MSC OF IGs

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Grid-connected Induction Generators with Reference to Potential Small

Power Plant Developments in Sudan

By:

SALIH AHMED OBEID SALIH

B. Sc. (Honors) in Electrical Engineering, University of Khartoum, 1981

A Thesis Submitted to the Graduate College, University of Khartoum in

Partial Fulfillment for the Award of the Degree of M. Sc. in

Electrical Power Engineering

Supervisor: Dr. Fayez Mohammed El-sadik

Co-supervisor: Dr. Kamal Ramadan Doud

DEPARTMENT OF ELECTRICAL & ELECTRONIC ENGINEERING

FACULTY OF ENGINEERING

UNIVERSITY OF KHARTOUM

February 2013


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I

DEDICATION

I would l ike to dedicate this work to my famil y starting with the loving

Memories of my father , and to my mother Aeisha Salim I dri s who

Helped and supported me very much and to my wife Sauad Hamid

Mahadi who stood beside me all the time of thi s project and my love.

To my chi ldren, Ahmed, Elhar ith , Leena, Hammam, Alaa, and Mohammed.

Salih


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II

Acknowledgement

I am very grateful to my supervisor Dr. Fayez Mohammed EL-Sadik

for his patience and guidance throughout the development stages of this

project. His valuable suggestions, ideas, concepts and advices are greatly

appreciated.

My thanks are also extended to the former National Electricity Corporation

(NEC) administration for their financial support during the initial stages of

the M. Sc. project.

Special thanks are due to the former gas turbine department manager,

Roseires hydro power station manager, Jebel Aulia hydro matrix power

station manager and his staff and to the technicians of Dr. Sherif thermal

power station who have greatly assisted with the experimental test bed.

Last but not least, my deepest thanks are extended to the faculty of

engineering electrical machines laboratory staff.


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III

Abstract

The study aimed to investigate the possibility of generating small isolated

(stand- alone) or connected power to the national grid.

The studytook Jebel Aulia hydro matrix turbines as a study. The detail of the

induction generators-based project which is supplying the national grid with

30 MW of power with the minimum of running cost was described.

A hard procured testbed was installed at the electrical laboratory at the

faculty of Engineering to mimic steady state performance characteristic of the

induction generators.

The induction generator was operated above its rated synchronous speed

then the national grid was fed with 1.8 kW at three phase supply voltage of

220 V, 50 Hz and power factor of 0.82 which was further improved to be 0.98

by means of capacitor banks. The results showed that these kinds of induction

generators need neither DC excitation nor speed governing system as that

used for conventional AC synchronous generators and hence considerable

reduction of cost and size was achieved.

The survey proposed the potential sites to install small hydro power

generators to increase electric production in Sudan


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IV

30

.

/. 1.8

0 220 0.2 0.8

. .


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V

LIST OF CONTENTS

DEDICATION........................................................................................................ I

Acknowledgement.................................................................................................. II

Abstract ................................................................................................................ III

.................................................................................................................. IVChapter One........................................................................................................... 1

I.1 General: ......................................................................................................... 2

I.2 Sudan Installed Generation Capacity: ............................................................ 2I.3The Jebel Aulia Dam: ..................................................................................... 3

I.4 The Induction Generator Alternative: ............................................................ 4

I.5 Thesis Layout: ............................................................................................... 5

Chapter Two .......................................................................................................... 7

Grid Connected Induction Generators for Small Hydro: ..................................... 8

THE JEBELL AULIA EXAMPLE ..................................................................... 8

2.1 Technical Description: .................................................................................. 8

2.2 Reasons for the Induction Generator Alternative: ....................................... 15

2.3 System Protection: ...................................................................................... 17

2.4 Power Station Performance:........................................................................ 21

Chapter Three ...................................................................................................... 25

Equipment Procured for Laboratory Induction Generator Tests ........................... 28

3.1 General: ...................................................................................................... 28

3.2 Induction Generator Test Equipment: ....................................................... 29

3.3 Measurement of Induction Motor Parameters: ............................................ 36

Chapter Four........................................................................................................ 41


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VI

Steady-State Performance Measurements and Calculations ................................. 44

4.1 Calculations and Measurements - Laboratory Tests: ................................... 44

4.2 Power-factor Calculations Procedure: ......................................................... 51

4.3 Calculations and Measurements for the Jebel aulia Hydro - matrix UnitsTests: ................................................................................................................ 54

Chapter Five ........................................................................................................ 64

Recommended Sites of Small Power Generation in Sudan................................... 67

5.1 Utilization of Induction Motors and old Synchronous Generators:.............. 67

5.1.1 Kilo-X gas turbine power station: ...................................................... 68

5.1.2 Burri II Power Station: ......................................................................... 68

5.1.3 Burri III Power Station:......................................................................... 69

5.1.4 Kashm Elgirba Rehabilitation Project: ............................................... 69

5.2 Potential for Small Hydro Power Schemes:................................................ 70

Chapter Six .......................................................................................................... 85

CONCLUSIONS AND RECOMMENDATIONS ............................................... 86

6.1 General ....................................................................................................... 89

6.2 The advantages of the experience:............................................................... 91

References: .......................................................................................................... 93


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VII

LIST OF FIGURES

Figure (2.1) View of three modules of the hydro matrix turbine 8

Figure (2.2) View of one module (two turbines and generators) 9

Fig (2.3) Connection to the National Grid 10

Fig.(2.4) Another view of the feeders seen on the PLC display with Z705 and

Z8o5 11

Fig (2.5) Single-Line Diagram of Jebel Aulia S/S 12

Fig (2.6) Connection Layout of the two generators (courtesy of VA TECH

HYDRO) 13

Fig.(2.7) View of one turbo generator 14

Fig (2.8) General arrangement of Somatic S7-300 PLC 16

Fig (2.9) Layout of PV/WTG interconnected with EU and control strategy 18

Fig (2.10) The electric drawing of one module 19

Fig (2.11) Compensating circuit in 5 steps 20

Fig (2.12) Shunt capacitors connected in series with the inductance to remove the


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harmonics (courtesy of VA TECH HYDRO) 21

Fig (3.1) 5.5KW DC motor-2.0 hp Induction Motor Generator Set 27

Fig (3.2) 5.5 KW DC motor-1.0 hp Induction Motor Generator Set 28

Fig (3.3) Power-factor Correction Capacitor Bank of 18 F units 29

Fig (3.4) Rheostats ofdifferent sizes for dc motor speed control 30

Fig.(3.5) The speed indicator of the 2 hp motor in r.pm. 31

Fig (3.6) A View of the power quality analyzer (Fluke 434) 31

Fig.(3.6) DC-Motor Prime-mover Arrangement for Induction Generator

Experiments 33

Fig (3.7) Stator winding resistance measurements 34

Fig.(3.8) No-load test display data of the 2 hp motor 35

Fig.(3.9) Locked-rotor test display of the 2 hp motor 36

Fig (3.10) Equivalent circuit of No load test 37

Fig (3.11) Equivalent circuit of locked rotor 37


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Fig.(4.1) Zero-slip 2hp motor test data 42

Fig.(4.2) Generated Power Display = 1.8 KW 43

Fig. (4.3) 2hp motor data display as generator 43

Fig (4.4) The 2hp motor as a generator with capacitor banks 44

Fig.(4.5) Active power /speed curve of the 2 hp motor 44

Fig.(4.6) Torque /speed curve of the 2hp motor 45

Fig.(4.7) Reactive power/speed curve of the 2 hp motor 45

Fig.(4.8) Power factor/speed curve of the 2 hp motor 46

Fig.(4.9) Efficiency /speed curve of the 2 hp motor 46

Fig(4.10) The 2 hp motor with capacitors in series 47

Fig.(4.11) The 2 hp motor with capacitors in series 47

Fig.(4.12) The harmonic contents of the 2 hp motor 48

Fig.(4.13) The red phase current harmonic content 48


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Fig.(4.14) The yellow phase current harmonics content 49

