ANALYSIS OF GROUNDING AND HARMONICS IN POWER QUALITY

ISSUES

WANNURZANA TAN NYUK MAY

A thesis submitted in fulfilment of the

requirements for the award of the degree of

Bachelor of Electrical Engineering

Faculty of Electrical Engineering

Universiti Malaysia Pahang

NOVEMBER 2010

ii

I declare that this thesis entitled “Analysis of Grounding and Harmonics in Power

Quality Issues” is the result of my own research except as cited in the references.

The thesis has not been accepted for any degree and is not concurently submitted in

candidature of any other degree.

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

Name : Wannurzana Tan Nyuk May

Date : 29 NOVEMBER 2010

iv

ACK�OWLEDGEME�TS

I am grateful and would like to express my sincere gratitude to my supervisor

Mr Omar bin Aliman for his germinal ideas, invaluable guidance, continuous

encouragement and constant support in making this project possible. I am truly

grateful for his progressive vision, his tolerance of my naïve mistakes, and his

commitment to my future career. His encouragements, guidance and supports from

the initial to the final level enabled me to develop an understanding of the project. He

continually and convincingly conveyed a spirit of adventure in regard to research,

and an excitement in regard to teaching. Without his guidance and persistent help

this dissertation would not have been possible. I also sincerely thanks for the time

spent proofreading and correcting my many mistakes.

My sincere thanks also go to all the lecturers and staffs of the Electrical

Engineering Department and JPPH of Universiti Malaysia Pahang, who helped me in

many ways. Unfortunately it is not possible to list all of them in this limited space. I

acknowledge my sincere indebtedness and gratitude to my parents for their love,

dream and sacrifice throughout my life. Lastly, I offer my regards and blessings to all

of those who had supported me in any respect during the completion of the project.

v

ABSTRACT

The purpose of this thesis is to present the importance and affects of

grounding and harmonics to the quality of power. In this case, data center is referred

as a case study for the analysis of grounding and harmonic. These power quality

issues are very important in data center where it might cause severe failure operation

systems. For the investigation of the quality of the power in data center, electrical

disturbance log is done to examine the quality of grounding and characteristics of

harmonics profiles in the data center. The power monitoring instrument used was

Fluke 1750 Recorder and the data recorded was analyzed by using Fluke 1750

Analyze.. The power quality conditions of the data center significantly depends on

the every aspect in electrical system such as voltage, current, frequency, power,

power factor and so on. As the result of this analysis, the grounding conditions used

in the data center was found to have no signs of severity in power quality conditions.

However, there were some issues of improper wiring and grounding found in the

data center. This will be discussed in this thesis. On the other hand, the harmonic

distortion in data center were discussed in terms of the source of harmonics and

effects of harmonic on the performance of data center. In order to identify the cause

of such orders of harmonics in this system, the most non linear load is identified.

Therefore, some recommendations and mitigations of the harmonics were discussed.

vi

ABSTRAK

Objektif untuk tesis ini adalah untuk membentangkan kepentingan dan kesan-

kesan sistem pembumian dan harmonik terhadap kualiti kuasa elektrik. Oleh itu,

pusat pangakalan data telah dijadikan sebagai kes kajian dalam kajian terhadap

sistem pembumian dan harmonik. Isu-isu kualiti tenaga ini adalah amat penting

untuk pusat pangkalan data kerana ia mampu mengakibatkan kegagalan operasi yang

serius sekiranya ia tidak diatasi. Untuk kajian profil kuasa di pusat pangkalan data,

rakaman gangguan tenaga elektrik telah dilakukan untuk memperhatikan keadaan

sistem pembumian dan ciri-ciri harmoniknya. Fluke 1750 Recorder digunakan untuk

merekod data dan data yang telah direkod dianalisis dengan menggunakan Fluke

Power Analyze. Keadaan kualiti tenaga di dalam pusat pangkalan data bergantung

kepada semua aspek dalam sistem elektrik iaitu voltan, arus, frequensi, kuasa, faktor

kuasa dan sebagainya. Keputusan daripada analisis ini menunjukkan bahawa sistem

pembumian yang diguna dalam pusat pangkalan data tidak mempunyai sebarang

masalah yang kritikal terhadap kualiti tenaga. Walaubagaimanapun, terdapat

beberapa isu mengenai ketidaksesuaian pemasangan dan pembumian. Ini akan

dibincangkan dengan teliti dalam tesis ini. Selain itu, distorsi harmonik dibincang

secara menyeluruh mengenai sumber harmonik kesan-kesannya terhadap prestasi

pusat pangkalan data. Untuk mengesan penyebab berlakunya turutan-turutan

harmonik tersebut, beban non linear dikenal pasti. Oleh itu, penambahbaikan untuk

harmonik dibincang.

