final report

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MURDOCH UNIVERSITY

FACULTY OF SCIENCE AND ENGINEERING

SCHOOL OF ENGINEERING AND ENERGY

Engineering Internship Final ReportAn Internship with Fortescue Metals Group Limited

Prepared by Daniel Paino

On 4th

June 2012

For Dr. Gregory Crebbin and Dr. Gareth Lee

A final year report submitted to the School of Engineering and Energy, Murdoch University, in partial

fulfillment of the requirements for the degree of Bachelor of Engineering.


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Executive Summary

Over the period from August 2011 to May 2012, the intern was placed at Fortescue Metals

Group Limited in Perth Western Australia to carry out his final year engineering project, which

would fulfil the requirements of his degree studied at Murdoch University. The internship

placement was an accelerated learning experience which gave the intern the unique

opportunity to apply all his knowledge gained through studying the Bachelor of Engineering

degree.

The intern worked under the supervision of the Principal Electrical Engineer and was assigned

various projects and tasks that would transform him from a student to a professional engineer.

The intern was exposed to engineering practice, planning, design, reporting, operations,

research, testing, project management and business development. The intern worked in the

Corporate Engineering Group who are responsible for all engineering standards, processes and

developments across the entire business.

This report outlines the major projects that the intern was directly involved in and that relate

directly to the field of Electrical Engineering. This report documents the purpose of each

project, the engineering approach, summary of outcomes and the current status of the work.

The four projects covered in detail in this report are the following:

Cloudbreak Expansion Load Flow and Short-Circuit Study Cloudbreak Dragline Excavator Dynamic Study Solomon LED Lighting Pilot Project Transformer Factory Acceptance Testing

The final year engineering internship program between Murdoch University and Fortescue

Metals Group Limited was successful and worthwhile. The intern gained relevant industry

experience and the skills to carry out engineering based work professionally.


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Disclaimer

The collection of material contained within this report is independently the work of the author

unless otherwise referenced.

All work completed during the internship placement was carried out under the supervision of

industry supervisor, Cobus Strauss, and therefore remains the property of Fortescue MetalsGroup Limited.

I declare the following work to be my own work, unless otherwise referenced, as defined by

Murdoch Universitys Plagiarism and Collusion Assessment Policy.

Mr. Daniel Paino

Signed: Date:

Engineering Intern Murdoch University and Fortescue Metals Group Limited


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Acknowledgements

The Internship has been honestly a life changing experience and will successfully transform my

position from a student to a professional engineer. I feel very privileged to have work with the

following bodies and people and would like to take this opportunity to thank them.

Principal Electrical Engineer at Fortescue Metals Group, Cobus Strauss, who supervisedmy internship, provided great learning experiences, gave me the opportunity to

manage and work on my own projects, demonstrated what it takes to be a

professional engineer and supported me throughout the placement.

Corporate Engineering Group Manager at Fortescue Metals Group, Mark Botes, firstlyfor accepting the internship, providing support and managing my position over the

placement.

The Corporate Engineering Group at Fortescue Metals Group, for making me feelwelcome and part of the team.

Academic Chair and Senior Lecturer at Murdoch University, Dr. Gregory Crebbin, firstlyfor teaching and providing support over the 4 years of my engineering degree.

Secondly for supervising my internship and providing great assistance during the time

of my placement at Fortescue Metals Group.

My family and friends for understanding and supporting me over the past four years. Iunderstand that putting up with someone with an unpredictable lifestyle can be quite

challenging and I appreciate it.

Last but not least, my colleagues at Murdoch University who I have had the privilege ofworking and studying with over the past four years into the early hours of the

morning. You have all aided in my development in becoming a professional engineer.


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Table of ContentsExecutive Summary ....................................................................................................................... i

Disclaimer .................................................................................................................................... ii

Acknowledgements ..................................................................................................................... iii

List of Figures ............................................................................................................................... 3

List of Tables ................................................................................................................................ 4

1 Introduction ......................................................................................................................... 5

1.1 The Internship .............................................................................................................. 5

1.2 Fortescue Metals Group Limited .................................................................................. 5

1.3 Corporate Engineering Group ...................................................................................... 6

1.4 Report Limitations ........................................................................................................ 6

2 Internship Projects ............................................................................................................... 7

3 Cloudbreak Expansion Load Flow and Short-Circuit Study ................................................... 7

3.1 Background .................................................................................................................. 7

3.2 Methodology ................................................................................................................ 8

3.3 Results ........................................................................................................................ 12

3.4 Conclusion .................................................................................................................. 25

3.5 Current Status ............................................................................................................ 25

4 Cloudbreak Dragline Excavator Dynamic Study .................................................................. 27

4.1 Background ................................................................................................................ 27

4.2 Methodology .............................................................................................................. 28

4.3 Results ........................................................................................................................ 34

4.4 Conclusion .................................................................................................................. 41

4.5 Current Status ............................................................................................................ 42

5 Solomon LED Lighting Pilot Project .................................................................................... 43

5.1 Background ................................................................................................................ 43

5.2 Methodology .............................................................................................................. 44

5.3 Conclusion .................................................................................................................. 48

6 Transformer Factory Acceptance Testing ........................................................................... 49

6.1 Background ................................................................................................................ 49

6.2 Methodology .............................................................................................................. 51

6.3 Conclusion .................................................................................................................. 56

7 Internship Review .............................................................................................................. 57

Bibliography .............................................................................................................................. 58

Abbreviations ............................................................................................................................. 60