Fig.(4.15) The blue phase current harmonics content 49

Fig.(4.16) Harmonics content of all three phase currents 56

Fig.(4.17) Wave ofthe three phase currents 56

Fig (4.18) Wave of the three phase voltage 57

Fig.(4.19) Power and energy of the induction generator 57

Fig.(4.20) Harmonic contents of the currents 58

Fig.(4.21) Volt/amp/hertz of the induction generator 59

Fig.(4.22) Display of the current waveform 59

Fig.(4.23) Display of the voltage waveform 59

Fig.(4.24) Power and energy of the induction generator 60

Fig.(4.25) Another display of power and energy of the induction generator 60

Fig.(4.26) Harmonic table for the three phase currents 61


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Fig.(4.27) Active power/speed curve 61

Fig.(4.28) Reactive power/speed curve 62

Fig.(4.29) Power factor/speed curve of the Jebel Aulia motor ..62

Fig.(4.30) Torque /speed curve of Jebel IG 63

Fig.(4.31) Simulation of capacitors connected in series 63

Fig.(4.32) Simulation ofcapacitors connected in series 64

Fig (5.1) Downstream view of Sennar dam 71

Fig (5.2) Another view of Sennar dam 71

Fig (5.3) Kilo 0 of Sennar dam 72

Fig (5.4) Kilo 77 of Jazeera Canal 72

Fig (5.5) Kilo 57 bridge of Jazeera Canals 73

Fig (5.6) Kilo 77 on Jazeera Canal (side view) 74

Fig (5.7) Kilo 57 bridge of Managil Canal 75


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Fig (5.8) Kilo 57 on Managil Canal 75

Fig (5.9) AbuRakham dam 78

Fig (5.10) View No 2 of AbuRakham dam ...79

Fig (5.11) Kilo 22 Bridge on Rahad Canal 80

Fig (5.12) Kilo 36 bridge on Rahad Canal 81

Fig (5.13) View no.2 of kilo 36 bridge 82

Fig (5.14) Kilo 76 bridge of Rahad Canal 83

Fig (5.15) View no.2 of kilo 76 bridge of Rahad Canal 84

Fig (6.1) Typical arrangement of canal fall small hydropower station 88

Fig (6.2) Typical arrangement of small hydro power station 89

Fig (6.3) Another typical arrangement of small hydro power station .89

Fig (6.4) Kalmoni 200 kW SHP project near Guwahati in Assam 90


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LIST OF TABLES

Table (3-1) Results of the no load test and blocked rotor test 36

Table (3.2) Rules of thumb dividing rotor and stator reactance 39

Table (4.1)The required KVAR of the capacitor for power factor correction..50

Table (5.1) Data from Elmanagil project 76

Table (5.2) Data from Aljazeera project 77

Table (5.3) Data from Elrahad project 85


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LIST OF APPENDICES

APPENDIX A A

APPENDIX B M

APPENDIX C N

APPENDIX D O

APPENDIX E E


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CHAPTER I

INTRODUCTION


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Chapter One

I.1General:

In the National Energy Plan of 1985 and the National Strategy Plan of

1992, the power sector objectives of Sudan were formulated. The plan of a

hydro matrix power plant implementation at the Jebel Aulia Dam is fully in

line with these objectives; in particular, the emphasis on the development of

hydroelectric generation together with the provision of electricity at lowest

possible cost, which can be fully met with this technology aiming at less civil

construction, little excavation and no coffer dams, no additional land usage,

and the maintenance of existing river flow patterns.

I.2 Sudan Installed Generation Capacity:

Sudan currently has an installed electricity generation capacity of 2588 MW,

managed by the ministry of dams and electricity. It is composed of the

thermal (mainly furnace) and hydropower plants. Hydroelectric power

generation varies greatly over time, due to rainfall patterns. The maingenerating facility of hydro power is the Merowi dam located on the Main

Nile river basin approximately 430 km north of Khartoum with ten

generating units of a total 1250 MW. Roseires has an installed capacity of 280

MW, but its output varies greatly as water levels on the river rise and fall

throughout the year.

VA-Tech-Hydro Hydro-matrix coordinator Herald Schmidt said: "The

excellent business relation between NEC and VA-Tech-Hydro goes back to

1968, when NEC ordered the original equipment for the Roseires hydropower

plant. The original turbines were supplied and installed by VA-Tech-Hydro

for NEC and just recently VA-Tech-Hydro has been awarded contracts to


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rehabilitate these turbines. The modernization and rehabilitation of the

turbines became necessary because of the wear and tear caused by the

aggressive and heavy silt load of the Blue Nile"1.

Schmidt continued: "The continuous engagement at the Roseires power

station has led to the formation of an informal partnership between NEC and

VA-Tech-Hydro under which VA-Tech-Hydro provides supplies, expert

services and consultations in order to effectively support and assist NEC in its

effort to maintain and improve electricity supply to Sudan's growing economy

and private consumers".

I.3The Jebel Aulia Dam:In the year 2001, VA-Tech-Hydro received its first large contract for a

Hydro-matrix power plant. The contract was placed by the former National

Electricity Corporation (NEC), the Sudanese state owned electricity producer

and distributor. The total contract value was worth 30 million Euros. NEC

awarded VA Tech Hydro with the supply of 40 Hydro-matrix power modules,

each with two turbine generator sets, for 40 of the 50 openings of the Jebel

Aulia dam on the White Nile in Sudan about 40 km south of the capital,

Khartoum. The contract also included the required mechanical and electrical

auxiliary systems as well as a new dam crane.

The Jebel Aulia dam was built in 1933-37 and is used mainly for irrigation

purposes and flood control. In March 2004 the first 20 Hydro-matrix turbines

were handed over to the customer for commercial service and have been

1Power Engineering International magazine, June 2004.


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supplying electricity into the grid of NEC. Installation work on the next units

is already in full swing, every two months ten turbine generator units were

commissioned.

Full operation of the power plant was scheduled for early 2005. The new

Hydro-matrix power plant at Jebel Aulia has contributed considerably with

30.4 MW to the generation capacity in Sudan by means of environmentally

clean hydropower.

Financing was one of the key issues of the project. At the time, bank

guarantees to the satisfaction of VA Tech Hydro could not be obtained, butwith a special procedure this problem was solved. It was agreed with the

customer that periodical payments would be made, while VA Tech Hydro will

only perform according to milestone events. This procedure has turned out to

be the best for both parties and is based on the long lasting excellent

relationship and particularly with the previous National Electricity

Corporation (NEC) which is the main supplier together with the new

generation of Merowi Dam power station which is implemented by the Dam

Implementation Unit(DIU) and adding a power of 1250 MW to the national

grid of Sudan which is already having a power of 1338 MW, where an

efficient electrical energy of 30 MW has been obtained from Jebel Aulia

Hydro matrix power station as described below.

I.4 the Induction Generator Alternative:

Engine driven induction generators were ideal power sources for those

industries and farmers required to curtail their demands during the power


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shortage in northern California in the spring of 19482.

The advantages of the

induction generator were: control apparatus simplicity, freedom from

hunting, neither excitation nor synchronization requirements, low fault

currents, low cost, and subsequent general usefulness in later motor

applications.

The nameplate data on most induction machines would be those of motor

ratings, and it is desirable to consider what changes must be made, if any, in

order that the machine operate satisfactorily as generator. If the speed is

driven above synchronism by the same revolutions per minute that the

machine normally operates at below synchronism, the generator will deliver

approximately rated current at rated voltage and rated efficiency. The electric

power out will be approximately equal to the rated shaft motor power. The

generator power factor will be much worse, being approximately equal to the

motor power factor times the motor efficiency.

I.5 Thesis Layout:

The aim of this dissertation project is to present a study of the potential sites

for hydropower development projects in Sudan with reference to induction

generator applications, taking Jebel Aulia Hydro-matrix project as an

example. To this end, Chapter II presents an over-view of the Hydro-matrix

experience with induction generators in Sudan. Chapter III shows the kind of

the experiments being done on the University of Khartoum Laboratory and

the equipments procured for that work and it is followed in Chapter IV by the

results of an investigation into the characteristics of grid-connected induction

2 From a paper written by OTTO J. M. SMITH with the title (Generator Rating of Induction Motors)magazine AIEE magazine, volume69, 1950.