vii

TABLE OF CO�TE�TS

CHAPTER TITLE PAGE

DECLARATIO� ii

DEDICATIO� iii

ACK�OWLEDGEME�TS iv

ABSTRACT v

ABSTRAK vi

TABLE OF CO�TE�TS vii

LIST OF TABLES xii

LIST OF FIGURES xiv

LIST OF SYMBOLS xix

LIST OF APPE�DICES xxi

1 I�TRODUCTIO�

1.1 Background of Study 1

1.2 Problem Statement 2

1.3 Objectives 3

1.4 Scope and Limitation of Study 3

1.5 Significance of Study 4

2 LITERATURE REVIEW

2.1 Power Quality 5

2.2 The Fundamentals of Grounding System 10

viii

2.2.1 Purpose of Grounding System 10

2.2.2 Types of Grounding System 11

2.2.2.1 TT System 13

2.2.2.2 TN-C System 13

2.2.2.3 TN-C-S System 14

2.2.2.4 TN-S System 15

2.2.2.5 I-T System 15

2.2.3 Grounding System in Data Center 16

2.2.4 Problems Manifested in Grounding System 17

2.2.4.1 Insulated grounds 18

2.2.4.2 Ground loops 18

2.2.4.3 Missing safety ground 19

2.2.4.4 Multiple neutral-to-ground bonds 19

2.2.4.5 Additional ground rods 20

2.2.4.6 Insufficient neutral conductors 21

2.2.5 Effects of Improper Grounding System 21

2.3 Harmonic 23

2.3. 1 General Principles 22

2.3. 2 Harmonic Sources 25

2.3.3 Effects of Harmonic Distortion 26

3 RESEARCH METHODOLOGY

3.1 Introduction 29

3.2 Systematic Power Quality Study 30

3.3 Summary 32

4 RESULTS A�D DISCUSSIO�

4.1 Introduction 33

4.2 Grounding System in data center 33

4.3 Harmonic Analysis 41

4.4 Characteristics of Power System 48

ix

5 CO�CLUSIO� A�D RECOMME�DATIO�

5.1 Conclusions 53

5.2 Recommendations 54

REFERE�CES 55

APPE�DICES 56

xi

LIST OF TABLES

TABLE �O

TITLE PAGE

2.01 Categories of power quality events with durations and

voltage magnitude

7

2.02 Power quality events 8

2.03 Effects of Harmonics on Equipment 25

3.01 Time, data and locations of the data logged 31

4.01 Voltage Distortion Limits 43

4.02 Current Distortion Limits 44

xii

LIST OF FIGURES

FIGURE �O TITLE PAGE

2.01 CBEMA Standards 6

2.02 ITIC Standards 6

2.03 Schematic diagram of TT System 13

2.04 Schematic diagram of TN-C System 14

2.05 Schematic diagram of TN-C-S System 14

2.06 Schematic diagram of TN-S System 15

2.07 Schematic diagram of IT System

15

2.08 Separately Derived System 17

2.09 Ground Loops Current 19

2.10 Neutral current flow with and extra neutral-to-

ground bond

20

2.11 Balanced three phase system 21

2.12 Distorted waveform composed of fundamental,

5th and 7th harmonics

24

2.13 Example of total harmonic distortions 25

2.14 Examples of harmonic sources 26

3.01 Systematic Power Quality Study 30

4.01 Main grounding at LV Switch Room 34

xi

4.02 Coiled wire grounding conductor for cabinets

and racks at Data Centre

34

4.03 Two different ways of grounding wire

connection

35

4.04 Typical grounding system map in Data center 37

4.05 Zero Ground Current in data center 38

4.06 Ungrounded system fault 39

4.07 Single line-to-ground fault 40

4.08 Neutral current in data center 41

4.09 Recorded Harmonic Spectrum of Voltage 42

4.10 Recorded Harmonic Spectrum of Current 42

4.11(a) Peak hour of Harmonic Spectrum in data center 44

4.11(b) Night time of Harmonic Spectrum in data center 45

4.12(a) Day time of Harmonic Spectrum in lecture halls 45

4.12(b) Night time of Harmonic Spectrum in lecture

halls

46

4.13(a) Day time of Harmonic Spectrum in computer

room

46

4.13(b) Night time of Harmonic Spectrum in computer

room

47

4.14(a) Current waveform of one computer 47

4.14(b) Current waveform of two computers 47

4.14(c) Current waveform of three computers 48

4.15 Current’s waveform in data center 49

4.16 Red-phase is heater than other two phases 49

4.19 Neutral to ground voltage’s waveform in data

center

50

4.20 Ground current’s waveform in data center 51

xii

4.21 Power factor in data center 52

xi

LIST OF SYMBOLS

I - Current

V - Voltage

Z - Impedance

L - Inductance in µH

r - Radius of coil in inches

$ - Number of turns

D - Length of coil in inches

f - Frequency

xii

LIST OF APPE�DICES

APPE�DIX TITLE PAGE

A Single Line Diagrams 56

B

Experiment Pictures

60

CHAPTER 1

I�TRODUCTIO�

1.1 Background of Study

Power quality in electric networks is one of today's most discussed topic in

electrical engineering but also one of the most problematic subject as it became one

of the main devastating problem in the supply network. As we connect more

electrical equipment to our power systems, the quality of the power becomes more

important. Power quality issues can be very high-speed events such as transients,

harmonic, high frequency noise, faulty wiring of grounding system, voltage swells