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Appendices ................................................................................................................................ 61

Appendix A - Cloudbreak Mine Power Distribution Single Line Diagrams .............................. 61

Appendix B - SCADA Cloudbreak Load Demand Information (15/08/2011 - 17/08/2011) ..... 62

Appendix C - AVK Alternator Specification Frame HV 80W Winding 83 .............................. 63

Appendix D - Cloudbreak PTW Load Flow and Short-Circuit Simulation Results................... 64

Appendix E - Cloudbreak PTW Short-Circuit Simulation Result for MC435 (SC-1)................ 65

Appendix F - SL-001 Power Station Expansion Switchboard Interconnection ..................... 66

Appendix G - Bucyrus 8750-81 Dragline Product Specification Sheet .................................... 67

Appendix H - Bucyrus 8750-81 Dragline Typical Real Power vs. Time Curve .......................... 68

Appendix I - Christmas Creek Power System General Single Line Diagram ............................ 69

Appendix J - Dragline Typical Real Power vs. Time Curve Modelling ...................................... 70

Appendix K - Cloudbreak Power System Dragline Excavator Study Single Line Diagrams .... 71

Appendix L - Cloudbreak Power System Dragline Excavator Study Results.......................... 72


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List of FiguresFigure 1-1 Fortescue Metals Group Limited Operations Map ..................................................... 5

Figure 1-2 Production Execution Strategy T155 for June 2013 ................................................... 6

Figure 2-1 Bucyrus 8750-81 Dragline Typical Real Power vs. Time Curve .................................. 27

Figure 2-2 Construction of PowerStore Flywheel ..................................................................... 29

Figure 2-3 PowerStore Flywheel Substation Layout................................................................ 30Figure 2-4 Case Study 1 Dragline Voltage (p.u) vs. Real Power Consumption (MW) ............... 34

Figure 2-5 Case Study 2A Dragline Voltage (p.u) vs. Real Power Consumption (MW) ............. 35

Figure 2-6 Case Study 2B Flywheel Voltage, Power and SOC Dynamic Response .................... 36

Figure 2-7 Case Study 2C Power Stations Dynamic Response .................................................. 37

Figure 2-8 Case Study 3A Dragline Voltage (p.u) vs. Real Power Consumption (MW) ............. 38

Figure 2-9 Case Study 3A Power Stations Dynamic Response ................................................. 39

Figure 2-10 Case Study 3B Power Stations Dynamic Response ................................................ 40

Figure 2-11 Case Study 3B 66kV Interconnection Loading ....................................................... 41

Figure 2-12 LED Lighting Pilot Project Communication ............................................................ 47

Figure 2-13 Cloudbreak Mine LED Lighting versus HPS Lighting ................................................. 48

Figure 2-14 5MVA 3-winding VSD transformer at ABB Singapore .............................................. 50

Figure 2-15 52MVA 2-winding power transformer at ABB Vietnam .......................................... 51

Figure 2-16 Ratio and Voltage Vector Relationship Test Circuit............................................... 52

Figure 2-17 Separate Source Voltage Withstand Test Circuit.................................................. 53

Figure 2-18 Measurement of No-Load Loss and No-Load Current Test Circuit........................ 54

Figure 2-19 Measurement of Winding Resistance................................................................... 55

Figure 2-20 Measurement of Load Loss and Impedance Voltage Test Circuit......................... 55


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List of TablesTable 2-1 Case Studies for Load Flow Analysis ........................................................................... 12

Table 2-2 LF-1 Switchgear Results............................................................................................ 12

Table 2-3 Cable Current De-rating Approach............................................................................ 14

Table 2-4 LF-1 Cable Loading Results........................................................................................ 14

Table 2-5 LF-1 Transformer Loading Results............................................................................. 14Table 2-6 LF-2 Switchgear Results............................................................................................ 15

Table 2-7 LF-2 Cable Loading Results........................................................................................ 17

Table 2-8 LF-2 Transformer Loading Results............................................................................. 17

Table 2-9 Additional Generation Calculation Information ......................................................... 18

Table 2-10 Case Studies for Load Flow Analysis ......................................................................... 20

Table 2-11 Switchgear Fault Currents Results for SC-1............................................................. 20

Table 2-12 Three-phase short-circuit variables .......................................................................... 22

Table 2-13 Peak Short-Circuit Current Calculation Variables ..................................................... 22

Table 2-14 Line-to-Earth Short-Circuit Current Calculation Variables ........................................ 23

Table 2-15 Switchgear Fault Currents Results for SC-2............................................................. 24

Table 2-16 Bucyrus 8750-81 Dragline Electrical Details for Typical Excavation Cycle ................ 27

Table 2-17 PowerStore Flywheel Specification........................................................................ 30

Table 2-18 Dynamic Study details of Case Studies ................................................................... 33

Table 2-19 Dragline Dynamic Case Study 2A Results ............................................................... 35


Table 2-20 Dragline Dynamic Case Study 2B Results ............................................................... 36

Table 2-21 Dragline Dynamic Case Study 2C Results ............................................................... 37


Table 2-23 Dragline Dynamic Case Study 3B Results ............................................................... 40

Table 2-24 Lighting Technology Comparison........................................................................... 43

Table 2-25 Project Stakeholders and Responsibilities .............................................................. 45

Table 2-26 Transformer Details for FAT at ABB Singapore ......................................................... 49

Table 2-27 Transformer Details for FAT at ABB Vietnam ........................................................... 50

Table A-1 Abbreviations ............................................................................................................. 60


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1 Introduction1.1 The InternshipThe purpose of the Internship is to enable the intern to satisfy the requirements of the

Bachelor of Engineering (Double Major in Electrical Power Engineering and Renewable Energy

Engineering) degree at Murdoch University. The intern will be exposed to the world of applied

engineering design, operations, development, projects and management which relate directly

to the engineering degree the intern is completing. The intern will gain experiences and skills

which will allow a smooth transition into the career of a professional engineer.

Over the period from August 2011 to May 2012, the intern carried out his internship

placement at Fortescue Metals Group Limited in Perth, Western Australia, in the Corporate

Engineering Group under the supervision of the Principal Electrical Engineer. The intern

worked both full-time and part-time over this period.

1.2 Fortescue Metals Group LimitedFortescue Metals Group Limited is the fourth largest iron ore producer in the world and only

shipped its first ore in May 2008. They have operations located in the Pilbara Region of

Western Australia comprising mine, port and rail infrastructure, as shown in Figure 1-1 below.

They hold tenements of over 88,000 square-kilometres and have a permanent workforce of

3,000 workers and 5,000 contractors. At present the iron ore production is carried out through

the Chichester Hub, specifically the Cloudbreak and Christmas Creek mines, and exported

through the Herb Elliot Port. This current mine process allows FMGL to successfully produce

55Mtpa.

Figure 1-1 Fortescue Metals Group Limited Operations Map


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FMGL is currently undertaking a major expansion, which will increase the production rate from

55Mtpa to 155Mtpa. This major expansion is known as project T155, and is scheduled to be

completed in June 2013. This will be achieved by increasing the production rate at the

Chichester Hub from 55Mtpa to 95Mtpa, and introducing another site called the Solomon Hub

comprising two mines sites, Firetail and Kings, which will produce 60Mtpa collectively. As a

result, the aggregate production capacity will be 155Mtpa. This production strategy is

indicated in Figure 1-2 below.

Figure 1-2 Production Execution Strategy T155 for June 2013

Future developments include introducing another site called the Western Hub, a second port

called Anketell, and a third mine within the Chichester Hub called Nyidinghu. These future

developments can potentially bring the FMGL iron production rate to 355Mtpa.

1.3 Corporate Engineering GroupThe Corporate Engineering Group is responsible for engineering standards, processes,strategies and development. The group consists of engineering management, principal

engineers through to graduate engineers and drafters covering civil, electrical and mechanical

disciplines. The group manages their own internal projects as well as being involved in the

expansion projects and business development.

1.4 Report LimitationsThis report documents the experiences, learning outcomes and project work carried out by the

intern during the course of the internship placement at Fortescue Metals Group Limited. The

report has been produced in accordance with the requirements of the ENG450 Final YearEngineering Internship Study Guide (H-period). Note that supplementary non-print material

and work has been attached to this report.


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2 Internship ProjectsOver the course of the Internship program, the intern was assigned a number of projects and

tasks. Due to word limitations not all projects and tasks carried out during the internship

placement are described in this report. The projects below relate directly to the majors of the

interns degree, and played a pivotal role in expanding the interns engineering knowledge and

skills:

Cloudbreak Expansion Load Flow and Short-Circuit Study Cloudbreak Dragline Excavator Dynamic Study Solomon LED Lighting Pilot Project Transformer Factory Acceptance Testing

3 Cloudbreak Expansion Load Flow and Short-Circuit Study3.1 BackgroundIn September 2009 FMGL were planning to expand the Cloudbreak mine from 35Mtpa to

45Mtpa and finally to 55Mtpa in a two stage expansion. This expansion would introduce new

mine equipment, infrastructure and processes, and as a result increase the electrical load of

the mine which would affect the loading on the power station, transformers and distribution

cables as well as the fault levels on the existing switchboards. In order to plan, evaluate and

execute this expansion and its electrical impact, FMGL engaged the Worley Parson Power

Division to carry out a load flow and short-circuit study, which they completed. However, this

two stage expansion plan did not go ahead as the Cloudbreak current and proposed T155production rate is only 40Mtpa.

In August 2011, the Corporate Engineering group engaged Worley Parson Power Division to

again carry out a new load flow and short-circuit study,as FMGL were introducing a new iron

ore processing facility called the Wet Front End. The Wet Front End Project is one of many

expansion projects FMGL are undertaking to ramp up production from 55Mtpa to 155Mtpa in

the Chichester Hub. The Wet Front End Project will allow direct processing of iron ore below

the water table and optimisation of the ore grade and volume, which will in turn extend the

life of the Cloudbreak Mine by approximately 3.5 years.

The purpose and objectives of this study are to determine the implications of this expansion

on the existing electrical infrastructure, specifically the loading and fault levels on the power

station, switchgear, main cables and distribution transformers in the Cloudbreak power

system.

The Cloudbreak power system generation and distribution arrangement is shown in Appendix

A in single line diagrams CB-10016-DR-EL-0003 Sheet 1 to 3.

The Cloudbreak power system is supplied by 18 reciprocating diesel engines (MTU 20V 4000

G62) directly coupled to individual alternators (AvK HVS1803W2). This also conforms with the

operating philosophy of the power station, which is n+2, meaning that at any given time one

generator will be out in maintenance and one will be redundant, resulting in 16 available


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generators. This arrangement allows the power station to have a continuous output rating of

27.9MW and prime output rating of 31.8MW (as defined by AS4594 Internal Combustion

Engines). This electrical power is generated at a voltage of 11kV, which is distributed through

three HV transformers (TF03, TF11 and TF12) at 22kV, a direct cable line to the camp at 11kV

and one power station auxiliary transformer (TF02) at 400V. The main 11kV station

switchboard is earthed by a 15.7zig-zag earthing transformer (TF01).

The generated power is distributed through TF11 and TF12 are transmitted through overhead

and underground cables, which connect to the main OPF switchboard, SW411, which

contributes to the largest portion of electrical loads and is where the Wet Front End loads will

be connected. The switchboard is segregated into two buses, SW411A and SW411B (incomers

from TF12 and TF 11 respectively), which are connected by a bus tie that is normally-closed.

SW411 distributes electrical power to Lump Stockpile, Crushing, Screening, Desand, Facilities

and ROM substations.

TF03 supplies power to the mine services, which has admin and workshop loads connected.

The camp O/H line transmits power to two workshops, a sewage-bore treatment plant and the

accommodation village, which consists of nine ring main units in a completed radial topology.

The Cloudbreak average load demand is 19.1MW and maximum load demand is 23.2MW. The

Wet Front End Project will introduce 3 new scrubbing/screen modules to wash clay from the

ore feed, redirect process conveyors and add capacity to the thickeners to handle higher water

loads. According to the project load list, this enhancement will add electrical loads to the

Lump (SW454), Screening (SW421) and Desands (SW426) switchboards at a net magnitude of

13.5MW running load.

3.2 MethodologyConsignment with Worley Parsons

From start to finish, the intern was on a consignment with Worley Parson Power Division,

which involved the data collection, modelling, simulation, reporting and project management

of the load flow and short-circuit study. This arrangement allowed the intern to communicate

the project developments between the FMGL Principal Electrical Engineer and Worley Parsons

project team, which consisted of two Senior Electrical Engineers. The intern met on a daily

basis with the Worley Parsons project team and had a workstation at their office.

Software and Existing ModelThe site Electrical Utilities group kept an as-built model using the power system software

Power*Tools for Windows (PTW) v6.5.0.0 from SKM, which was maintained by site electrical

engineers. However the load flow and short-circuit study will only use this as-built model as a

reference to ensure that all inputs and modelling are reliable and as accurate as possible.

Fortunately, the Worley Parsons Power Division principally use Power*Tools for Windows

(PTW) v6.5.0.0 from SKM for power system modelling. The intern was trained on the software

by one of the senior electrical engineers over a period of a day. This involved how to input data

for generators, transformers, cables and loads (motors, VSD, UPS and feeder) and how to

simulate load flow and short-circuit calculations as well as output results.


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Data Collection

The intern collected as-built drawings from the FMGL document management system, PIMS.

The intern collected all asbuilt single line diagrams from generation through to load

distribution, cable schedules, load lists and manufacturer equipment specifications.

The intern had the opportunity to visit the Cloudbreak mine over a three day period, which

involved a supervised tour of power station, distribution line route and the OPF substations.

This allowed the intern to further verify and collect the following information:

Plant operating strategy Generation, distribution and equipment single line diagrams Cable schedules Cable sizing calculations Load list for existing and future loads Load and generation dynamics Protection settings All major equipment specifications including generators, transformers, switchgear,

variables speed drives and motors.

The intern had previously worked as a Vacation Student for FMGL at port operations the

summer before, and had knowledge of the SCADA/process control software that FMGL

utilized. The SCADA software that FMGL has installed is CimView by General Electric. This prior

knowledge allowed the intern to collect the power systems loading magnitudes for the four

main HV feeders (TF03, TF11, TF12 and the Camp O/H line) from the power station and the

main substations (SW454, SW435, SW451, SW431, SW421 and SW426) below switchboard

SW411. This load demand data (attached in Appendix B) was then inserted in the Microsoft

Excel and organised to aid in inputting the data into the power system model on PTW.

Building the Model

The total connected loads for each busbar in the model were calculated based on as-built

single line diagrams, and then the equivalent load factor was applied to loads connected to

each busbar to ensure it will match the readings collected from SCADA. An additional diversity

factor of 87.5% has been applied to the loads below SW411. This diversity factor has been

applied to simulate the reality that it is highly unlikely for each feeder to experience maximum

demand simultaneously and for the plant overall loading to match the power station SCADA

loading. Once the existing loads magnitudes were added to the model the WFE project loads

were added based on the WFE project load list, with a diversity factor of 90%.

Transformer impedance values were based on transformer nameplate inspection from the site

visit. However, where confirmation was not achieved site as-built single line diagrams were

used. Voltage ratio and power capacity values were added to the model as per as-built single

line diagrams. All tap positions of transformers were modelled at position zero, meaning 0%

tap. The Wet Front End project transformers capacity, voltage ratio and impedance values

were supplied through communication with design and construct project teams during the site

visit.

All cables were added to the power system model with respect to material, size, length, and

quantity as per site as-built single line diagrams. The WFE Projects new cables have been


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added to the power system software as per Cloudbreak Enhancement Project Cable Schedule,

with impedances obtained from Olex manufacturer catalogues.

Generator Reactance

As stated in the background section 3.1, the generation is provided by 18 reciprocating diesel

engines (MTU 20V 4000 G62) directly coupled to individual alternators (AvK HVS1803W2). The

reciprocating diesel engine acts as the prime mover which produces rotating mechanical

power to the rotor of the alternator. This arrangement is known as a synchronous generator

where the main magnetic field is set up by dc current called the field current, which flows

through the rotor windings. As the rotor rotates, it forces the magnetic field to rotate, causing

the windings on the stator (armature) to experience a time-varying flux that induces an

alternating voltage across the output terminals of each of the stator (armature) windings.

When modelling generators for fault analysis we are concerned with a temporary difference

between the rotor speed and voltage frequency. This effect is modelled by the alternators sub-

transient reactance Xd. The manufacturers alternator specification is attached as Appendix C.

However, while the Cloudbreak power station synchronous generators have an individual

power rating of 2,607kW, they only operate in continuous mode at 1,742 kW (data collected

from site visit), and because the load flow and short-circuit analysis will be simulated with the

generators in continuous mode, the sub-transient reactance Xd need to be re-calculated. This

calculation is shown below.

. = 0.8

= 3259

"() = 0.163

= . = 3259 0.8 = 2607

= 1742

(%) =

=17422602

= 66.95%

"() = 66.95% "() = 66.95% 0.163 = 0.109

This operating calculation also applies to the synchronous generators transient reactance, Xd,

which is shown in the calculation below.

() = 66.95% () = 66.95% 0.221 = 0.148

Assumptions

The overall power system network model was based on the following assumptions:

Average power output for each generator is assumed to be 1742kW. Peak power outputfor each generator is assumed to be 2123kW;

The X/R ratio for transformer impedances have been assumed as per AS3851; Transformer taps have been modelled as per site verification, and if unavailable a tap

setting of 3 (i.e. 0%) has been assumed; VSDs have been modelled with a power factor of 0.93 as per the ABB ACS800 catalogue; Motor loads have been modelled to have a power factor of 0.85;


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Feeder loads have been modelled to have a power factor of 0.9; UPS loads have been modelled to have a power factor of 0.95; Lumped motor loads have been assumed to have a R/X ratio of 0.42 and a I(locked

rotor)/I(full load) ratio of 5 as perAS3851: The calculation of short-circuit currents in

three-phase a.c. systems;

Load factor for MC441 connected loads has been assumed to be 0.5863, approximatingoverall load factor from load list with a diversity factor applied;

DB717 Main Sewage Treatment Plant is assumed to have a motor load of 50kWconnected and the SS711 package substation assumed to have a lumped 200kW motor

load connected to simulate the worst case power demand for transformer TF03 as per

SCADA profile;

Package substation SS714 is assumed to have a 750kW lumped load connected toSW714, as previously modelled in the existing as-built model;

HPGR circuit is assumed to have a 2500kW lumped load connected to CSI_HPGR_02, aspreviously modelled in existing as-built model;

Railcar unloading package substation SS718 is assumed to have a 66kW lumped motorload as previously modelled in existing as-built model;

Camp load has been simplified as a 1400kW lump motor load, and 450kW lump feederload connected to RM700, to simulate worst case load demand as per SCADA profile. As

a result of this, no load has been modelled connected to RM721 and further

downstream;

Emergency Generators shown on FMG Cloudbreak as-built single line diagrams are notmodelled for the purpose of the study, due to unavailability of data;

The average Wet Front End Project load is assumed to be equal to the peak load of theWet Front End Project load.

The load flow analysis was based on the following test criteria and assumptions:

Minimum and maximum voltage levels for all busbars and consumer terminals duringnormal running operation shall be within 90% to 110% of system nominal voltage;

The synchronous generators were lumped and modelled with an operational voltage atthe 11kV generation busbar with 1pu;

The largest DOL motor on each switchboard is modelled and the remaining DOL motorloads are aggregated into a lumped motor load;

Feeder, VSD and UPS loads are aggregated into separate lumped loads for eachswitchboard;

Typical data are used for simulating some equipment due to the lack of sufficient vendortest reports and data sheets for specific parameters;

VSDs are modelled as an equivalent constant kVA load.The short circuit analysis was based on the following test criteria and assumptions:

The IEC 60909 method was selected for the short circuit calculations; For calculation of maximum and minimum short circuit currents, voltage factor c as per

IEC 60909: Short-circuit currents in three-phase a.c. systemsis applied; All LV motors, with the exception of the largest motor on each bus are modelled without

cables with a locked rotor current of 5 times rated full load current, as specified in

AS3851 The calculation of short-circuit currents in three-phase a.c. systems;

The zero sequence impedance was assumed to be 90% of the transformers positivesequence impedance.


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3.3 ResultsLoad Flow Analysis

The purpose of the load flow analysis is to assess the voltage regulation and loading based on

acceptable tolerances for switchgear, equipment and conductors. The load flow analysis was

carried out separately through two different power system scenarios as listed in Table 2-1.

Table 3-1 Case Studies for Load Flow Analysis

Case Study Description Plant Loading

LF-1 Existing Load and Generation 23.2MW

LF-2 Existing Load and Wet Front End Project 35.65MW

Load Flow 1 Existing Load and Generation

LF-1 was performed to determine the minimum steady state voltages for the Cloudbreak mine

power system for existing plant operating conditions. All results should be acceptable as the

Cloudbreak mine power system is currently operating. The Cloudbreak mine power system

configuration for LF-1 is as follows:

Sixteen 1.742MW (average) 11kV generators operating and all bus-ties are open; TF11 and TF12 tapping are set at 0% Overall plant loading is based on 23.2MW electrical load demand, which corresponds

to the peak maximum electrical demand during normal operation of the Cloudbreak

Mine.

Cloudbreak PTW LF-1 Simulation Results are attached in Appendix D.

The results for the main switchboards voltage loading are outlined in Table 2-2 for case study

LF-1.

Table 3-2 LF-1 Switchgear Results

Switchgear Nominal Voltage (kV) Steady State Voltage (%) Acceptability

SW411A 22.000 97.2 Acceptable

SW411B 22.000 96.1 Acceptable

SW454 22.000 97.2 Acceptable






MC454 0.400 100.3 Acceptable







CSI-HPGR 22.000 95.9 Acceptable

TX02_LV 0.400 95.9 Acceptable



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SW437 () 0.690 99.3 Acceptable

SW437 (Y) 0.690 99.3 Acceptable
















CAMP 11.000 97.3 Acceptable

SB-731 0.400 107.8 *Acceptable



* High voltage levels for SB-731 and SB-732 are due to simulation of no load or very small load

on the busbar.

The LF-1 Switchgear results indicate that voltage levels for all switchgear busbars in the

Cloudbreak Mine network, under existing operating conditions, are within the allowable limits.

However, as mentioned in the methodology section, a diversity factory of 85.7% has been

applied against the loads to simulate realistic load magnitudes, therefore it is possible that

these voltages could be higher. If load data was available from SCADA at every MCC and VSD

switchboard, then the results would be more accurate. However, obtaining this amount of

information would be quite time consuming, and the project schedule did not allow time to

carry this out.

The results for the loading of the major 22kV cables in case study LF-1 are summarised in Table

2-4. All major 22kV cables are operating below the rated thermal capacity. The thermal

capacity of the cables has been calculated in PTW using the approach followed in Table 2-3

regarding de-rating factors. The de-rating factors correspond to those specified inAS3008.1

Selection of Cable for Alternating Voltages up to and including 0.6/1 kV.


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Table 3-3 Cable Current De-rating ApproachMajor Cable De-rating Factor for SW421-P-01 in PTW Model as per AS3008.1

Cable Arrangement and Type 1 x 1C 240mm Cu XLPE/AWA

Buried Direct Trefoil for 342m

Conductor Temperature 90

Soil Temperature 35

Ambient De-rating in Ground 0.93

Depth of Laying in Ground 2m

De-rating of Depth of Cable in Ground 0.88

Distance Between Cables 0.45m

Number of Circuits 1

Total Number of Circuits in Trench (Worst Case) 6

De-rating of Multiple Circuits 0.72

Total De-rating Factor = 0.93 x 0.88 x 0.72

= 0.59

Cable Current Rating 450A

De-rated Cable Current Rating 265A

(as outlined in Table 2-4)

Table 3-4 LF-1 Cable Loading Results

Cable ID From To Capacity (A) Loading (%)OPF2-1 618 59.1

OPF1-1 618 44.0

OPF1 OPF1-1 OPF1-4 1226 22.2

OPF2 OPF2-1 OPF2-14 1226 29.8

SW411-P-03 OPF1-14 SW411 918 28.0

SW411-P-04 OPF2-14 SW411 918 39.9

SW421-P-01 SW411 SW421 265 38.1

SW426-P-01 SW411 SW426 313 34.8

SW431-P-01 SW411 SW431 648 16.8

SW435-P-01 SW411 SW435 648 20.4SW451-P-01 SW411 SW451 274 35.0

SW454-P-01 SW411 SW454 378 7.7

The results for the loading of the major transformers for LF-1 are summarised in below Table

2-5. All major transformers loadings are acceptable and below the rated power capacities.

Table 3-5 LF-1 Transformer Loading Results

Transformer ID Transformer Rating (kVA) Transformer Loading (%)

TF03 3000 11.0

TF11 27000 51.6TF12 27000 38.4

TF413 2000 34.9


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TF414 2500 43.1

TF421 2000 22.6

TF422 2000 28.7

TF423 5000 56.4

TF426 2000 22.8

TF427 5000 14.5

TF428 2000 20.3

TF429 5000 27.9

TF430 2000 16.9

TF431 2000 46.0

TF432 5000 28.0

TF433 5000 27.7

TF435 2000 60.2

TF437 5000 18.5

TF439 5000 9.5

TF441 2000 25.2

TF442 5000 18.6

TF451 2000 28.3

TF452 5000 61.8

TF453 5000 24.7

TF454 2000 12.8

TF455 5000 11.2

TF456 5000 5.6

Load Flow 2 Existing Load and Wet Front End Project

LF-2 was performed to determine the minimum steady state voltages for the Cloudbreak mine

power system for existing plant operating conditions plus the addition of the Wet Front End

project loads. An extra four generators have been added the power station switchboard to

handle the Wet Front End load requirements. The Cloudbreak mine power system

configuration for LF-2 is as follows:

Twenty 1.742MW (average) 11kV generators operating and all bus-ties are open; TF11 and TF12 tappings are set at -2.5%; Overall plant loading is based on 35.65MW electrical load demand, which corresponds

to the peak maximum electrical demand expected during normal operation when the

Wet Front End Project becomes operational at the Cloudbreak Mine.

Cloudbreak PTW LF-2 Simulation Results are attached in Appendix D.

The results for the main switchboards voltage loading are outlined below in Table 2-6 for case

study LF-2.

Table 3-6 LF-2 Switchgear Results

Switchgear Nominal Voltage (kV) Steady State Voltage (%) Acceptability

SW411A 22.000 97.0 Acceptable

SW411B 22.000 97.2 Acceptable





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SW505** 22.000 97.0 Acceptable

TF505A/B/C** 0.690 97.6 Acceptable


MC-507** 0.400 98.7 Acceptable

MC-508** 0.400 98.9 Acceptable








CSI-HPGR 22.000 95.8 Acceptable






SW437 () 0.690 100.5 Acceptable





SW427 () 0.690 100.2 Acceptable



SW429 () 0.690 100.7 Acceptable






SW443 ()** 0.690 100.4 Acceptable

SW443 (Y)** 0.690 100.5 Acceptable





CAMP 11.000 97.3 Acceptable




* High voltage level is due to simulation of no load or very small load on the busbar.

** New Wet Front End project switchgear


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The LF-2 Switchgear results indicate that the voltage levels for all switchgear busbars in the

Cloudbreak Mine power system under existing operating conditions plus the additional Wet

Front End project loads are within the allowable limits. However, in order to maintain

allowable voltage levels at switchgear SW411A and SW411B, tapping for both TF11 and TF12

need to be set at -2.5%.

The results for the loading of the major 22kV cables in case study LF-2 are summarised in Table

2-7. All major 22kV cables are operating below the rated thermal capacity. The thermal

capacity of the cables was calculated using the same approach as outlined in LF-1.

Table 3-7 LF-2 Cable Loading Results

Cable ID From To Capacity (A) Loading (%)

TF11 OPF2-1 618 80.0

TF12 OPF1-1 618 82.0

OPF1 OPF1-1 OPF1-4 1226 41.4

OPF2 OPF2-1 OPF2-14 1226 40.3

SW411-P-03 OPF1-14 SW411 918 53.6

SW411-P-04 OPF2-14 SW411 918 53.8

SW421-P-01 SW411 SW421 265 37.7

SW426-P-01 SW411 SW426 313 77.0

SW431-P-01 SW411 SW431 648 16.7

SW435-P-01 SW411 SW435 648 20.4

SW451-P-01 SW411 SW451 274 35.0

SW454-P-01 SW411 SW454 378 69.8

The results for the loading of the major transformers for LF-2 are summarised in Table 2-8. All

major transformer loadings are acceptable and are below the rated power capacity.

Table 3-8 LF-2 Transformer Loading Results

Transformer ID Transformer Rating (kVA) Transformer Loading (%)

TF03 3000 11.0

TF11 27000 71.6

TF12 27000 73.5

TF413 2000 34.5

TF414 2500 42.6

TF421 2000 23.1TF422 2000 28.3

TF423 5000 55.7

TF426 2000 18.6

TF427 5000 18.6

TF428 2000 43.2

TF429 5000 13.7

TF430 2000 23.5

TF431 2000 45.4

TF432 5000 27.7

TF433 5000 27.8

TF435 2000 60.2


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TF437 5000 18.2

TF439 5000 41.6

TF440 5000 37.8

TF441 2000 25.2

TF442 5000 18.4

TF443 5000 31.1

TF451 2000 28.4

TF452 5000 61.9

TF453 5000 24.8

TF454 2000 12.8

TF455 5000 11.2

TF456 5000 5.6

TF505A 1750 78.0

TF505B 1750 78.0

TF505C 1750 78.0

TF506 5000 66.5TF507 2000 41.5

TF508 2000 37.5

Additional Generation Calculation

The load flow simulations in PTW indicate that the additional Wet Front End Project loads

increase the maximum demand to 35.65MW from an existing demand of 23.2MW. As the

Cloudbreak power station operates on an n+2 configuration with 18 generators, it is not

capable of supplying this load. The determination of the minimum number of additional

generators required to meet the additional load demands will consider both the peak and

average load demands.

Each diesel generator is capable of supplying an average load of 1.742MW, with a peak of

2.123MW. The average load experienced at the power station in the existing load scenario (LF-

1) has been calculated from the SCADA outputs (Appendix B) and is 18.3MW. However this

magnitude excludes the operation of the Lump Circuit (SW454), which was not operating

during the period that the SCADA outputs were taken. The Lump Circuit (SW454) average load

was calculated from separate SCADA outputs to be 0.45MW. No data was available for the

average load of the Wet Front End Project, so the conservative assumption was made that the

average of the Wet Front End Project load is equal to the peak load of 12.43MW.

Table 3-9 Additional Generation Calculation Information

Variable Type Magnitude Comments

() Average GeneratorPower

1.742MW Confirmed with

power station

operators.

() Peak GeneratorPower

2.123MW Confirmed with

power station

operators.

() Average Existing Load 18.75MW Addition of ExistingLoad 18.3MW and

Lump Circuit Load

0.45MW.


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() Average WFE Load 12.42MW Same as peakmagnitude

conservative.

() Peak Existing Load 23.22MW Load Flow 1 powerstation supply.

() Peak WFE Load 12.42MW Load Flow 2 power

station supply.() Spinning Reserve 1.9MW From power station

due diligence report.

The calculation of the minimum number of generators required()to supplythe additional average WFE load demand and spinning reserve is outlined below.

() =() + () + ()

() = 18.75 + 12.42 + 1.9

() = 33.1

() =()()

=33.11.742

= 19.0

The calculation of the minimum number of generators required()to supply theadditional peak WFE load demand and spinning reserve is outlined below.