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generators in terms of capability limits and power factors performance using

a suitably-matched experimental test bed. Verification results of steady-state

performance characteristics as well as experimental findings on the installed

hydro-matrix generators are also presented in this Chapter. Chapter V

presents the results of a research into the potential of additional sites for small

hydropower developments as well as the identification of large motor

installations for possible utilization as generators in Sudan.


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CHAPTER II

GRID-CONNECTED INDUCTION GENERATORS FOR SMALL HYDRO

WITH REFERENCE TO THE JEBEL AULIA EXAMPLE


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Chapter TwoGrid Connected Induction Generators for Small Hydro:

THE JEBELL AULIA EXAMPLE2.1 Technical Description:

The Hydro matrix power plant in Jebel Aulia consists of 80 turbine-generator

sets, which are installed in 40 modules by pairs as seen in figure (2.1)

Figure (2.1) view of three modules of the hydro matrix turbine


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Figure (2.2) view of one module (two turbines and generators)

Each module is equipped with two submerged, 380 kW horizontal propeller

turbines. Each turbine has a 1120 mm diameter, three-bladed runner

precision cast of aluminum bronze. Additionally, the scope of the VA Tech

Hydro contract contains all mechanical and electrical auxiliaries. NEC

carried out local activities for the accomplishment of the contract since Hydro

matrix makes use of the existing dam structure, only very minor civil

construction is needed. This is one of the predominant advantages of the

technology. The Hydro matrix modules are shipped to the Jebel Aulia dam

where they are installed into the existing water passage

the on/off operation of the turbines will be accomplished by means of the


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existing control gate. Both turbines of one module will be turned on or shut off

simultaneously. The gate has only an open and closed position.

Ten of the 690 V asynchronous generators feed into one common container

type generator switchgear substation. This arrangement is one out of eight

lots. Each one of these substations has its own control and step up transformer

and also includes the reactive power compensation.

A total of eight of these substations are installed at the dam side, on the

opposite side of the machines and handle the total plant output of the 80 units.

From these eight substations, individual 33 kv cables run to a 33 kv stationlocated beside the river. The whole power plant is managed from a central

plant control station. With this concept it is possible to operate each lot

independently from the others. The power station is connected to the national

grid through two 33 kv feeders feeding the Jebel Aulia substation by two

breakers named Z705 and Z805 as shown below in fig. (2-3)


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220KV220 KV

110KV110KV

33KV33KV

Z705Z805GitainaJebel

Jebel Auila power station Bus bar

SUNDUS

33KV

33K

V

Jebel

Gitaina

Fig (2.3) Connection to the National Grid


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Fig. (2.4) another view of the feeders seen on the PLC display with Z705 and Z

805


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Fig (2.5) Single-Line Diagram of Jebel Aulia S/S


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For emergency power supply a diesel generator unit is installed and acts as a

backup power supply in case of loss of net voltage for the control gates gear

motors and the module crane.

The induction generators as seen on (Figure 2.6) below

Fig (2.6) Connection Layout of the two generators (courtesy of VA TECH

HYDRO)


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Fig.(2.7) View of one turbo generator

2.2 Reasons for the Induction Generator Alternative:

The induction generator has been selected for the project due to the following

reasons:

1-No need to excitation system of direct current for the voltage and reactive

power control such as that used for synchronous generators.

2-No need to electro hydraulic governor to control the speed or the generator

frequency or any kind of speed droop as that used for synchronous machines.


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3-The induction generators are self-protected during surges and system

disturbances and have a very low fault current.

4- The motors (induction generators) are robust and reliable with low cost

and maintenance and high efficiency (squirrel cage type).

5- No synchronization problems of voltage, frequency and phase angle, what is

really needed ,is to have both the turbine and the generator to run at the same

direction with speed above the synchronous speed of the motor (375rpm ) and

the turbine is run with 379 rpm and then being connected to the system.

6-The compensation of the reactive power being absorbed by the induction

generators is done by means of shunt capacitors connected in steps manually

or automatically.

7-The operation and control of the hydro matrix turbines is simple and

reliable and constitutes a good and simple example of renewable energy

without pollution and complication if we consider the example of Egypt in

wind turbines at the Zafarana wind turbine fields which is used to produce

power with induction generators together with Photo Voltaic (PV) system

which is a very complicated system of inversion and power electronics (see

fig2.9).

8-The system is monitored and operated and controlled by means of a

Programmable Logic Controller (PLC) from Siemens Company (Somatic S7-

300) and is configured by the National Load Dispatch Centre (NLDC) SCADA

system by means of two servers according to the international relevant

standards and that kind of automation is very suitable for such a system as

shown below:


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Fig (2.8) General arrangement of Somatic S7-300 PLC

9 - There is a standby diesel engine generator to supply the low voltage system

and the batteries and close the gates in the case of power failure.

10-The induction generator is equipped by three sensors (pt100) formeasuring the temperature of the stator winding and giving alarm in case of

high temperature and two sensors for the temperature of the bearings (DE

&NDE) and three water level sensors to protect the generator from water

coming inside the generator and also there is one magnetic pick up speed

sensor.

2.3 System Protection:

A-Differential protection.

B-Voltage monitoring (over-voltage 1&2 and undervoltage 1&2).

C-Over-frequency 1&2 and under frequency 1&2.


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D- Over d current protection.

E-Earth-fault protection.

F-Over-load protection.

G-Reverse-power protection.

H-Over-speed protection.

I- Monitoring of stator windings temperature and bearings.

J- Leakage water level.


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NN=Neural Network.

PV=Photo Voltaic cells.

EU=Electric Utility.

Fig (2.9) Zafarana Wind field schematic diagram with photo voltaic cells in

Egypt


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Fig (2.10) the electric drawing of one module


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Fig (2.11) compensating circuit in 5 steps

2.4 Power Station Performance:

The power station is considered to be a very good example of efficient

electrical energy, where it is friendly to the environmental surroundings with

a very low cost and good price of MWHR (46.7 Sudanese pound), please refer

to appendix (B ) although it is totally shut down for four months as the head

goes below the required designed head (less than 1.88 m ) ,in spite of that

outage the performance has been found in good situation and somemodifications have been done to make better performance such as :

A- The total harmonic distortion (THD)of both voltage and current were

found very high at the beginning of the power station start due to the


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capacitor banks which are used for the power factor correction and

reduction of the reactive load burden of NEC (i.e. THD is above 50 % )

and that happened during the switching operation of capacitor banks

which are selected in five steps to raise the power factor from 66% up to

98%,and that high distortion obliged NEC to ask the help and advices of

their consultant Dr. Abdelrahman Karrar,who is the NEC technical

consultant and advisor, to study that problem where he stated that the

harmonics are not from the generator winding design which is well

designed and it is coming from NEC power system and the capacitors

which are nonlinear load. The problem was solved by VA TECH through

the insertion of passive filters (inductance) being connected in series with

the capacitor banks and it was almost vanished and the harmonics are no

longer

seen,

please see

figure

(2.12)


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Fig (2.12) Shunt capacitors connected in series with the inductance to remove

the harmonics (courtesy of VA TECH HYDRO).

B- Since all the generators are submersible and have got no heaters to prevent

condensation ,some water leakage are trapped inside the generators and the

water is detected by some sensors and cause tripping of the generator and it

was solved by means of drain pipes and small pumps, but it sometimes it

causes condensation and weak insulation of the stator windings, and that

problem was solved later by means of vacuum pump and heating system and

further on, a new modification of heating system through the generator

winding is proposed by NEC and Andritz Hydro will be going to implement

it as shown on the diagram below which is a proposal of heating the module


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With the use of direct current (DC) supply.

C- Some contactors of both the generator and the compensating circuit are

subject to failure and damage and burning from time to time during the

system disturbance and that was solved by new modification of the sequence

order of the system tripping by tripping of the capacitor bank at the first time

and keep the generator contactor closed, however, on real fault the contactor


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shall be tripped in normal condition and hence protecting the generator from

over voltage which is the most dangerous situation.