and sags and total power loss. In this thesis, grounding and harmonics will be

discussed in terms of power quality. Grounding may not be complicated but when a

lack of understanding mixes with folklore and tradition, it may become exceedingly

complex. It has been reported that 80 to 90% of power quality problems are mostly

caused by improper wiring and grounding. Grounding is defined as a conducting

connection, whether intentional or unintentional by which an electric circuit or

equipment is connected to the earth or to some conducting body relatively large that

serves in place of the earth. Grounding system designs and operations are completely

depends on the applications in particular requirements. By specializing the grounding

techniques can evolve the complexion of grounding system topic to meet the

perceived grounding requirements of electronic equipment.

2

Another power quality issue is harmonic. Harmonic is defined as sinusoidal

component of a periodic waveform having a frequency that is an integer multiple of

having fundamental frequency. It is also a mathematical model that used to analyzed

distorted waveforms and can be generated by non linear electronic loads. The

harmonic related losses reduce system efficiency, cause apparatus overheating, and

increase power and air conditioning costs. The harmonic currents can have a

significant impact on electrical distribution systems and the facilities they feed. As

the number of harmonics producing loads has increased over the years, it has become

increasingly necessary to address their influence when making any additions or

changes to an installation.

1.2 Problem Statement

Data center today are designed with systems and redundacies to minimize the

loss of power. However, the important issue to be emphasized is the quality power.

Grounding of the data center is one of the ways to make sure the performance of the

data center is always maintained at the acceptable level. Data center is dealing with

many electronic equipments that often run into harmonic issues and the it should be

taken care of by mitigating the harmonics.

1.3 Objectives

• To identify and analysis the types of grounding systems used

according to the application of the utilities.

3

• To determine and analysis the harmonic profiles of the Block

A(Admistrative Block) in FKEE, UMP.

1.4 Scope & Limitation of Study

This research was focused on the grounding system and characteristics of

harmonics of data center in Block A, FKEE. Block A is more known as the

Administrative Block, consists of many functional rooms such as computer lab, data

center, lecture halls, cafe and so on. In this case, the attention was only brought to the

three locations which were lecture halls, data center and computer lab. These three

locations were selected because they were mostly used during day time. To

determine both grounding system and harmonic profiles, one of the effective way

was to apply a systematic power quality study. The basic of systematic power

quality study involves the electrical disturbance logs, site survey and installation of

power quality monitoring instruments. In this study, the methodology of each step in

the power quality study will be explained in the Chapter 4. Moreover, the literature

reviews of this thesis were also used as part of the references of this study. It helped

in gaining the understanding in grounding system designs specifications,

requirements and calculations. On the other hand, the harmonics studies were based

on the electrical disturbance logs. However, there are limitations for the grounding

and harmonic analysis, which are listed below:

(a) The modification of the grounding system in the data center.

(b) Any modification to the data center that has to be related to reduce harmonics.

Therefore, only suggestions or recommendations for the improvement of the power

quality in the data center will be discussed in this thesis.

4

1.5 Significance of Study

Grounding system is designed for many purposes. The purpose of the system

grounding is to control the voltage with respect to earth, or ground within the

predictable limits and to provide a flow of current that will allow detection of an

unwanted connection between system conductors and ground. Such detection may

then initiate operation of automatic devices to remove the source of voltage from

these conductors. In today’s eletrical environment, buildings that are separated by

large physical distances are typically tied together via a communication circuit.

