Optimization of grounding grids design with evolutionary strategies [Elektronische Ressource] / von Sherif Salama Mohamed Ghoneim

Ghoneim

Informations

• Publié par: universitat_duisburg-essen
• Publié le: 01 janvier 2007
• Nombre de lectures: 25
• Langue: English
• Poids de l'ouvrage: 3 Mo

Extrait

 

Optimization of Grounding Grids Design with

Evolutionary Strategies

 

 

 

Von der Fakultät Ingenieurwissenschaften der

  Univeristät Duisburg-Essen

 

zur Erlangung des akademischen Grades eines

 

Doktor-Ingenieurs 

 

genehmigte Dissertation   Von   Sherif Salama Mohamed Ghoneim

 

aus

Kalubia-Ägypten

 

Referent: Prof. Dr. Ing. Holger Hirsch

Korreferent: Prof. Dr. Ing. Ignasi Colominas

Tag der mündlichen Prüfung: 19.11.2007

 

Abstract In order to achieve lightning protection and electromagnetic compatibility (EMC)

requirements, a proper grounding system is needed. Furthermore, the Earth Surface Potential

(ESP) due to discharging current into grounding system in case of abnormal conditions has to

be known.

I) 

II) 

The Main objectives of the grounding system are,

To guarantee the integrity of the equipments and continuity of the service under

the fault conditions (providing means to carry and dissipate electrical currents into

ground).  

To safeguard those people that working or walking in the surroundings of the

grounded installations are not exposed to dangerous electrical shocks.

To attain these targets, the equivalent electrical grounding resistance (R g ) of the system must be low enough to assure that fault currents dissipate mainly through the

grounding grid into the earth, while maximum potential difference between close points into

the earth’s surface must be kept under certain tolerances (step, touch, and mesh voltages).

A lot of efforts had been taken to answer the very important question, which is, how

the Earth Surface Potential due to discharging current into grounding system can be

calculated. Many researches are published to present information about step and touch

voltages, some of these publications depend on the experimental works on a scale model and

the other depend on some empirical function that de pend also on the results from

experimental.  

Scale model in an electrolytic tank to simulate the lightning events on earth is

presented to measure the Earth Surface Potential (ESP) on the surface of the water and also to

study the transient performance of the grounding grid when it subjects to lightning like

(Impulse current), in order to know something about the behaviour of the grid structure, i.e. is

there a transient behaviour that needs complex models or is a static model sufficient and also

give evidence to computer model. Impulse current tests were performed on 16(4 x 4) meshes.

On the other hand, an old, but still easy to implement technique depend on Charge

Simulation Method (CSM) is proposed to calculate the fields with the equivalent charges, the

attractiveness of the CSM, when compared with the Finite Element and Finite Difference

Method emanates from its simplicity in representing the equipotential surfaces of the

electrodes, its application to unbounded arrangements whose boundaries extend to infinity, its

ii

direct determination to the electric field and its calculation speed. The results of the method

are compared to experimental measurement results, empirical formulas in an IEEE standard

and also to the other technique like (Boundary Element Method) that is often used to calculate

Earth Surface Potential.

In the field of grounding system design, the optimization means to find a grounding

system which is able to safeguard those people that working or walking in the surroundings of

the grounded installations and on the other hand has minimal cost. A new technique

combining Evolutionary Algorithm with CSM field computation is proposed for optimization

the design of grounding grids. The basic design quantities of the grounding grids are the

ground resistance (R g ), touch voltage (V t ), step voltage (V s ) and the cost of the grounding system design. These mentioned quantities depend on the grid parameters, which are its side

lengths, radius of grid conductors and length of vertical rods.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

iii

Published papers [i] S. Ghoneim, H. Hirsch, A. Elmorshedy, R. Amer, “Improved Design of Square Grounding Grids”, International Conference Power System Technology, POWERCON2006, Chongqing, China, October 2006, pp. 1 – 4  . [ii] Ghoneim, H. Hirsch, A. Elmorshedy, R. Amer, “Surface Potential Calculation forS. Grounding Grids”, IEEE International Power and Energy Conference, PEcon2006, Putra Jaya, Malaysia, November 2006, pp. 501 – 505. [iii]  S. Ghoneim, H. Hirsch, A. Elmorshedy, R. Amer, “Effect of Profile Location on Step and Touch Voltages of Grounding Grids”, The Eleventh International Middle East Power Systems Conference, MEPCON2006, Elmenia, Egypt, December. 2006. [iv]  S. Ghoneim, H. Hirsch, A. Elmorshedy, R. Amer, “Quality Model for Optimum Design of Grounding Grid”, 1 st International Power Engineering and Optimization Conference, PEOCO2007, Shah Alam, Malaysia, June. 2007. [v] S. Ghoneim, H. Hirsch, A. Elmorshedy, R. Amer, “Optimum Grounding Grid Design by Using an Evolutionary Algorithm,” IEEE General Meeting, Tampa, Florida, USA, June 2007. [vi] S. Ghoneim, H. Hirsch, A. Elmorshedy, R. Amer, "Charge Simulation Method for Finding Step and Touch Voltage", 15 th ISH2007, Slovenia, August 2007. [vii] S. Ghoneim, H. Hirsch, A. Elmorshedy, R. Amer, "Measurement of Earth Surface Potential Using Scale Model", UPEC2007, Brighton University, England, September 2007.      

                      iv

 



 



 

 



 

 

 

 

 

 

 

 

 





























 



 



 

 

 

 













 





 



 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

v

 

 

Acknowledgements 

On the occasion of finishing my PhD study, it gives me immense pleasure to express my

gratitude to all the people who have supported me and contributed to my work.

I hope to submit my great thanks to Prof. Holger Hirsch, the head of the Energy

Transmission and Storage Institute, Duisburg-Essen University, for all efforts, cooporations,

supports and encouragements to finish this thesis. I did not find any words to express my

feeling towards him but I think that he is a good father doctor for me.

I am grateful to one of my best guidance for the work, Prof. Ignasi Colominas from the

Civil Engineering School of the University of La Coruna (Spain), for all his fruitful

discussions, cooporations and encouragement during my study.

The help and assistance from all persons work in the Energy Transmission and Storage

Institute- Duisburg-Essen University is greatly appreciated.

In the last, I would like to thank my wife for supporting me in all that I did. Also this

thesis is written for my daughter and son, thanks for all persons in my wife’s Family and a lot

of thanks to my parents who pray for me to finish this thesis.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

vi

ulation using n umerical methods

 1.2.3 Earth Surface Potential calculation using s cale model

 

1.2.2 Earth Surface Potential calc

 

Chapter 2: Terminology and Definitions

2.1 Definitions

 

Contents

1.1 The role of grounding systems in lightning protection

1.2 Overview of Earth Surface Potential calculation

Chapter 1: Introduction

 

 

1.2.1 Earth Surface Potential calculation using e mpirical formulas

 

 

4.1 Boundary Element Method

 

4.2 Charge Simulation Method

Calculation results using BEM

Chapter 5: Calculation Results

5.1.1 Importance of vertical rods addition to gro unding grid

5.1

3.1 Scale model with scaling time of the applied impulse current

Chapter 3: Experimental Investigations

3.3 Test results

 

3.2 Test setup

 

Chapter 4: Methods of Calculation

 

 

49

5.2

5.2.1 Effect of the number of meshes on the earth surface potential

touch voltages

Calculation results using CSM

 

 

44

5.1.3 Effect of the profile location on the grid resistance, step and

5.1.2 Effect of the vertical rods location on the step and touch voltage

 

 

 

 

43

5.2.3 Effect of grid depth on the earth surface p otential

potential

28

36

36

38

43

43

50

46

 

 

 

 

 

5.2.2 Effect of the vertical rods and its length on the earth surface

55

 

 

 

 

(Charge Simulation Method)

Chapter 6: Optimization of Grounding Grids Design Based on Evolutionary

  58

52

53

5.3 Validation of the Charge Simulation Method

5.4 Comparison between the experimental and theore tical calculation by

 

52

5.2.4 Effect of number of point charges on the ea rth surface potential

 

21

17

23

21

5

17

1

1

11

 

13

5

 

 

 

 

vii

Strategy

49

 6.1 Evolutionary Algorithm (Optimizer)  6.2 Numerical Example Chapter 7: Conclusions  References   

                                               

 

 

 

viii

59 63 66 69