D- Connection of the power station with the main National load Dispatch

Centre (NLDC) through the SCADA system and Siemens PLC automation for

better communication.( only one channel is used and the other one could not

be operated).

E-The reactive power of the induction generators at the beginning of the

scheme is fed from the (Majarous) substation, through feeders of 33 KV, as

the substation is supplied with 110 KV and now it is fed from Jebel Aulia

substation which is supplied with 220 KV, where the problem of the voltage

drop is solved.

F- The power cable of the hydro matrix generator is not a submersible one

and sometimes it is subject to some damages and cut on the cable which leads

to weak insulation of the whole system (the cable +induction generator) that

problem is treated and solved by means of using a special kind of shrinkable

heating to seal the cable not to allow water to go inside the live conductors.

G-Runner Chamber and Draft Tube Problems:

Some cracks and cavities appear in the runner chamber and the draft tube

and many discussions with VA-TECH and the mechanical engineers of the

power station were made and finally they came to a solution of using the

coating devices which have the name (IRATHANE 155) and previously with

(CRAME-KOT) and the company agreed to turn out the existing mild steel

plates and install new stainless steel sleeves as already being fixed for the

runner chambers as reliable and durable solution and by making new plates

of stainless steel being welded above the original one.

Finally we hope that our company, the Sudanese Hydro Power Generation

Company Ltd (SHGC) with coordination of the ministry of dams and


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electricity could consider more projects and schemes similar to Jebel Aulia to

be implemented, like Sennar dam deep sluice gates and the Jazeera, Managil

canals and Elrahad canals as some studies which are included within this

thesis are done on this matter by the former NEC and the ministry of

irrigation (MOI) and the Jazeera scheme board. The Andritz Hydro company

has manufactured another design of hydro matrix with new system called

Straflo matrix which is mainly a hydro matrix turbine, but with a

synchronous generator that has a permanent magnet installed on the rotor of

the generator, although, there will be no need to compensating capacitors but

a further study and comprehensive load flow shall be done to select the best

design of the permanent magnet and our company has to decide which option

to select.


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CHAPTER III

EQUIPMENT PROCURED FOR LABORATORY INDUCTION

GENERATOR TESTS


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Chapter Three

Equipment Procured for Laboratory Induction Generator Tests

3.1 General:

This Chapter describes the set of experiments conducted at the Electrical

Machines Laboratory of the University of Khartoum aiming at investigating

the steady-state performance characteristics of grid-connected induction

generators. The equipment for these tests were obtained with considerable

effort as the available laboratory test beds of motor-generator sets were

thought unsuitable in terms of prime-mover power /generator ratios. Two

different motor-generator sets of higher ratios were procured with the help of

a NEC donation of a DC prime-mover motor and the technical assistance

received with respect to mechanical couplings. Digital multi-meters and power

quality analyzers were also made available for the active and reactive power

recordings under different operating conditions, including those of the

capacitor-compensated system aiming at power-factor improvements.

Calculations results of power-factor correction capacitors ratings based on

recommended practice tables are presented in this chapter.


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3.2 Induction Generator Test Equipment:

Fig (3.1) 5.5KW DC motor-2.0 hp Induction Motor Generator Set


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Fig (3.2) 5.5 KW DC motor-1.0 hp Induction Motor Generator Set


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Fig (3.3) Power-factor Correction Capacitor Bank of 18 F units


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Fig (3.4) Rheostats of different sizes for dc motor speed control


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Fig.(3.5)the speed indicator of the 2 hp motor in r.pm.

Fig (3.6) A View of the power quality analyzer (Fluke 434)


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The equipment acquired for the experiment consists of M-G sets, resistor and

capacitor banks assemblies and measuring/recording instruments. These are

shown in Figures (3.1 up to 3.6) where the corresponding specifications are

given in Appendix (D).The acquisition of the M-G sets shown in Figures (3.1

and 3.2) was in particular a hard and time-consuming task. In this respect, the

donation by NEC of the DC motor drive and the technical assistance received

with the alignment and coupling of the two experimental motors is greatly

acknowledged.

Since the prime mover is designed to run with a speed of 2900 rpm it is only

possible to decrease the speed by armature control and we are able to do that.

Many shots of operations were made for running the induction motor as a

generator and could be seen on the results obtained and the application of

capacitor banks (Figure 3.3) (shunt type) for both connection of star and delta

and by the use of the compensation table which is attached to appendix (C)

and even the attempts of connection of the series capacitor as explained.

It is worth mentioning that during the tests of the series capacitors an accident

happened which caused a complete failure of the coupling associated with a

very high noise and after investigation and inspection it was found coming

from the utility supply which was received at that time in a reverse direction

and that was a mal operation by (NEC) operation and distribution staff after

a maintenance work. That failure caused us too much time to find another

motor and to make new coupling at the industrial area of Khartoum North.


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Finally we get a new induction motor (squirrel cage) with a power of one hp.

and being driven by the same 5.5 KW dc motor the schematic diagrams of

both the dc motor and the induction motor can be seen on figure (3.6)

Fig.(3.6) DC-Motor Prime-mover Arrangement for Induction Generator

Experiments.As it is explained previously all our tests and experiments are done with that

kind of grid connected generators, where the reactive power needed for the

magnetization is obtained from the grid and due to the non-availability of

Induction motor schematic diagram

5.5 kw dc motor coupled with the induction motor


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some devices and equipments such as the dynamometer or the LABVIEW

equipments with its software and we started looking for dc source capable of

running the 5.5 kw dc motor but we could not find it in Khartoum, some

tests are simulated by MATLAB program such as series capacitor and speed

torque curve and reactive power curve and the power factor to slip curve as

can be seen on the results chapter

3.3 Measurement of Induction Motor Parameters:

The 2 hp induction motor parameters which are xs,xr,rs,rr,xm and rc were

measured by means of the following tests:

1-The DC test for stator resistance by means of battery voltage of 12 v dc and

a limiting resistor of 8 ohm as shown below

Fig (3.7) stator winding resistance measurements2-No load test

3-Locked rotor test

The stator winding resistance was obtained by means of a dc source from a

car battery which was equivalent to 12.87 v dc and a limiting resistor of 8 ohm

and by taking three readings as shown below


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1-2rs=2.56 v/1.121A = 2.384 ohm

2-2rs=2.59 v/1.124A = 2.304 ohm

3-2rs=2.59 v/1.126 A= 2.300 ohm

The average value of rs is (2.384+2.304+2.300)/6 = 1.165 ohm. And by the

display of the fluke meter which is shown below seen on figure (3.8).

Fig.(3.8) no-load test display data of the 2 hp motor

DPF=Distortion Power factor


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Fig.(3.9) locked-rotor test display of the 2 hp motor

And the table (3-1) is showing the measured values of the No load test and the

locked rotor test which was done by supply voltage of 50 Hz in frequency and

reduced voltage as shown below:

Table (3-1) results of the no load test and blocked rotor test

S

Speed

in

rad/sQPVavIcIbIaType of test

0.63

KVA

157.08

rad/s0.57 KVAR0.26

KW231.3 V1.5

A1.7 A1.5 ANo load test

0.96

KVA0

Rad/s0.85 KVAR0.45

KW77.16 V7.1

A7.2 A7.3 ABlocked

rotor test


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It is worth mentioning that the locked rotor test is done by means of variable

transformer of 1500 VA.