Grounding is a common issues that can be classified as system grounding, protective

grounding, source grounding, equipotential grounding and so on. Each of these

groundings bring the same purpose which is for the personnel safety. On the other

hand, harmonic is generally defined as a distortion of the normal electrical current

waveform which were generally transmitted by non linear loads. The examples of

non linear loads are such as switch-mode power supplies (SMPS), variable speed

motors and drives, personal computers, laser printers, fax machines, battery chargers

and UPS. Harmonic currents can have a significant impact on electrical distribution

systems and the facilities they feed. In some cases, the harmful effects of harmonic

might be only found after an actual failure occurs, which is why the transformer that

have operated satisfactorily for long periods have failed in a relatively short time

when plant loads were changed or a facility’s electrical system was reconfigured.

Harmonic resonance also can cause the substantial damage to the electrical

equipment. Resonant conditions are created when the inductive and capacitive

reactance become equal in electrical system. It is important to consider the impact of

harmonics when contemplating additions or changes to a system.

CHAPTER 2

LITERATURE REVIEW

2.1 Power Quality

Power quality is defined as any deviation from normal of a voltage source

(either DC or AC). Each type of electrical equipment will be affected differently by

power quality issues. A power quality problem existence can be determined by

analyzing the electrical power and evaluating the equipment or load. Power quality

problems have many names and descriptions. It can be surges, swells, transient,

flickers, harmonics and so on. They are divided into short duration, long duration,

and continuous categories. The standards used for power quality studies are the

CBEMA curve (Computer Business Equipment Manufacturing Association), which

were then changed to ITIC(International Techonology Industry Council). These

standards are shown in the Figure 2.01 and 2.02. The various power quality events

are plotted on the curve based on time and magnitude in both the figures below. Any

event outside the curve would be a suspect of power problem.

6

Figure 2.01 CBEMA standards

[Source: http://www.itic.org/clientuploads/Oct2000Curve.pdf]

Figure 2.02 ITIC Standards

[Source: http://www.itic.org/clientuploads/Oct2000Curve.pdf]

7

For grounding system, the standard used in the data center is refered to JKR

standard. However, JKR standards were found almost similar to the NEC(National

Electrical Code) standard. Therefore, both standards were used to study the

grounding system applied in a data center (refer JKR standard in the appendix). The

standard used for harmonic analysis was IEEE Recommended Practices and

Requirements for Harmonic Control in Electrical Power Systems(IEEE 519-1992).

In this standard, it described about how harmonics produced in non linear loads such

as computers and SMPS equipment which can be found in data center, lecture halls

and computer rooms and also the harmonic controls and mitigation.

Table 2.01: Categories of power quality events with durations and voltage

magnitude

8

Instead of grounding system and harmonics, other power quality issues were

also discussed briefly in this thesis. Table 2.01 shows the categories of power quality

events with durations and voltage magnitude that usually can be found in the

electrical system and Table 2.02 is the examples of few power quality events that

mainly discussed in the electrical power system.

Table 2.02: Power quality events, waveforms and descriptions

Events Waveform Description

Harmonics

Transient

Harmonics are a recurring

distortion of the waveform that

can be caused by various

devices including variable

frequency drives, non-linear

power supplies and electronic

ballasts. Symptoms of

harmonic distortion include

overheating and equipment

operational problems.

Transients are very short

duration (sub-cycle) events of

varying amplitude. Transients

are probably most frequently

visualized as the tens of

thousands of volts from a

lighting strike that destroys

any electrical device in its

pathand it can be caused by

equipment operation or failure

or by weather phenomena like

lightning.

9

Sag or Dip

Swell

Notching

Sags account for the vast

majority of power problems

experienced by end users.

They can be generated both

internally and externally from

an end users facility.

A swell is the opposite of a

sag. Although swells occur

infrequently when compared to

sags, they can cause equipment

malfunction and premature

wear. Swells can be caused by

shutting off loads or switching

capacitor banks on.

Notching is a disturbance of

opposite polarity to the normal

voltage waveform (which is

subtracted from the normal

waveform) lasting for less than

one-half cycle. Notching is

frequently caused by

malfunctioning electronic

switches or power

conditioners.

10

Undervoltage

Undervoltage is a decrease in

voltage below 90% of its

nominal value for more than

one minute. Undervoltage is

sometimes called a "brownout"

although this term is not

officially defined. Brownout is

often used when the utility

intentionally reduces system

voltage to accommodate high

demand or other problems.

2.2 The Fundamentals of Grounding System

2.2.1 Purpose of Grounding System

Data centers have some very specific and unique requirements for grounding

and bonding that differ significantly from the typical electrical distribution system in

other types of facilities. These include the grounding and bonding of equipment in

the data center and grounding of the building distribution system. The NEC requires

grounding for three main reasons, which are safety, overcurrent operation and

equipment operation: