of 12 every minute to 1 every minute. Noncyclic infrequent

has voltage variations in the range of 1 every minute to 3 every hour [22]. Arc welding

machines, arc furnaces, oscillating loads, reciprocating compressors, pumps, spot welders

both automatic and manual, drop hammers, saws, cranes, hoists, single elevators, and motor

starts are the most common causes of voltage fluctuations [19]. In addition, voltage flicker

decreases the lifespan of electronic equipment, lamps, and adversely affects human health

since it may cause migraines and headaches due to the strain it puts on the eyes. Voltage

stabilizers and motor starters can be used in correction of voltage fluctuations. Figure 6 below

indicates a waveform of voltage flicker.

Figure 6: Waveform Indicating Voltage Flicker [23]


15

2.2.4 Voltage Unbalance

Voltage unbalance discusses the ratio of the negative sequence voltage to the positive

sequence voltage. It can also be defined as a condition where there is a difference between

the phase angle displacement and RMS voltage values of two consecutive phases [19]. This

may occur due to unbalanced phase loads in a distribution system, unbalanced customer

loads, or unbalanced network impedances. Voltage unbalance causes an increase in the

temperature of motors and can result in tripping of large motors. Unless the output DC of the

drive rectifier is filtered properly, AC variable speed drives may also be affected by voltage

unbalance. Voltage regulators are the devices used to correct voltage unbalance [18]. For

utility, voltage unbalance can be mitigated by redistribution of loads or by repairing of

malfunctioning equipment. For adjustable speed drives, DC link reactors and AC line reactors

can be used to decrease the effects of voltage unbalance [24]. The following Figure 7 shows

an example of voltage unbalance in the phase.

Figure 7: Voltage Unbalance between Three Phases [25]


16

Figure 8 below demonstrates the relationship between the increase in temperature and

voltage unbalance. From Figure 8, it can be seen that temperature rises by approximately

twice the square of the percentage of voltage unbalance [24].

2.2.5 Voltage Transients

This refers to a rapid variation in frequency of the voltage in the steady state condition caused

by lightning or switching operations [26]. As a result, voltage transients are classified into

oscillatory and impulsive transients. Oscillatory transients are caused by capacitor switching,

commutation in power devices and resonant circuits which result in a sudden change of

polarity of the voltage lasting between 10 microseconds and 100 microseconds [18]. On the

other hand, impulsive transients are caused by lightning and last between 1 nanosecond and

1 millisecond [19]. These are illustrated in the following Figure 9.

Figure 8: Relationship between Voltage Unbalance and Increase in Temperature [24]


17

Impulsive transients can result in oscillatory transients that may lead to power line insulator

damage as a result of transient overvoltage, caused by the oscillatory transients. Surge

arresters are usually used to suppress the impulsive transients [20].

2.2.6 Voltage Notching

Voltage notching is a repetitive power quality disturbance that occurs during current

commutation from one phase to another during normal working of power electronic devices

such as a rectifier. The difference between notching and harmonics is that notching happens

in steady state. Harmonic analysis starting point is the current waveform, therefore the IZ

drops of harmonic currents can be used for deriving voltage notching. The primary cause of

voltage notching is three phase converters or rectifiers that produce continuous DC. A short

circuit occurs shortly between two phases during the current commutation from one phase

to another [27].

Factors affecting depth of a notch at any point include the point being examined, isolating

inductance between converter/rectifier, and the source inductance. The commutation angle

is the width of the notch determined as [27]:

u = cos−1[cos a − (Xs + Xt)Idc] − a (11)

Figure 9: Types of Transients [19]


18

This can be simplified to the following equation:

cos u = 1 − (2Ex

Edc) (12)

Where:

u: is the commutation angle.

𝑎: is the delay angle.

𝐼𝑑𝑐: is the direct current in p.u on a converter base.

𝑋𝑡: is the converter transformer reactance in p.u on a converter base.

𝑋𝑠: is the system reactance in p.u on a converter base.

𝐸𝑑𝑐: is the theoretical direct voltage.

𝐸𝑥: is the direct voltage drop due to commutating reactance.

Voltage notches introduce high non-harmonic and harmonic frequencies in the radio

frequency range that result in negative effects such as overloading electromagnetic

interference filters and other high frequency sensitive capacitive circuits when it is of

sufficient power and introduction of signal interference into communication and logic circuits.

The remedy for voltage notches involves isolating the critical and sensitive equipment from

the rectifiers. Figure 10 below shows a waveform with notches.

Figure 10: Voltage Notching [27]


19

2.2.7 Brownouts

A brownout is a constant lower voltage condition caused by the loss of supply to one phase

of a distribution transformer with the two remaining phases maintaining their supply. This

results in low voltages between the phase and neutral of about 100 %, 50 %, and 50 % [28].

This can be corrected by using a voltage stabilizer [18].

2.2.8 Short Interruptions of Power

This refers to an event where there is zero voltage. Such a situation occurs for a short time of

approximately 30 seconds or less. These are caused by the automatic opening and closing of

the protective equipment to isolate a faulty area of the network. The leading causes of fault

in a system are insulator flashover, lightning, improper grounding, and insulation failure.

Short interruptions of power may result in data loss, tripping of protection devices, damage

to data processing equipment, and system crashing and lock up [18].

2.2.9 Long Interruptions of Power

This is a condition lasting for more than two cycles where the voltage is zero. It is also referred

to as a blackout and may be caused by utility power failure, fire, power distribution failure,

human error, storms or objects destroying lines and poles and bad coordination or tripping of

a circuit breaker. Long interruptions of power results in the complete shutdown of systems,

data loss, and loss of control of the systems. It may also lead to damage of electrical

appliances [18]. Generators can be used as power backups for this power quality problem.

Nevertheless, it does not protect the equipment against power failure since the failure

actually occurs before the generator is turned on.


20

2.2.10 Direct Current

Equipment at the customer's end that has characteristics of a non-linear load may inject direct

current in the low voltage neutral conductor of the distribution system. Failure of rectifiers

that are commonly used in many AC to DC conversion technologies of modern equipment can

also cause induction of direct current into an AC distribution system. Therefore, this may

result in earthing systems corrosion and the introduction of unwanted current to devices

working at their rated level [28]. Direct current has the effect of causing saturation in the

magnetic circuits of power transformers [18]. Transformer saturation leads to increase of

transformer temperature making the transformer unable to deliver full power to the load and

thus creates instability in electronic load equipment due to waveform distortion. The solution

to direct current is to use modular systems, which are easily replaceable by the user and by

replacing the problem causing equipment that is faulty [29]. Figure 11 below illustrates a

direct current offset.

Figure 11: Direct Current Offset [29]


21

2.2.11 Electrical Noise

This refers to a persistent, oscillatory disturbance of the waveform that has a wide frequency

distribution of up to 200 kHz. Electrical noise is usually induced in the network by

electromagnetic fields and can also be caused by improper grounding [21]. The following

Figure 12 indicates the waveform distortion.

2.2.12 Harmonic Distortion

This refers to a frequent distortion of the sine wave pattern of the supply voltage or current

caused by variable speed drives and solid-state rectifiers that are loads with non-linear

characteristics. Furthermore, the waveform is equal to the total of different sine waves having

various phases and magnitudes and with frequencies, which are multiples of power system

frequency. The causes of harmonics include, non-linear loads (power electronics equipment)

such as data processing equipment, ASDs, switched mode power supplies, high-frequency

lighting, DC brush motors, rectifiers, welding machines, arc furnaces, and electric machines

operating above the magnetic saturation point (knee of the magnetization curve) [30]. The

level of harmonic distortion is usually expressed in terms of Total Harmonic Distortion (THD)

Figure 12: Electrical Noise [19]


22

[31], which refers to the sum of all harmonics of current or voltage waveform divided by the

main component of the current or voltage. This can be expressed mathematically as [32].

THD =√∑ Vnrms

2∞n=2

Vfrms

(13)

Where:

𝑉𝑛𝑟𝑚𝑠: is the RMS voltage of the nth harmonic.

𝑉𝑓𝑟𝑚𝑠: is the RMS voltage of fundamental frequency.

Harmonic distortion may result in transformer heating and increased losses in the copper,

core, and the stray-flux hence may result in erratic tripping of thermal protections and relays.

Furthermore, it may cause cable losses [33], malfunctioning of traffic control or ripple control

systems, increased probability of resonance occurrence, degeneration or failing of power

factor correction capacitors, overload of the neutral conductors in 3 phase systems and loss

of efficiency in electric machines. Finally, it may cause losses in the distribution network due

to harmonic currents, a low power factor, electromagnetic interference (EMI), and

communication system interference [20]. A shunt active power filter can be used to inject an

opposite and equal compensating harmonic current to compensate for harmonic load current

[18]. From Figure 13 below, it can be seen that a base sine waveform, its third harmonic and

the distorted waveform, which is the sum of the base waveform and its third harmonic.


23

2.2.13 Interharmonics

The existence of waveforms of a sinusoidal nature at frequencies that lie between 50 Hz

multiples of the supply frequency is referred to as inter-harmonic interference. These can

appear as a wide band spectrum or discrete frequencies. Spectral components in the quasi-

steady state can be used to define harmonics and inter-harmonics over a range of

frequencies. Mathematically, harmonics, inter-harmonics and sub harmonics can be

described as:

Harmonic: f = 0 ∗ fb where a is an integer > 0 (14)

Interharmonic: f ≠ a ∗ fb (15)

DC: f = a ∗ fb = 0Hz (a = 0) (16)

Sub harmonic: f > 0Hz and f < fb (17)

Where:

𝑓𝑏: is the fundamental frequency of the system.

Figure 13: Harmonic Distortion [34]


24

Sub harmonic is a type of inter harmonic for frequencies less than the fundamental frequency

of the system. Indeed, Interharmonics are mainly caused by cycloconverters that are widely

used in static VAR generators, linear motor drives, and rolling mills. Other causes of inter-

harmonics include low-frequency power line carriers, integral cycle control, induction

furnaces, induction motors, and arcing loads such as arc furnaces and arc welders [35].

These impacts of inter-harmonics include vibrations in induction motors, heating effects

similar to those of harmonics, malfunctioning of ripple control receivers, the flickering of light,

and noise in audio appliances. Interharmonics can cause acoustic noise in power equipment,

malfunctioning of television receivers, and fluorescent lamps [20].

2.2.14 Electromagnetic Interference (EMI)

The interaction between magnetic and electric fields and sensitive electronic devices and

circuits is a high-frequency phenomenon referred to as EMI [2]. The interaction between radio

frequency fields and sensitive communication or data equipment is known as Radio

Frequency Interference (RFI). EMI and RFI result in inductance creation on data carrying

systems. The voltage that is in excess of the operating data levels can create data opposite or

data that is not the same as that travelling in the data line since data line signals are digital

signals in the form of zeros and ones. Therefore, EMI and RFI introduce noise to the system

hence affecting the power quality. The solution to this power quality issue is to employ

shielding of the data devices and their cables or to relocate the data cables and devices from

the EMI/RFI source [29].


25

2.3 Power Quality Standards

Due to the massive costs associated with poor power quality, various standards have been

put in place to give guidelines, recommendations, and limits to assist in ensuring the user

equipment is compatible with the system where it is to be used [39]. These standards include

IEEE 519, IEEE 1459, ANSI C84.1, EN 50160, IEC 61000, and AS/NZS 61000.3.2:2003.

2.3.1 IEEE 519 Standard

IEEE 519 is an international standard drafted by the Institute of Electrical and Electronics

Engineers (IEEE) that gives recommendations to control harmonic distortion levels on the

overall power system. Other IEEE standards on power quality disturbances include IEEE 1100

(Powering and Grounding Sensitive Equipment) and IEEE 1159 (Monitoring and Definition of

Electric Power Quality) [39].

2.3.2 IEEE 1459 Standard

IEEE 1459 is a standard that gives definitions for the measurement of electric quantities under

sinusoidal and non-sinusoidal, single phase and polyphase and balanced and unbalanced

situations. This standard proposes the concepts and the definitions that are essential for

evaluating the quality of transmission of electrical energy. This is for the purposes of designing

measurement instrumentation, for billing, and development of measurement algorithms

[40].

2.3.3 ANSI C84.1 Standard

ANSI refers to American National Standards Institute and gives guidelines on power quality in

the United States based on the IEEE standards and other standards generated by the institute


26

itself. The most common ANSI standard (ANSI C84.1) provides recommendations for steady

state voltage ratings [39].

2.3.4 EN 50160 Standard

The EN 50160 (European Standard) deals with supply quality necessities for European

services. This standard outlines the particular levels of voltage characteristics that must be

adhered to by the utilities and the techniques for assessing compliance. Moreover, the EN

50160 limits itself to voltage characteristics at the PCC (Point of Common Coupling), and

consequently does not stipulate requirements for power quality within the supply, or the

client's facilities. Regarding the limits in EN 50160, it is apparent that these are very similar to

the IEC 61000-3-6 compatibility levels for harmonic voltages with respect to the

corresponding medium and low voltage systems, with the absence of higher order harmonic

limits in EN 50160 being the exclusion [41].

2.3.5 IEC 61000 Standard

The IEC 61000 (Electromagnetic Compatibility (EMC) Standards) categorizes power quality

issues into six categories. Part 1 deals with terminology and definitions and part 2 describes

the environment where the equipment will be used. Part 3 recommends the limits of

disturbances that can be caused by equipment in the power system, while part 4 details the

guidelines and procedures for tests and measurement devices, and tests to confirm

compliance with the standards. Guidelines on how to install equipment that is to be used for

mitigating power quality disturbances are detailed in part 5. Finally, part 6 of the standard

deals with the standards for specific equipment, so that they can be immune to the

disturbance levels of the power system they are to be used in [39].


27

2.3.6 AS/NZS 61000.3.2:2003 Standard

AS/NZS 61000 is an Australian/ New Zealand standard that is compatible with IEEE 519, and

it is similar to IEC 61000. This standard is made up of six parts that prescribe the limits for

harmonics and voltage disturbances produced by equipment whose input current is less than,

equal to or greater than 16 A per phase. It provides the limits for voltage disturbances in

equipment in low voltage systems that are rated less than or equal to 75 A. The standard also

provides the methods to confirm compliance with the set standards [42]. The following Table

1 is a summary of the power quality standards.

Table 1: Power Quality Standards

Power Quality Issue Standard

Harmonics IEEE 519 and AS/NZS 61000 (for Australia

and New Zealand)

Power and grounding IEEE 1100

Monitoring and definition of electric power

quality

IEEE 1159

Measurement of electrical quantities under

different situations

IEEE 1459

Steady state voltage ratings ANSI C84.1 (For America)

Electromagnetic compatibility IEC 61000

Voltage disturbance AS/NZS 61000

Voltage disturbance EN 50160


28

2.4 Power Quality Monitoring

Power quality monitoring (PQM) refers to the process of collection, analysis, and

interpretation of raw measurement data about voltages and currents into useful information

[63]. PQM is done to quantify the power quality phenomena that occur in a specific site on

electric power equipment. It is sometimes conducted to forecast the performance of the load

equipment and to choose power quality attenuating systems. In some cases, PQM is

performed to identify the incompatibilities between the consumer loads and the supply. In

other case, it is done to test the electrical environment at a specific site for the equipment

and machinery required [64].

Appropriate monitoring equipment is required to perform power quality monitoring. The

input and output interface of the power quality monitoring equipment include; input

channels, analogue inputs/outputs, digital inputs and outputs and communication and

networks. Power quality monitoring equipment have the following functions [4]:

Capture of data by present thresholds. The capture of measured parameters is

conducted when a disturbance repeats at set time intervals or goes beyond a present

threshold (event logging) with the time intervals and thresholds being set up by the

user.

Capture of data by self-adjusting thresholds. A steady-state norm is used to set the

thresholds by a monitor.

Capture of data that is triggered externally. This is a feature provided by most

monitors.

Manual data capture. A manual trigger function is provided by the most monitor,

which is for a snapshot of the present situation.


29

Time interval recording and data logging. Continuous monitoring of parameters is

done using data logging with capture achieved at user established time intervals.

Waveform capture. Certain monitors can capture waveforms for voltage and current.

They can then be downloaded to a PC or can be viewed by built-in displays.

Time synchronization. A radio signal, GPS or an external time signal can use for time

synchronization by some power quality monitors.

Firmware. New releases of firmware by some monitor manufacturing companies are

done periodically. This new firmware is used to improve the existing set of the meter

and for correcting errors in metering algorithm without the need for buying new

hardware.

2.5 Using Compensating Devices to Improve Power Quality Disturbances

2.5.1 Active and Passive Filters

An active filter is an electronic filter device that uses active components such as transistors or

operational amplifiers, both of which require an external power source. However, a passive

filter does not require an external power source, and it is made from passive elements mostly

linear elements such as transformers, inductors, capacitors, and resistors or nonlinear

elements or complex linear elements such as transmission lines [43].

A passive filter is a device that is made up of passive elements and therefore requires an

external power source for its operation. Passive filters are mainly used for frequencies in the

range 100-500 kHz [44]. Filters can be classified into five types based on the transfer function

coefficients. These are low pass, high pass, band pass, notch, and all pass [44].

Low pass filter transfer function is [1]:


30

TFLP(s) =a0

s2 + b1s+b0=

KωP2

s2 + (ωP

QP) s + ωP

2 (18)

Figure 14 below represents the different low pass filter designs and characteristics.

High pass filter transfer function is [1]:

TFHP(s) =a2s2

s2 + b1s + b0=

Ks2

s2 + (ωP

QP) s + ωP

2 (19)

Figure 15 below indicates the high pass filter design and characteristics.

Figure 14: Passive Low Pass Filter [1]

Figure 15: High Pass Filter [1]


31

Band pass filter transfer function is [1]:

TFBP(s) =a1s

s2 + b1s+b0=

K (ωP

QP) s

s2 + (ωP

QP) s + ωP

s (20)

Notch filter transfer function is [1]:

TFN(s) =a2s2 + a0

s2 + b1s + b0=

K(s2 + ωz2)

s2 + (ωP

QP) s + ωP

2 (21)

All pass filter transfer function is [1]:

TFAP(s) =a2s2 + a1s + a0

s2 + b1s + b0=

K [s2 − (ωP

QP) s + ωP

2]

s2 + (ωP

QP) s + ωP

2 (22)

Active filters can be high pass, low pass, band pass, and notch filters. Passive filters can be

only high pass, low pass, and bandpass filters. Active and Passive filters are used in

attenuation of frequencies that are not within their cut off points. Consequently, find

applications in the load compensating devices, telephone systems for decoding of dual tone,

instrumentation, and in data acquisition systems [43]. Table 2 below summarizes the

comparison between active and passive filter.


32

Table 2: Comparison between Active and Passive filter [43]

Active Filter Passive Filter

Requires an external power source Requires no external power source

Made of active components Made of passive components R, L, and C

Has high input and low output impedance Has low input and high output impedance

Has power gain in output signal Has no signal gain

Has oscillations and noise due to feedback

loops for regulating active components

Has low noise due to thermal noise in

elements

Does not consume energy of signal Consumes energy of signal

Does not use inductors Uses inductors

Has stable tuning, accuracy, and high

immunity to EMI

Has self-regulation of voltages driving loads

and has no bandwidth restrictions, thus

operates at higher frequencies

2.5.2 Distribution Static Compensator (D-STATCOM)

Low power factor, harmonic distortion, voltage swells, and voltage sags can be enhanced

using current injected by a Distribution Static Compensator (D-STATCOM) [45]. The D-

STATCOM is a device that is used to limit the reactive power flow in a distribution system

through compensation and can be based on a voltage source converter (VSC) [46]. A VSC is

capable of generating a sinusoidal voltage of any desired phase angle, frequency, and

magnitude. The VSC relies on energy storage devices such as capacitors that supply it with a

DC Voltage that is then used to switch the solid-state electronics inside the VSC. Then it injects

the voltage difference or completely replaces the voltage. The voltage difference refers to the

difference between the actual voltage and the nominal voltage [46]. The following Figure 16

demonstrates a distribution system compensated by an ideal D-STATCOM connected in a

shunt configuration.


33

From Figure 16, the D-STATCOM is functioning in current control mode and hence is

represented by a current source Is.

2.5.3 Dynamic Voltage Restorer (DVR)

Sensitive loads can be protected from voltage sags, surges, or disturbances using a dynamic

voltage restorer (DVR). A voltage source injecting a voltage Vf can be used to represent an

ideal DVR for protection of sensitive loads as illustrated in Figure 17.

Figure 16: Ideal D-STATCOM [20]

Figure 17: Schematic of a DVR [20]


34

This device can be constructed so that it is able, or not able to supply or absorb real power.

Voltage control of the DVR is done by regulation of the bus voltage to any value by measuring

the terminal voltage Vt. Then the balance is supplied through of for a DVR which is designed

to be able to absorb or supply real power. If the DVR is not able to absorb or supply any real

power during steady state, it will perform this throughout transients [20].

2.5.4 Unified Power Quality Conditioner (UPQC)

A UPQC uses a common capacitor for DC energy storage when connected to two voltage

source inverters (VSIs). One of the VSIs is connected in shunt with the AC line whereas the

other is connected in series with this same AC line. A UPQC is used to compensate for

harmonics, reactive power, negative sequence current, voltage imbalance, and voltage flicker

[47]. Voltage imbalance and voltage flicker are eliminated from the load terminal voltage by

the series VSI that injects a series voltage at the point of common coupling. A series voltage

proportional to the line current can be injected into the distribution line to attenuate current

harmonics [20]. The shunt VSI is employed in this device to provide a path for the real power

to flow to help in the functioning of the VSI connected in series [20]. It can be seen from Figure

18, which represents a UPQC in right shunt compensation configuration.


35

2.6 Power Quality Case Studies

Power Quality monitoring research has been a topic that has attracted considerable interest

in recent times. Some of the consequential research includes: a study in Buffalo New York

sponsored by Niagara Mohawk Power Corporation in mid- 1989. This study showed that most

power quality problems originate from the end user’s equipment [48]. Moreover, a five-year

study of single phase electrical disturbances in normal mode in 1990 by the National Power

Laboratory (NPL), indicated the effects of capacitor switching which was observed in most

locations under study with the magnitude of maximum voltage not being so severe at these

sites [49].

A survey by Electrotek Concepts Inc. who were contracted by the Electrical Power Research

Institute (EPRI) in 1990 showed harmonic distortions, transients, voltage sags, and short

power interruptions as the most common type of power disturbances [50].

Other case studies include the Wisconsin Public Power Inc. [51] that installed power quality

meters at the input of equipment to identify the cause of circuits tripping. This was later found

to be capacitor banks. Filters and chokes were then added at these inputs to solve the

Figure 18: UPQC Schematic [20]


36

problem. The same company installed meters to identify the cause of flickering light and

computer problems for an industrial consumer. This was identified to be the several large

single-phase welders in the company. This issue was solved by installing a more massive

transformer with larger conductors at the industrial company. A recommendation was also

provided to the company to add a second service line for the welders [51].

Power quality research was performed for a manufacturing plant [52] that had experienced a

failure of a recently bought test instrument when it was plugged into a GPO (General Purpose

Outlet). The problem was discovered to be the rated RMS voltage of 245 V of the test

instrument that was lower than the Australian Standards RMS voltage of 253 V. This was

solved by using a constant voltage transformer between the test equipment and the GPO that

would both suppress the voltage spikes and lower the RMS voltage.

Another case study conducted on a commercial office building involved utilizing two banks of

AC motors with variable speed drives (VSDs) for control of heating, ventilation and air

conditioning [1]. A 45 kVA transformer was used in order to service each of the banks. The

following Figure 19 indicates the snapshot of the system operation.


37

From Figure 19, it can be seen that after reaching peak voltage, the variable speed drives

demand peak current with the neutral current shown in the second figure made up of 180 Hz

current that peaks above 150 Amperes. The neutral current is a 3rd harmonic that is a common

occurrence when there is a concentration of single- phase electronic loads. For this site,

heating of the service transformer was the main problem due to the third harmonic. The

transformer was not correctly sized for the load, therefore, calculations were done based on

IEEE 519 harmonics guidelines, and it was found that there was at least 5 kVA load on the

transformer above its nominal de -rated capacity. For this site, neutral current limiting devices

or phase shifting transformers were not required because of the low neutral to the ground

voltage and the isolated nature of the VSDs. New rated transformers for every bank was the

solution to the power quality problem for this site [1].

Figure 19: System Operation Snapshot [1]


38

2.7 Costs of Power Quality Problems

Quantifying the cost of power quality problems is not an easy task as there are both direct

and indirect costs. Direct costs are directly related to disturbances and include production

loss costs, damage to equipment expenses, environmental or financial penalties, restart of

process costs, salary expenditures during downtimes, and resources and downtime that is not

recoverable. In addition, it describes the human health and safety direct costs, loss of quality

of semi-finished products, financial penalties due to breached contracts, and utility costs due

to power interruptions. Organizations incur indirect costs, and it includes the cost of restoring

a brand, loss of market share and postponement of income or revenue of an organization

[53].

Various studies have been conducted to provide the quantitative economic costs of poor

power quality. The cost was estimated at a few tens of billions of dollars in early 1990s, and

this had grown to a few hundreds of billions of dollars by 2003 [4]. It is estimated that globally,

500 billion euros amounting to 50 % of the electricity sector global turnover is lost annually

because of poor power quality [54]. Another study [55] indicates that the US economy loses

between 104 billion dollars and 164 billion dollars per year due to outages alone. Moreover,

6.7 billion dollars are lost by industrial economies and the digital economy in the US due to

disturbances excluding voltage sags with a further 15 billion to 24 billion dollars lost to other

power quality problems. An estimated 100 billion euros is lost annually in the world due to

harmonics according to a Eurelectric report [56]. Another study also showed that different

industries experience different costs due to poor power quality. For instance, a

telecommunications company losses up to 30 000 euros every minute due to power outages,


39

while as high as 3.8 million euros is lost by a semiconductor facility due to one power quality

disturbance [57].


40

Chapter 3: Methodology

The approach used in this project involved using of actual current and voltage data in the

analysis of power quality issues experienced at Murdoch University. The current and voltage

data was measured using an EM133 meter installed at 1.330, in substation 12, South Street

Building 330, chancellery.

Data measured from the electrical systems at Murdoch University, especially from 1.330

South Street Building 330, Chancellery, and Substation T12, and it was saved in the form of

spreadsheets in order to perform the analysis. Then the data was extracted from these

spreadsheets and were used to plot graphs for all the measured variables in order to obtain

a visual impression of the data. Calculations were performed where applicable (voltage and

current unbalance) and graphs for the calculated variables were plotted to show the trend

existing in the electrical network.

There are two significant methods were used in the calculation of voltage unbalance. The first

method involves calculation of the negative phase sequence voltage and positive phase

sequence voltage from the phase voltage phasors. The voltage unbalance is then the ratio of

the negative phase sequence to the positive phase sequence multiplied by one hundred. This

method is based on IEC 61000 standards. The second method that is related to National

Electrical Manufacturers Association (NEMA) is determined by finding the maximum

deviation from the average line voltage and multiplying this deviation by one hundred.

Afterward, the graphs were compared to the theoretical charts for each power quality issue

to identify the PQ issues existing at the institution. After identification of the power quality

issues, its effects on the other parameters such as temperature, phase, current, voltage, or


41

power were investigated. This was conducted by plotting graphs of these measured

parameters throughout the occurrence of the power quality problem then the trend

analysed. In other cases such as in voltage disturbance, calculations were done to indicate its

effect on the temperature rise due to loading. Finally, the results of this analysis were

compared with theoretical knowledge from journal publications and literature focusing on

power quality problems.

In order to test the power quality devices, there are three imperative objectives that have

been taken into account include:

1) To determine the types and magnitude of power quality disturbances, which

produced by a device connected to the power system.

2) To test power quality mitigation devices for their ability in order to reduce

disturbances.

3) To test electrical devices for their performance in terms of disturbances of power

quality.


42

Chapter 4: Results and Discussion of Data Analysis

4.1 Voltage Unbalance

The following Figure 20 illustrates the voltages of three-phase to neutral lines. From Figure

20, it can be seen that the magnitude of voltage A-N is lower than the magnitudes of voltage

B-N and C-N. Further investigation and calculations were therefore carried out to prove the

level of voltage unbalance.

The average voltage magnitude at the various times is given as

Vav =VL1 + VL2 + VL3

3 (23)

Plotting this average value together with the three voltages gives the graph in Figure 21

below.

234

235

236

237

238

239

240

241

242

243

12:00:00 AM 2:24:00 AM 4:48:00 AM 7:12:00 AM 9:36:00 AM 12:00:00 PM 2:24:00 PM

Vo

ltag

e (

V)

Time of the Day

Voltage Magnitude versus Time

Voltage A-N Magnitude Voltage B-N Magnitude Voltage C-N Magnitude

Figure 20: Voltage versus Time for Three Voltage Lines


43

The difference between each phase voltage and the average voltage was determined for all

times given. The largest unbalance was determined to be 0.7 V in line voltage A-N. The

percent voltage unbalance consequently is [58]:

% Voltage Unbalance =0.7

236.9∗ 100 = 0.295 % (24)

Figure 22 below shows the percent voltage unbalance for each phase plotted against time.

234

235

236

237

238

239

240

241

242

243

12:00:00 AM 2:24:00 AM 4:48:00 AM 7:12:00 AM 9:36:00 AM 12:00:00 PM 2:24:00 PM

Vo

ltag

e (

V)

Time of the Day

Voltage Magnitude versus Time for a Three Phase System

Voltage A-N Magnitude Voltage B-N Magnitude

Voltage C-N Magnitude Average Voltage magnitude

Figure 21: Voltage versus Time Including Average Voltage of the Three Phases


44

Since the percent voltage unbalance is less than 2 %, the voltage can be used safely with

three-phase equipment [58]. The temperature rise due to this voltage unbalance would also

be low as indicated in equation 25 below.

% Temperature Rise = 2 ∗ (% Voltage Unbalance)2 (25)

= 2 ∗ (0.295)2 = 0.174 Degree Celsius

By plotting the line current magnitudes with time, Figure 23 was obtained. From Figure 23,

the current unbalance can be determined using an equation similar to equation 24. The

largest unbalance was determined as 11.2233 Amps in line current A.

% Current Unbalance =11.2233

26.5567∗ 100 = 42.26 % (26)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

12:00:00 AM 2:24:00 AM 4:48:00 AM 7:12:00 AM 9:36:00 AM 12:00:00 PM 2:24:00 PM

% V

olt

age

Un

bal

ance

Time of the day

Percent Voltage Unbalance

%Unbalance A %Unbalance B % Unbalance C

Figure 22: Percent Voltage Unbalance for all Three Phases against Time of the Day


45

The percent current unbalance for each phase was plotted against time of the day as

illustrated in Figure 24 below.

0

50

100

150

200

250

12:00:00 AM 2:24:00 AM 4:48:00 AM 7:12:00 AM 9:36:00 AM 12:00:00 PM 2:24:00 PM

Cu

rre

nt

Mag

nit

ud

e (

A)

Time of the Day

Current Magnitude versus Time

Current A Magnitude Current B Magnitude Current C Magnitude

Figure 23: Current Magnitude versus Time

0

5

10

15

20

25

30

35

40

45

12:00:00 AM 2:24:00 AM 4:48:00 AM 7:12:00 AM 9:36:00 AM 12:00:00 PM 2:24:00 PM

% C

urr

en

t U

nb

alan

ce

Time of the Day

Percent Current Unbalance

% Unbalance current A % Unbalance Current B % Unbalance Current C

Figure 24: Percent Current Unbalance for all Three Phases against Time of the Day


46

The current unbalance of 42.26 % is very high and unacceptable. This may cause heating in

the load such as in the motor or transformer winding that degrades the load. Besides, due to

this unbalance I2R, losses in the cables increase, and this may lead to lower efficiency of the

load.

4.2 Phase Distortion

As it can be seen from Figure 25, for voltage angle shows that there is no phase distortion

during the duration of the measurement. All phases remain 120 electrical degrees apart

during the entire measurement period. As a result, phase distortion is not a power quality

issue experienced at Murdoch University.

On the other hand, Figure 26 demonstrates the current angle for the different line currents.

From Figure 26, it can be seen that all three phases have distortions in the current angle. The

phase angle for Current A fluctuates between -10.2 to -41.8 electrical degrees, the angle for

-150

-100

-50

0

50

100

150

12:00:00 AM 2:24:00 AM 4:48:00 AM 7:12:00 AM 9:36:00 AM 12:00:00 PM 2:24:00 PM

Vo

ltag

e A

ngl

e

Time of the Day

Voltage Angle versus Time

Voltage A-N Angle Voltage B-N Angle Voltage C-N Angle

Figure 25: Voltage Angles for the Three Phases Plotted against Time


47

current B fluctuates between -97.8 to -157 electrical degrees, and the phase angle for current

C fluctuates between 79.6 to 141.7 electrical degrees. This variation in current angles can be

due to the varying reactance of the load, or it may be due to the unbalanced degradation in

the windings of the three-phase loads in the system.

4.3 Harmonic Distortion

Figure 27 demonstrates the variation of the Total Harmonic Distortion (THD) of each phase

voltage with time.

-200

-150

-100

-50

0

50

100

150

200

12:00:00 AM 2:24:00 AM 4:48:00 AM 7:12:00 AM 9:36:00 AM 12:00:00 PM 2:24:00 PM

Cu

rre

nt

An

gle

Time of the Day

Current Angle versus Time

Current A Angle Current B Angle Current C Angle

Figure 26: Current Angles for Three Phases Plotted against Time


48

From Figure 27, it is clear that all the three phases have a THD that lies between 1.8 to 2.8 %.

According to IEEE STD 519 and AS/NZS 61000 standards, the recommended value of THD

should not exceed 5 % for the operation of computers and other associated equipment such

as programmable controllers [59][42].

4.4 Power Factor

The power factor affects the reactive power, the real and the apparent power in an electrical

system. An increase in power factor results in a decrease in the reactive and apparent power,

but an increase in the real power [2]. This is showed in Figures 28, 29, 30, and 31 generated

from experimental data.

0.00

0.50

1.00

1.50

2.00

2.50

3.00

12:00:00 AM 2:24:00 AM 4:48:00 AM 7:12:00 AM 9:36:00 AM 12:00:00 PM 2:24:00 PM 4:48:00 PM

Tota

l Har

mo

nic

Dis

tort

ion

Time of the Day

Total Harmonic Distortion

THD Voltage V1 (%) THD Voltage V2 (%) THD Voltage V3 (%)

Figure 27: THD for all the Phases


49

From Figure 28, it can be seen that the power factor for the neutral line is 1 while that for

phases B and C is -1 between 12:00:00 am and 1:00:30 am. At this time, the power factor for

phase A lies between 0.5 and 1. Indeed, a negative power factor means that power is

returning to the source. Between 1:00:30 am and around 3:00:30 am, the power factor for

phase B, C, and the neutral line is 1. This means the load supplied by these phases was purely

resistive (there were no inductive loads connected to these phases).

Throughout these times, the real and apparent powers are very low while the reactive power

is zero as can be seen from figures 29, 30, and 31. Between 5:00:00 am to 1:41:00 pm the

real, reactive, and apparent powers increase, which results in a power factor decrease during

this time. This proves the argument that an increase in the power factor results in a reduction

of the reactive power. It is worth noting that the real power at all times is always higher than

the reactive power during the time of measurement.

-1.50

-1.00

-0.50

0.00

0.50

1.00

1.50


Po

we

r Fa

cto

r

Time of the Day

Power Factor

Power Factor A (%) Power Factor B (%) Power Factor C (%) Power Factor (%)

Figure 28: Power Factor for all Phases


50

0.00

20.00

40.00

60.00

80.00

100.00

120.00


Re

al P

ow

er

(kW

)

Time of the Day

Real Power

Real Power A (kW) Real Power B (kW) Real Power C (kW) Real Power (kW)

Figure 30: Reactive Power for all Phases

-10.00

0.00

10.00

20.00

30.00

40.00

50.00

60.00

70.00

80.00


Re

acti

ve P

ow

er

(kV

Ar)

Time of the Day

Reactive Power

Reactive Power A (kVAr) Reactive Power B (kVAr)

Reactive Power C (KVAr) Reactive Power (kVAr)

Figure 29: Real Power for all Phases


51

The effect of a low power factor is an increase in current demanded by the load. By comparing

Figures 32 and Figure 28, it is clear that phase A has the lowest power factor and the highest

current demanded by the load followed by phase C and finally phase B.

0.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00


Ap

par

en

t P

ow

er

(kV

A)

Time of the Day

Apparent Power

Apparent Power A (KVA) Apparent Power B (kVA)

Apparent Power C (kVA) Apparent Power (kVA)

Figure 31: Apparent Power for all Phases


52

Figure 32: Current Demanded by the Load in each Phase

As a result, the power factor has the effect of increasing the voltage drop in transmission and

distribution lines because of the increase in current demanded by the load. This is evidenced

by Figure 33 below, where the phase-to-phase voltages, as well as the phase to neutral

voltages, decrease as the power factor decreases for all the three phases.

0.00

20.00

40.00

60.00

80.00

100.00

120.00

140.00

160.00

180.00

200.00

12:00:00 AM 12:00:00 AM 12:00:00 AM 12:00:00 AM 12:00:00 AM 12:00:00 AM 12:00:00 AM

De

man

d C

urr

en

t (A

)

Time of the Day

Demand Current of the Load

Demand Current A (A) Demand Current B (A) Demand Current C (A)


53

According to IEC 61000 standard, voltage unbalance is calculated as [60]:

UBF =V−

V+∗ 100 (27)

Where:

𝑉−: is the negative phase sequence voltage.

𝑉+: is the positive phase sequence voltage.

The negative phase sequence and positive phase sequence voltage are calculated from the

phase voltage phasors using the following equation [60]:

V− =1

3(Vr + a2Vy + aVb) (28)

V+ =1

3(Vr + aVy + a2Vb) (29)

While the zero sequence, voltage is calculated as [60]:

0.00

50.00

100.00

150.00

200.00

250.00

300.00

350.00

400.00

450.00


Vo

ltag

es

(V)

Time of the Day

Phase to Phase and Phase to Neutral Voltages

Voltage A-B (V) Voltage A-N (V) Voltage B-C (V)

Voltage B-N (V) Voltage C-A (V) Voltage C-N (V)

Figure 33: Phase to Phase and Phase to Neutral Voltages at Varying Power Factors


54

V0 =1

3(Vr + Vy + Vb) (30)

Where:

a = 1∠1200

Vr: is the red phase.

Vy: is the yellow phase.

Vb: is the blue phase.

The voltage unbalance factor can also be calculated using the equation below [60]:

UBF = √1 − √3 − 6β

1 + √3 − 6β∗ 100 (31)

Where:

β =|Vry|4 + |Vyb|4 + |Vbr|4

(|Vry|2 + |Vyb|2 + |Vbr|2)2 (32)

The IEC 61000 voltage unbalance factor was calculated, and refer to Appendix Part C for more

information. This was repeated for all the values of voltages collected every half second

between 12:00:30 am up to 1:45:30 pm. Due to the huge amount of data, excel spreadsheet

was used in order to compute the voltage unbalance and to plot the voltage unbalance

variation with time. A large amount of data from the spreadsheet could also not be included

in this section.


55

From the data given, the voltage unbalance experienced by the system during the duration of

the test is indicated in Figure 34 below.

From Figure 34, it can be seen that the largest voltage unbalance is 0.3486 %, which is

experienced at 12:41:00 pm. In fact, voltage unbalance at this time may be due to higher load

on one phase compared to the load on the other phases. For example, if most people use the

library and labs at this time of the day and both of these facilities are on one phase say the

yellow phase, then it means the load on the red and blue phases would be less thus there

would be a voltage unbalance. It all depends on the trend in the institution, and probably at

this time also the cafeteria is at full capacity meaning more power consumed at this time of

the day. At night or early in the morning, the voltage unbalanced may be lower because it is

not the peak time of power consumption. Not all facilities are working at optimal condition,

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4


% U

nb

alan

ce V

olt

age

Fac

tor

Time of the Day

UBF

UBF(sqrt((1-a)/(1+a))*100)

Figure 34: Unbalance Voltage Factor


56

therefore, there may a voltage unbalance. Nevertheless, it definitely must be lower than

when facilities at working at the almost optimal condition.

In comparison, voltage unbalance according to National Electrical Manufacturers Association

(NEMA) is defined as the maximum deviation from the average line voltage referred to the

average of the line voltages times 100 [61]. Mathematically, this is given as [62], and it was

calculated using equation (24):

Vav − VL

Vav∗ 100 (33)

Where:

Vav =VL1 + VL2 + VL3

3 (34)


57

Chapter 5: Conclusion and Future Work

To summarize, this project has discussed and analysed about power quality analysis at

Murdoch University, in particular from 1.330, in substation 12, South Street Building 330,

chancellery. From the literature in this project, the most common type of power disturbances

was identified to be harmonic distortion, voltage transients, voltage sags, and short power

interruptions. In addition, from the literature, it was found that most of the power quality

problems originate from the end user’s equipment.

Costs that are associated with poor power quality are classified into direct costs and indirect

costs. Direct costs include production losses, costs associated with damage to equipment,

environmental and financial penalties, costs based on restarting the process, expenditure on

salary during down times, resources and unrecoverable downtime. Moreover, costs including

human health and safety, financial penalties due to a breach of contracts, utility costs because

of a power interruption and loss of quality of semi-finished products. On the other hand,

indirect costs include costs of restoring a brand, loss of market share and postponement of

income or revenue of the organization.

In this project, power data was measured from the electrical system at Murdoch University

and saved in the form of spreadsheets. From these spreadsheets, calculations were done and

graphs plotted in order to identify the power quality issues experienced at the institution.

After identification of the power quality issues, the effect of these issues on parameters such

as voltage angle and phase, current angle and phase, temperature of the equipment was

determined either by calculation or visually from the plots of these parameters. These results

were then compared to the theoretical principles contained in the literature review section.


58

The results indicate that at the institution the power quality factors experienced are voltage

unbalance, current unbalance, distortion in current angle, harmonic distortion, and power

factor. Using both the IEC and NEMA methods, the percentage voltage unbalance was found

to be lower than the maximum set value of 2 %. As a result, this voltage unbalance would not

affect three-phase equipment in the system. However, the current unbalance was found to

be extremely high, and this is not safe for the equipment as it can result in heating and thus

degradation in windings of motor and transformers and a reduction of their efficiency. The

harmonic distortion measured from the institution that ranges between 1.8 and 2.8 % is lower

than the 5 % limit, and therefore is also safe for use with equipment. From these results, it is

clear that the power received at the institution is of high quality, and hence safe for use with

equipment. The major problem is the high current unbalance and the distortions in the

current angle. In fact, by using compensating device UPQC consequently should be employed

in the institution electrical network in order to decrease current unbalance and distortions of

the current angle.

The significant goal of this project of performing a power quality analysis at Murdoch

University to identify the causes of poor power quality and provide solutions to improve the

power quality as well as all the specific objectives that had been set before the

commencement of this research have all been achieved. Accordingly, both power consumers

and the electric utility will find this project of considerable significance. There will be a

decrease in the occurrence of power quality disturbances as through this project these

disturbances can be identified monitored, predicted, and mitigated thus power consumers

will benefit from less malfunctions of electronic devices. Less malfunctioned devices translate

to cost savings for the consumers because of the reduced repair and maintenance costs


59

required for malfunctioned devices. Since the power quality disturbances can be identified,

monitored, predicted, and mitigated through this project. Subsequently, industrial consumers

will benefit from lower interruptions of production. This translates to higher quality of

products, cost savings since idle time of personnel throughout the interruption would be

decreased, and the industry also benefits from less equipment damage. The electric utility

may gain considerable knowledge regarding their transmission, distribution network, and

sources of power quality disturbances in the electricity grid through this project. Therefore,

this project is of great significance to them.

5.1 Future Work Opportunities for the Power Quality Analysis at Murdoch

University

First of all, in the project presented in this thesis report, data was collected from the electrical

network of the institution and used to identify the power quality issues experienced at the

institution. Further work that can be conducted involves taking a detailed study of each power

quality issue identified and proposing a solution to decrease the power quality issue. After

installation of the proposed solution to the network, more tests should be carried out and

analysis of the test results done in order to prove the effectiveness of the proposed solution.

In addition, another further work that can be performed finds out the individual harmonic

order such as even order (2, 4, 6, 8) and odd order (3, 5, 7, 9). By doing this for all the power

quality issues identified, then we can conclusively say a problem was identified and a practical

and working solution presented to solve the problem. The conclusion will not be based on

theoretical information, but on proved and tested information.


60

Because of the increased adoption of the internet of things and automation in the world

currently. An algorithm can be developed that automatically computes and plots the power

quality issues from the data it receives from a power quality meter. The automated system

then transmits the computed data and plotted graphs to a power quality expert for further

action. In this system, the power quality meters will automatically send the data it measures

to a computer containing the algorithm. After processing the data, the computer will transmit

the processed information to an expert for further action. This algorithm can be designed in

such a way that it can be trained to monitor and even predict the occurrence of a power

quality issue. Furthermore, the algorithm can be designed to have additional functionalities

such as predicting failure of equipment in the network due to a reoccurrence of a power

quality issue.


61

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Department of Energy, "Eliminate Voltage Unbalance," Advanced Manufacturing Office,

Energy Efficiency and Renewable Energy, U.S Department of Energy, [Online]. Available:

https://www.energy.gov/sites/prod/files/2014/04/f15/eliminate_voltage_unbalanced_mot

or_systemts7.pdf. [Accessed 30 April 2018].

[63] A. McEachern, "Roles of Intelligent Systems in Power Quality Monitoring, Past, Present

and Future," in 2001 Power Engineering Society Summer Meeting. Conference Proceedings,

Vancouver- Canada, 2001.

[64] B. Singh, A. Chandra and K. Al-Haddad, Power Quality Problems and Mitigation

Techniques, West Sussex- UK: John Wiley and Sons Ltd, 2015.

[65] "EM133-R," Modbus Communications Protocol, Western Australia, 2018.


68

Appendix

Appendix Part A: EM133 Meter Manual


69

Figure 35: EM133 Meter Manual [65]


70

Appendix Part B: Calculation of Apparent Power and Power Factor

Taking the data for real power, apparent power, reactive power, and power factor for the

time 12:00:30 am, the authenticity of the measured results can be confirmed using the power

triangle.

Table 3: Power Data for the Phase A at 12:00:30 am

Parameter Value

Apparent power A 6.12 kVA

Reactive power A 2.37 kVAr

Real Power A 5.64 kW

Power factor 0.922

Apparent Power A = √(Real Power)2 + (Reactive Power)2 (35)

= √5.642 + 2.372 = 6.1177 kVA

Power Factor =Real Power

Apparent Power (36)

=5.64

6.12= 0.92157

Accordingly, the data from the meter is authentic and can be used for analysis of the power

quality issues.


71

Appendix Part C: Calculation of Voltage Unbalance

Based on the following equations:

UBF = √1 − √3 − 6β

1 + √3 − 6β∗ 100 (37)

Where:

β =|Vry|4 + |Vyb|4 + |Vbr|4

(|Vry|2 + |Vyb|2 + |Vbr|2)2 (38)

The IEC 61000 voltage unbalance was calculated as

Taking data 12:00:30 am, where

VA−B = 416.90, VB−C = 418.10, and VC−A = 417.50

Each of the phase to phase voltages above were raised to power 4 and to power 2 as detailed

by Table 4 below.

Table 4: Voltage Unbalance Using IEC 61000 Standard

Phase to Phase Voltage Voltage (x) (x)2 (x)4

VA-B 416.90 173,805.6100 30,208,390,067.4721

VB-C 418.10 174,807.6100 30,557,700,513.9121

VC-A 417.50 174,306.25 30,382,668,789.0625

From the values of Table 4, therefore using the equations in (37) and (38):

β =|VA−B|4 + |VB−C|4 + |VC−A|4

(|VA−B|2 + |VB−C|2 + |VC−A|2)2

=30,208,390,067.4721 + 30,557,700,513.9121 + 30,382,668,789.0625

(173,805.6100 + 174,807.6100 + 174,306.25)2

= 0.999994


72

Voltage unbalance thus is:

UBF = √1 − √3 − 6β

1 + √3 − 6β∗ 100 = √

1 − √3 − 6(0.999994)

1 + √3 − 6(0.999994)∗ 100 = 0.165984523 %

This was repeated for all the values of voltages collected every half second between 12:00:30

am up to 1:45:30 pm. Due to the huge amount of data, excel spreadsheet was used to

compute the voltage unbalance and to plot the voltage unbalance variation with time. A large

amount of data from the spreadsheet could also not be included in this section.

Appendix Part D: Risk Assessment

Various risks are associated with conducting this research. The major risk when conducting

this project is the risk of electric shock. Indeed, during the data collection stage, when

measuring the current, voltage, or frequency. There will be direct exposure to electricity thus

the risk of electrocution. Considerable care must therefore be taken and appropriate personal

protective equipment used throughout the measurement of the different electrical

parameters. Damaged and exposed live parts of the circuits must also be repaired.

Other risks related to the project include the use of computers during research and writing of

reports where there is a risk of losing data, illness, eye, and back strains because of the

computer glare and bad sitting posture. Treatment for these risks includes having a back up

of the research on external drives and cloud storage, using a portable computer when ill to

minimize movement to the laboratories and library and decreasing the computer brightness

in order to reduce eye strain cases due to computer glare. Taking frequent breaks and using

adjustable chairs is a solution to back strains caused by bad sitting posture.

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