Fig (3.10) equivalent circuit of No load testAlso the figure below shows the locked rotor equivalent circuit

Fig(3.11) equivalent circuit of locked rotor

From the figures shown above the following calculations are done for the

parameters measurement

From the No load test the following equation can be used

(3.1)

Average value of IO is (1.7+1.5+1.5)/3=1.566 A

Znl =(0.57/ (1.5666)2)*1000 /3 = 77.48 ohm

The above mentioned value is equivalent to X1 +XM


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The stator copper loss is equal to

PSCL =3IO2R =3*1.5666*1.566*1.165 = 8.57 w (3.2)

Therefore the no load rotational losses are

Prot =PinPSCL =260 -8.57=251.43 watts

From this value we can find out the Rc resistance which is equivalent to:

Rc = (Vph)2/Prot/3 = 17834.3/251.43/3 =212.8 ohm (3.3)

From the locked rotor test,

Iav= (7.3+7.2+7.1)/3 =7.2 A (3.4)

The locked rotor reactance is XLR= (Q/3)/I2

(3.5)

= (850/3)/51.84

=5.465 ohm

From the rules of thumb which is dividing the stator and rotor reactances as

it is made over years of experience since there no simple way to separate the

contributions of the stator and rotor reactances from each other.

The table below is showing the relation between stator and rotor reactance


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Table (3.2) Rules of thumb dividing rotor and stator reactance

X1 and X2 as a function of XLRRotor DesignX2X1

0.5 XLR0.5 XLRWound rotor0.5 XLR0.5 XLRDesign A0.6 XLR0.4 XLRDesign B0.7 XLR0.3 XLRDesign C0.5 XLR0.5 XLRDesign D

So the values of XLRis equal to(X1+ X2) since our rotor is wound type

X1 = X2 =5.465/2 = 2.732 ohm (3.6)

The locked rotor resistance, RLR=R1 +R2 (3.7)

So the RLR= (P/3)/Iav2= (450/3)/ (7.2 *7.2) (3.8)

= 2.89 ohm

Then R2 is equal to 2.89-1.165 = 1.723 ohm

Also we can find the value of XM which is equal to 77.48-2.732

=74.74 ohmSo now we can arrange all the motor parameters as follows:


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1- x1 = 2.732 ohm

2- x2/= 2.732 ohm

3- r1 = 1.165 ohm

4- r2/= 1.723 ohm

5- Synchronous speed =1500 rpm

6- motor voltage line to line =230 v

7- XM = 74.74 ohm

8- Frequency =50 Hz9 - Rc =212.8 ohm


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Fig.(4.2) Generated Power Display= 1.8 KW

Fig.(4.3) 2hp motor data display as generator


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Fig(4.4)the 2hp motor as a generator with capacitor banks

For the measurement of the 2hp motor parameters the following displays

were obtained:

The MATLAB displays of the 2hp motors were shown below after obtaining

the motor parameters on the previous chapter (chapter 3 and Appendix E)


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Fig.(4.6) torque /speed curve of the 2hp motor

Fig.(4.7) reactive power/speed curve of the 2 hp motor


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Fig.(4.8) power factor/speed curve of the 2 hp motor

Fig.(4.9) efficiency /speed curve of the 2 hp motor

0 500 1000 1500 2000 2500 30000

100

200

300

400

500

600

700

800Induction Motor

Efficiency(%)

Speed (RPM)

30

40

50

60

70

80

90

100


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Fig(4.10) the 2 hp motor with capacitors in series

Fig.(4.11) the 2 hp motor with capacitors in series


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And there were some other displays shown below:

Fig.(4.12) the harmonic contents of the 2 hp motor

Fig.(4.13)the red phase current harmonic content


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Fig.(4.14) the yellow phase current harmonics content

Fig.(4.15) the blue phase current harmonics content

4.2 Power-factor Calculations Procedure:Table-based:

The power factor calculations were based on the table shown below:


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Table (4.1) the required KVAR of the capacitor for power factor correction


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The 2hp motor power factor calculation was done as follows:Although the induction motor rated power was only 2 hp which was

approximately equal to 1.5kw, and by driving the generator by the dc motor it

was noticed that the generator was very stable and no more heat could be

observed, but it was noticed that the rheostats which were rated by 16 ampere

and used to control the dc motor speed became very hot and the current was

almost equal to 25 A. Then it was seen that the power factor was equal to 0.84

with a reactive power of 1.2 kvar and by the power factor correction table

On the view of power factor correction table

It became possible to use it and do the following calculation

P (tan 1-tan2) = Q (4-1)

Where P is rated power of the induction motor, and 1 is the power factor

angle before the improvement and 2 is the power factor angle after the

correction, and Q is the reactive power needed for the correction in (VAR).

The rating of the capacitors can be obtained by the following formula

Qn =Un.In (4-2)

Where Unis root mean square (rms) value of the ac voltage applied.

In is the rms of the capacitor current.

Qn =Un.Un/Xn (4-3)

Where Xn is the capacitive impedance and equal to

Xn=1/wCn=1/2fCn ... (4-4)


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Where f =fundamental frequency in Hz

Cn =total capacitance in farad

Calculation of the compensated reactive power in (vars) from 0.85 powerfactor to 0.98 power factor.

1500(0.417) = 625.5 vars

Cn =Qn/ (Un2*2*f) which is used for star () connected capacitor

And when it is used for delta () the equation is

Cn =Qn/ 3(Un2*2*f).. (4-5)

So the capacitor value is equal to

Cn() =625.5/ (220*22o*2**50) = 41.136 F

This capacitor is connected in parallel to the induction generator and the

improvement received is shown on figure (4.4) where a power factor equal to

0.98 was got.

4.3Calculations and Measurements for the Jebel Aulia Hydro -matrix Units

Tests:

The following calculations were made to find out the induction motor

parameters and it was based on the factory tests which were done on the

factory and it was as follows:

The parameters of the induction generators of Jebel Aulia

The following results are obtained from the factory tests of the induction

generators in Austria.


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Now we can find the average value of the stator winding resistance

Rs= (0.007910+0.007932+0.007955)/3 =0.007932 ohm

From the no load test we can find

Zeq. = (V/3)/I. (4-6)

=2.9995 /3 with angle 88.11

=1.7317 sin 88.11

= 1.7308 ohm

=Xs +XM

The stator copper losses

PSCL=3I2Rs. (4-7)

= 3(230.04)2(0, 007932)

=1.256 KW

Im = Iosin. (4-8)


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=230.04 sin 88.11 = 229.91 A

Ic= Iocos (4-9)

=230.04 cos 88.11

Rc =Vph/Ic (4-10)

=398.371/7.586

=52.63 ohm

Locked Rotor Test

Zsc =Vph/I (4-11)

= (207.7/3)/460

=119.915/460

=0.2606 ohm

=0.2606 cos

=0.2606x0.174

=0.0453 ohm =Rs +Rr

Rr =0.0453-0.007932

=0.03742 ohm

Xeq = Zscsinsc (4-12)

= 0.2606 sin 79.97

=0.2566 ohm


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Xeq = Xr +Xs..... (4-13)

Xr = Xs

= 0.2566/2

= 0.1283 ohm

XM= 1.73080.1283

= 1.6025 ohm

Now we can arrange all the induction motor parameters as follows

Vs = 690 v line to line

=398.371 v phase to ground

Induction generator speed =379 rpm, which is obtained by the turbine and

above the synchronous speed.

Please note that the synchronous speed is equal to 375 rpm with total number

of 16 poles

XM =1.6025 ohm.

XS = 0.1283 ohm.

Xr/

= 0.1283 ohm.

rs =0.007932 ohm.

rr/

= 0.03742 ohm.

RC = 52.63 ohm.

We also made different displays at the power station and we got the following


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Displays:

Fig.(4.16) Harmonics content of all three phase currents

Fig.(4.17) Wave of the three phase currents


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Fig (4.18)Wave of the three phase voltage

Fig.(4.19)Power and Energy of the induction generator of JebelAulia


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Fig.(4.20) Harmonic contents of the currents

Fig.(4.21) Volt/Amp/hertz of the induction generator of Jebel Aulia


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Fig.(4.22) Display of the current waveform

Fig.(4.23) Display of the voltage waveform

Fig.(4.24) Power and Energy of the induction generator


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Fig.(4.25) Another display of power and energy of the induction

generator

Fig.(4.26) Harmonic table for the three phase currentsAnd from the parameters obtained and by using MATLAB system the

following displays were obtained for Jebel Aulia induction generators:


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Fig.(4.27) Active power/speed curve

Fig.(4.28) Reactive power/speed curve

0 100 200 300 400 500 600 700 800-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1x 10

6 Induction Motor

ActivePower(Watts)

Speed (RPM)


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Fig.(4.29) Power factor/speed curve of the jabal motor

Fig.(4.30) Torque /speed curve of Jebel IG


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Fig.(4.31) Simulation of capacitors connected in series

Fig.(4.32) Simulation of capacitors connected in series


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CHAPTER V

RECOMMENDED SITES OF SMALL POWER GENERATION IN SUDAN


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Chapter Five

Recommended Sites of Small Power Generation in Sudan

5.1 Utilization of Induction Motors and old Synchronous Generators:

It is noticed that most of the highly industrial countries are making their best

to get use of their old replaced electric machines whether they are

synchronous or asynchronous. As an example to that on the Unites State of

America (USA) they have what is called (VAR pumping stations) which means

that their old synchronous machines are best utilized and being used as

synchronous condensers (production of reactive power) after the removal of

their old prime movers which are now replaced by new modern electric drives

or by closing the guide vanes by means of compressed air system in case of

hydro power generators. Also the induction motors can be made to operate as

induction generators since induction generators control is very simple and

need neither speed governor nor excitation system control.

If we look at the situation of our country (Sudan) we can say that we have lost

all of our old electric machines whether they are synchronous or

asynchronous. When considering the history of the electric generation in

Sudan and the industrial development of factories, we can start with different

old power stations and they are described as follows:


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5.1.1Kilo-X gas turbine power station:

That power station which was used in the past for production of power and

being used for voltage control as it was made operated as a synchronous

condenser by means of an electric clutch which was used to disconnect the

prime mover from the generator after the synchronization process and was

left working alone with a few kilowatts to compensate the losses and by means

of its Automatic Voltage Regulator (AVR), the reactive power was controlled

very smoothly without any problem. One can consider the loss we had got and

faced referring to its generator which had got an apparent power of 18.8

MVA and a power of 15 MW if we could understand the difficulty of getting

the spare parts of the gas turbine for its operation and sustainability. The

NEC administration had decided as a consequence matter of the parts non

availability to make the generator as a synchronous condenser by means of

electric drive and NEC tried its best to place tenders so as to do that

particular job, but in vain since as we discovered later that NEC was not

willing to do that work as it was considered as a matter of high cost and that

was on the year 2003 and the whole power station was put out of service and

all its equipments were sold as scarabs and a good opportunity was lost for a

device that could help on the national grid stability and contribute a good

training tool for students of engineering colleges in Sudan.

5.1.2Burri II Power Station:That was the first power station on Sudan and it consisted of different types

of power plant units such as steam and diesel. As the power station was old

and the difficulty of obtaining the spare parts and the original manufacturer's


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generators and that had not been used at the time of power shortage. And

almost most of them were treated similar to NEC policy.

Utilization of old electric machines gets its importance from the comparison

of the new static VAR compensating devices such as capacitors which are

controlled by means of power electronic devices and their bad adverse of

harmonics generation, whereas the old machines could produce a clean

reactive power without any distortion and contribute actively to the steady

state stability of the system.

5.2Potential for Small Hydro Power Schemes:

With reference to the high success of Jebel Aulia Hydro matrix project in

Sudan as a unique scheme in Africa and aiming at best utilization of existing

dams and canals for the production of electric energy with the minimum of

new civil work or additional cost and damage to the environment, experts

from ministry of irrigation ,the Jazeera Scheme board, Elrahad agricultural

project and the previous national electricity corporation NEC decided tomake a feasibility study to study the existing dams and canals for both

Elrahad and Jazeera and Managil schemes.

It is worth mentioning that the expert team was established in the year 2004

with the following engineers:

1- Dr. Ahmed Salih Hussien.. Hydraulic Research Station

Manager (MOI)

2- Eng.Elkarori Elhaj Hamad Dams Directorate Manager

(MOI)

3- Eng. Adam Abbaker .Project Directorate Manager (MOI)


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4- Eng.Elzain Abdelrahim..Agricultural Projects Manager (MOI)

5- Eng.Mohamed Oro Salim.. Hydro Power Manager (NEC)

6- Eng.Mudawi Abdelkarim Musa..Hydro Matrix Project Manager

(NEC)

7- Eng.Dafalla ElkabashiEngineering Directorate Manager

(Jazeera Scheme Board)

The expert team started this study from Sennar dam where a similar matrix

turbines of Jebel Aulia could be erected as the dam itself can be divided into

three parts:

1- There are 80 deep sluice gates

2-The gates of Jazeera and Managil canals

3-Downstream canals such as kilo 57and kilo 77

All these parts can be treated similar to Jebel Aulia Hydro matrix turbines

and the estimated powers that would be produced are tabulated as in Data

from Aljazeera, Managil and Elrahad projects shown below.


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Fig (5.1) downstream view of Sennar Dam

Fig (5.2) another view of Sennar dam


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Fig (5.3) Kilo 0 of Sennar dam

Fig (5.4) Kilo 77 of Jazeera Canal


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Fig (5.5) Kilo 57 bridge of Jazeera Canals


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The data obtained from Elmanagil is shown below on this table

Table (5.1) data from Elmanagil project

It starts from Sennar dam.

It goes in the north direction parallel to Elmanagil canal until kilo 57.

After kilo 57 they are separated and the Jazeera canal continuing to the

north.


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Table (5.2) Data from Al jazeera project

STATION GATES(NUM,DIA)MAX.HEAD(M) Max.Discharge In

M3/seconds

ESTIMATED

POWER(MW)

Connection to the

grid

Citiesand

villages

kilo0 from

Sennardam

N=14,5*3M,MANU

AL6.5 218.8 8.5 11 KV Sennar

kilo 77N=4(2P),3*3.75M,M

ANUAL 2.3 150.5 2.1 11KV5villages

kilo 57N=6(2P),3*3.75M,MANUAL

2.5 162.1 2.4 11KV4villages

Beka kilo

108

N=3,3.5*6M,MANU

AL2.3 92.6 1.3 11KV

Many

villages


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Fig (5.10) View No 2 of AbuRakham dam


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Fig (5.11) Kilo 22 Bridge on Rahad canal


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Fig (5.13) View no.2 of kilo 36 bridge


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CHAPTER VI

CONCLUSIONS AND RECOMMENDATIONS


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CHAPTER VI

CONCLUSIONS AND RECOMMENDATIONS

6.1 General

It can be shown that from the views shown below that India is very

famous in this field and has got an excellent experience on the small

hydro power schemes and our country can benefit from it with mutual

cooperation between Sudan and India.

Fig (6.1) typical arrangement of canal fall small hydro power station


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Fig (6.2) typical arrangement of small hydro power station

Fig. (6.3) another typical arrangement of small hydro power plant


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Fig (6.4) Kalmoni 200 kW SHP project near Guwahati in Assam

6.2The advantages of the experience:

The main advantage in this experience is that they succeeded to generate

hydroelectric power using the small quantity of water and low head.

And the disadvantages when considering the power obtained by means

of synchronous generators is that:


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1-They use the conventional type of turbines and this needs more civil

work in the existing dams.

2-The diversion canal increases the civil work.3-The conventional type using of governor system and excitation system

so it increase the capital cost.4-As general it is noticed that the new civil work makes a high cost.

5-Synchronization of small synchronous generators to the grid is very

difficult and risky since the load sharing will not be proper (KW)

between the machines and the grid and the reactive power sharing is

also very difficult (KVAR) and might lead to failure of the small

synchronous generators.

But when we consider the induction generators we can see that the

advantages of the induction generator were: simplicity of control

apparatus, freedom from hunting, no exciter required, no synchronizing

required, low fault currents, low cost, and subsequent general

usefulness in later motor applications and that it is the most suitable

electric machines for such an application.

We are looking forward at future to get use of all our water resources in

our new projects and existing ones and even for the seasonal streams

and canals in all Sudan.


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References:

1-Power Engineering International magazine, June 2004.

2-Jebel Aulia hydro matrix power station documents

3-International Energy agent Report (Key issues in developing Renewable

1997)

4-http://grz.g.andritz.com/c/com2011/00/01/24/12429/1/1/2/345644646/hy-

hydromatrix-en.pdf

5-Presentation of small hydro power station done by the joint committee of

NEC and MOI and Jazeera Board.

(http://www.4shared.com/document/bwv2Mzhl/small_hydro.html)

6-Indian experience with small hydro power station

(http://www.mnre.gov.in/prog-smallhydro.htm)

7- from a paper written by OTTO J. M. SMITH with the title (Generator

Rating of Induction Motors) magazine AIEE magazine, volume69, 1950

8-Electric Machinery Fundamentals. By Stephen J.Chapman
http://www.mnre.gov.in/prog-smallhydro.htmhttp://www.mnre.gov.in/prog-smallhydro.htmhttp://www.mnre.gov.in/prog-smallhydro.htm


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APPENDIX A3

Theory of Poly- phase Induction Machines

The analysis begins with the development of single-phase equivalent circuits.The general form is suggested by the similarity of an induction machine to a

transformer.

The equivalent circuits can be used to study the electromechanical

characteristics of an induction machine as well as the loading presented by the

machine on its supply source.

1. Introduction to Poly phase Induction Machines

An induction machine is one in which alternating current is supplied to the

stator directly and to the rotor by induction or transformer action from the

stator.

The stator winding is excited from a balanced poly phase source and produces

a magnetic field in the air gap rotating at synchronous speed.

The rotor winding may one of two types.

A wound rotor is built with a poly phase winding similar to, and wound with

the same number of poles as, the stator. The rotor terminals are available

external to the motor.

A squirrel-cage rotor has a winding consisting of conductor bars embedded in

slots in the rotor iron and short-circuited at each end buy conducting end

rings. It is the most commonly used type of motor in sizes ranging from

fractional horsepower on up.

The difference between synchronous speed and the rotor speed is commonly

referred to as the slip of the rotor. The fractional slip s is

3Appendix Reference: Electric al Machinery and transformer_ Bhag S.G


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s

s

n ns

n

(a .1)

The slip is often expressed in percent.

n : Rotor speed in rpm

s

nsn 1(a .2)

m : Mechanical angular velocity

sm s 1(a .3)

rf : The frequency of induced voltages, the slip frequency

r ef s f(a .4)

A wound-rotor induction machine can be used as a frequency changer.

The rotor currents produce an air-gap flux wave that rotates at synchronous

speed and in synchronism with that produced by the stator currents.

With the rotor revolving in the same direction of rotation as the stator field,

the rotor currents produce a rotating flux wave rotating at ssn with respect to

the rotor in the forward direction.

With respect to the stator, the speed of the flux wave produced by the rotor

currents (with frequency esf ) equals

s s s s1sn n sn n s n (a .5)

Because the stator and rotor fields each rotate synchronously, they are

stationary with respect to each other and produce a steady torque, thusmaintaining rotation of the rotor. Such torque is called an asynchronous

torque.

(a .6)The torque equation2

sr r r

polessin

2 2T F


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can be expressed in the form

r rsinT KI (a .7)

rI: The rotor current

r: The angle by which the rotor mmf wave leads the resultant air-gap mmf

wave

Fig.( a.4) shows a typical poly phase squirrel-cage induction motor torque-

speed curve. The factors influencing the shape of this curve can be

appreciated in terms of the torque

equation.

Figure (a .4) typical induction-motor torque-speeds

Curve for constant-voltage, constant-frequency operation.

Under normal running conditions the slip is small: 2 to 10 percent at full load.

The maximum torque is referred to as the breakdown torque.

The slip at which the peak torque occurs is proportional to the rotor

resistance.

2. Currents and Fluxes in Poly phase Induction Machines


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2.3 Induction-Motor Equivalent Circuit

Only machines with symmetric poly phase windings exited by balanced poly

phase voltages are considered. It is helpful to think of three-phase machines

as being Y-connected.

Stator equivalent circuit:

11121 jXRIEV (a .8)

1

2

1

1

1

Stator line-to-neutral terminal voltage

Counter emf (line-to-neutral) generated by the resultant air-gap flux

Stator current

Stator effective resistance

Stator leakage reactance

V

E

I

R

X

Figure (a.7) Stator equivalent circuits for a poly phase induction motor.

Rotor equivalent circuit:

2

22

I

EZ (a.9)

2 22s rotor 2s eff eff rotor

2s rotor

E EZ N N Z

I I

(a.10)

2sZ: the slip-frequency leakage impedance of the equivalent rotor


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E

rotorZ: the slip-frequency leakage impedance

2s2s 2 2

2s

EZ R jsX

I (a.11)

2R= Referred rotor resistance

2sR= Referred rotor leakage reactance at slip frequency

2X= Referred rotor leakage reactance at stator frequency

ef

Figure (a.8) Rotor equivalent circuits for a poly phase induction motor at slip

frequency.

22 II s (a.12)

22 sEE s (a.13)

22

EsEs

(a.14)

222

2

2

2

2

jsXRZI

Es

I

Es

s

s (a.15)


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s

sRInP

12

2

2phmech(a.21)

gapmech 1 PsP (a.22)

rotor gapP sP(a.23)

Of the total power delivered across the air gap to the rotor, the fraction 1 s is

converted to mechanical power and the fraction s is dissipated as ohmic loss

in the rotor conductors.

When power aspects are to be emphasized, the equivalent circuit can be

redrawn in the manner of Fig. 6.10.

Figure a.10 Alternative form of equivalent circuit.

Consider the electromechanical torque mechT .

mechmechmech 1 TsTP sm (a.24)

s

sRInPP

T

/22

2ph

s

gap

m

mech

mech

(a.25)

ee

s

f

poles

2

poles

4(a.26)

rotmechshaft PPP (a.27)


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Figure a.13 Induction-motor equivalent circuits simplified by Thevenins

theorem.

m

m

XXjR

jXVV

11

1eq1,(a.29)

1,eq 1,eq 1,eq 1 1 in parallel with mZ R jX R jX jX (a.30)

m

m

XXjR

jXRXjVZ

11

111eq1,

(a.31)

sRjXZ

VI

/

22eq1,

eq,1

2

(a.32)

2

2eq1,

2

2eq1,

2

2

eq1,ph

mech/

/1

XXsRR

sRVnT

s(a.33)

The general shape of the torque-speed or torque-slip curve with motor

connected to a constant-voltage, constant-frequency source is shown in Figs.

a.14 and a.15.


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Figure a.14 Induction-machine torque-slip curve showing braking, motor, and

generator regions.


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K

Figure a.15 Computed torque, power, and current curves for the 7.5-kW

motor in Exps a.2 and a.3.

Maximum electromechanical torque will occur at a value of slipmaxTs for

which

2

221,eq 1,eq 2

maxT

RR X X

s (a.34)

2

maxT22

1,eq 1,eq 2

Rs

R X X

(a.35)

2

2eq1,

2

eq1,eq1,

2eq1,

max

5.01

XXRR

VnT

ph

s(a.36)

Figure a.16 Induction-motor torque-slip curves showing effect of changing

rotor-circuit resistance.

(a.5)Parameter Determination from No-Load and Blocked-Rotor Tests


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The equivalent-circuit parameters needed for computing the performance of a

poly-phase induction motor under load can be obtained from the results of a

no-load test, a blocked-rotor test, and measurement of the dc resistances of

the stator windings.

a.6.1 No-Load Test:

Like the open-circuit test on a transformer, the no-load test on an induction m

otor gives information with respect to exciting current and no-load losses.

a.6.2 Blocked-Rotor Test:

Like the short-circuit test on a transformer, the blocked-rotor test on an induc

tion motor give information with respect to the leakage impedances.


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APPENDIX B


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APPENDIX C

SIMPLE KW MULTIPLIER FOR POWER FACTOR CORRECTION

Known Variables: Capacitor Voltage and Capacitor Reactance

KVAR = (2fc)(kv)2

/1000

=(kv)2/1000xc

Known Variables: Capacitor Frequency, Capacitance, and Voltage Rating

KVAR = (2fc)(kv)2

/1000

=(kv)2/1000xc

Reference:

http://www.nepsi.com/powerfactor.htm


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APPENDIX D

All the tests and experiments have been done at the faculty of engineering

laboratory (electrical machines lab.)And the following devices and equipments

are used with the following specifications:

Ac induction motor

The motor has got a serial number of 5/15145/290/4/1 and size KKS 3

Power: 2 hp,Speed: 1430rpm, Phases : 3, Frequency: 50 Hz

Voltage:282 v,Current:4.7 Ampere Connection : star

CONT: RatingBs, Insulation class: E, Rotor: 115v current: 8.6 A

The motor is a wound type one where we make it similar to the squirrel cage

one by making short to the windings of the rotor through the slip ring and it is

possible to run it by direct supply of 220 v(three phase supply obtained from

delta side of the lab transformer.)

DC MOTOR

The DC motor is used as a prime mover with the following specifications:

Serial number: 1324-16180, Type: LAP 132-4M

Standard: IEC 34/1 -1969 and now it is IEC 60034/1, Speed: 2900 rpm

Duty: S1, Insulation class: F , Armature voltage: 240 v dc

Armature current: 25.8 A , Excitation voltage: 240 v dc

Excitation current: 0.595 A, IP : 54, IC: 0011 ,IM :1.001


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P

Weight: 145 Kg.

UCTION MOTORDTHE 1 HP IN

This motor is smaller in size and equivalent of one hp and can be operated byeither, 400 v or 230 v of 50 HZ by means of connection of either star or delta;

it has got the following specifications:

The motor name plate is SAER ELETTRO POMPE

Type: HT4-B3-80, Serial number: 1997522, HZ =50

Rated voltage: 240/400 (star/delta), Rated current: 3.6/2.1 A

Speed: 1470 rpm, Power in kW: 0.75, or 1 hp

APPARATUS

The following meters were used for most of the testing and measurements and

all of them were calibrated

a- Power Quality Analyzer (Fluke434)

b- AC/DC multi meter (Fluke 87)c- Clamp meter for ac current measurement


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% The parameters are R1, X1, X2, R2, Xm, Vt, Ns

% Assumed is a three-phase motor

% -----------------------------------------------------

--

Functionsc;

R1 =0.007932;

X1 = 0.1283;

R2 =0.03742;

X2 =0.1283;

Xm =1.6025;

Vt =398.37;

Ns =375;

s = -1:0.003:1; % vector of slip

N = Ns .* (1 - s); % Speed, in RPM

oms = 2*pi*Ns/60; % Synchronous speed in rad/secRr = R2 ./ s; % Rotor resistance

Zr = j*X2 + Rr; % Total rotor impedance

Za = j*Xm.*Zr./(j*Xm + Zr); % Air-gap impedance

Zt = R1 + j*X1 +Za; % Terminal impedance

Ia = Vt ./Zt; % Terminal Current

I2 = Ia .*j*Xm./(Zr + j*Xm); % Rotor Current

Pag = 3 .* abs(I2) .^2 .* Rr; % Air-Gap Power

Pm = Pag .* (1 - s); % Converted Power

Trq = Pag ./oms; % Developed Torque

plot(N, Trq);title('Induction Motor');

ylabel('Torque (N-m)');

xlabel('Speed (RPM)');

gridon;

% -----------------------------------------------------

-% Power Factor-Speed Curve for an Induction Motor

% The machine is 482,8-hp, 690-V, wye-connected, three-

phase, 50-Hz, 16-pole, 375 rpm

% The parameters (referred to the stator) are R1, X1,

X2, R2, Xm,


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oms = 2*pi*Ns/60; % Synchronous speed in rad/sec

Rr = R2 ./ s; % Rotor resistance





I2 = Ia .*j*Xm./(Zr + j*Xm); % Rotor Current

Pag = 3 .* abs(I2) .^2 .* Rr; % Air-Gap Power


Trq = Pag ./oms; % Developed Torque

plot(N, Trq);

title('Induction Motor');

ylabel('Torque (N-m)');xlabel('Speed (RPM)');

gridon;

% -----------------------------------------------------

-

% ActivePower-Speed Curve for an Induction Motor

% Assumes the classical model

% This is a single-circuit model

% The parameters are R1, X1, X2, R2, Xm, Vt, Ns% Assumed is a three-phase motor

% -----------------------------------------------------

--

functionapsc;

R1 =6.93;

X1 =2.63;

R2 =3.82;

X2 =2.63;

Xm =104.31;

Vt =230/sqrt(3);Ns =1500;



Rr = R2 ./ s; % Rotor resistance




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P =3.*real(Vt.*conj(Ia)); % Total injected active power

plot(N,P);


ylabel('Active Power (Watts)');


gridon;

%supply parameters

Vin = 230; %voltage

% f = 50 % frequency

% induction motor parameters

Rs = 0.403;

Xs = 0.740;

Rr = 0.511;

Xr = 0.740;

Xm = 12.258;

Ns = 1500;

W = 2*pi*Ns/60;

% 1st case when Slip is constant and Xc varies

% S = -0.02; %-ve slip Generator mode

% Zf = i * Xm * (i * Xr + Rr/S) / ( Rr/S + i * (Xm +

Xr));% Xc = 0:0.1:50 ;%variable series cap.

% Ztotal = Zf + Rs + i * (Xs - Xc);

% I = abs(Vin * Ztotal.^-1);

% ph = angle(Vin * Ztotal.^-1);

% subplot(2,1,1), plot(Xc,I)

% xlabel('Series Capacitance')

% ylabel('Current Amplitude')

% subplot(2,1,2), plot(Xc,ph)

% xlabel('Series Capacitance')

% ylabel('Current phase')Xc = 0.25; % Set here the best value of series cap.

impedance value

S = -1:0.002:1;%variable slip

S(501) = 0.001;% avoid division by zero

Zf = i * Xm * (i * (Xs-Xc)+Rs)/(Rs + i*(Xs+Xm-Xc));

Ztotal = Zf + Rs * S.^-1 + i * Xr;


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Vth = Vin * Xm/(Rs + i*(Xm +Xs - Xc));

Ir = abs(Vth * Ztotal .^-1);

T = 3* Rr*(Ir.^2 ./ S)/W ;

plot(S,T)

title('Induction motor Torque/Slip Curve')

xlabel('Slip')

ylabel('Torque')

%supply parameters

Vin = 230; %voltage

% f = 50 % frequency

% induction motor parameters

Rs = 0.403;

Xs = 0.740;

Rr = 0.511;

Xr = 0.740;

Xm = 12.258;

% 1st case when Slip is constant and Xc varies

S = -0.02; %-ve slip Generator mode

Zf = i * Xm * (i * Xr + Rr/S) / ( Rr/S + i * (Xm +

Xr));

Xc = 0:0.1:50 ;%variable series cap.

Ztotal = Zf + Rs + i * (Xs - Xc);

I = abs(Vin * Ztotal.^-1);ph = angle(Vin * Ztotal.^-1);

subplot(2,1,1), plot(Xc,I)

xlabel('Series Capacitance')

ylabel('Current Amplitude')

subplot(2,1,2), plot(Xc,ph)

xlabel('Series Capacitance')

ylabel('Current phase')

% 2nd case when Xc is constant and S varies

Xc = 0.5; % series cap. impedance value

S = -1:0.02:-0.001;%variable slipZfn = i * Xm * (i * Xr + Rr* S.^-1);

Zfd= Rr*S.^-1 + i * (Xm + Xr);

Zf = Zfn ./Zfd;

Ztotal = Zf + Rs + i * (Xs - Xc);

I = abs(Vin * Ztotal.^-1);

ph = angle(Vin * Ztotal.^-1);


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Pin = 3.*real(Vt.*conj(Ia)); % Total injected active

power

E = 100.*Pm./Pin; % Efficiency

plot(N,E);


ylabel('Efficiency (%)');


grid on;

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