() =() + () + ()

() = 23.22 + 12.42 + 1.9

() = 37.55

() =()()

=37.552.123

= 17.7

The power station is therefore required to supply an average load of 31.18MW and a peak load

of 35.65MW. The minimum number of generators at 1.742MW required to supply the average

load is 19. With the current configuration of 16 available (2 generators out of service) an extra

3 generators are required to be installed at the power station. However, it was agreed

internally that one additional generator would be included, as the change in operating

philosophy at the power station was based on machine maintenance, and an n+3 configurationwould suit better (2 in maintenance and 1 redundant). As a result, the power station will need

an extra 4 generators (22 in total) installed o satisfy the increase load demand from the WFE

expansion.

Short-Circuit Analysis

The short-circuit analysis is concerned with the currents that flow as a result of a short circuit,

and is calculated at each switchgear as per IEC 60909 standard for three phase balanced and

unbalanced short circuit conditions. IEC 60909 short-circuit calculation methodology complies

with requirements ofAS3851 The calculation of short-circuit currents in three-phase a.c.

systems. The calculation of short circuit currents includes the short circuit currentcontributions from the generators and from induction motors.


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The minimum and maximum fault currents have been calculated considering the following

fault scenarios:

Three-phase to ground fault (LLLE) Single-phase to ground fault (LE) Line-to-line fault (LL) Line-to-line to ground fault (LLE)

For each of the fault scenarios above, a voltage c-factor was applied in accordance with IEC

60909. The voltage factor (c) represents a conservative method of taking into account the

effects of variation of voltage, changing transformer taps, capacitance and the loads.

Earth fault currents on 11kV and 22kV systems are limited by the earthing zig-zag transformer

TF01. LV systems are solidly earthed at the system star point and can generate very high

currents.

The short-circuit analysis was carried out separately through two different power system

scenarios as listed in Table 2-10.

Table 3-10 Case Studies for Load Flow Analysis

Case Study Description Comments

SC-1 Maximum Short-Circuit Current for

Existing System SW411 bus tie is closed 18 generators are in service Plant loading 23.2MW (LF-1)

SC-2 Maximum Short-Circuit Current for

Wet Front End Project

SW411 bus tie is closed 22 generators are in service Plant loading 35.65MW (LF-2)

Short-Circuit 1 - Short-Circuit Current for Existing System

Cloudbreak PTW SC-1 Simulation Results are attached in Appendix D.

The results regarding the maximum (LLLE Short-Circuit) and minimum (LE Short-Circuit) fault

currents for existing switchgear in case study SC-1 are outlined in Table 2-11.

Table 3-11 Switchgear Fault Currents Results for SC-1

Switchgear

Operating Scenario SC-1 Switchgear Rating

Acceptability

Ik" LLLE Ip Ik" LE ib ip1/2

cycle

Sym

Current

(kA)

Peak

Asym

Current

(kA)

1/2

cycle

Sym

Current

(kA)

Symm

Breaking

Current

Max

Asym

Current

(kA)

Station HV Switchboard 22.8 55.6 0.4 25kA 3s 62.5kA

Station LV Switchboard 25.1 60.5 26.2 50kA 1s 105kA

SW411A 6.6 15.8 0.5 25kA 3s 62.5kA

SW411B 6.6 15.9 0.5 25kA 3s 62.5kA

SW454 6.6 15.7 0.5 25kA 3s 62.5kASW451 6.6 15.3 0.5 25kA 3s 62.5kA

SW435 6.6 15.8 0.5 25kA 3s 62.5kA


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SW431 6.6 15.8 0.5 25kA 3s 62.5kA

SW426 6.6 15.7 0.5 25kA 3s 62.5kA

SW421 6.6 15.5 0.5 25kA 3s 62.5kA

SW455 25.4 59.9 50kA 1s 105kA

SW456 25.5 60.5 50kA 1s 105kA

MC451 44.1 101.2 44.3 50kA 1s 105kA

SW452 25.2 59.7 50kA 1s 105kA

MC435 55.9 123.2 52.1 50kA 1s 105kA Unacceptable

SW433 25.3 60.3 50kA 1s 105kA

MC431 53.8 119 50.4 50kA 1s 105kA Unacceptable

SW432 25.4 60.3 50kA 1s 105kA

SW437 () 25.5 60.7 50kA 1s 105kA

SW437 (Y) 25.5 60.7 50kA 1s 105kA


SW427 () 25.5 60.6 50kA 1s 105kA

SW427 (Y) 25.5 60.6 50kA 1s 105kAMC428 43.2 99.1 43.5 50kA 1s 105kA

SW429 () 25.5 60.3 50kA 1s 105kA

SW429 (Y) 25.5 60.3 50kA 1s 105kA

MC430 44.1 101 44.1 50kA 1s 105kA

SW439 () 25.6 60.7 50kA 1s 105kA

SW439 (Y) 25.6 60.7 50kA 1s 105kA

MC421 43.1 99.3 43.6 50kA 1s 105kA


SW423 () 26.9 63.6 50kA 1s 105kA

SW423 (Y) 26.9 63.6 50kA 1s 105kA

MC441 40.7 92.9 41.7 50kA 1s 105kA

The Switchgear Fault Currents Results for SC-1 indicate that the majority of the HV & LV

switchgear ratings in the Cloudbreak Mine substations are appropriate for the maximum

system short circuit currents. The results indicated that MC431, MC435, MC426 and MC422

exceed the equipment rating and require further investigation and possible corrective action.

The unacceptable fault ratings are listed below:

MC431 (107.6% of the rating)

MC435 (111.8% of the rating)

MC426 (100.9% of the peak rating)


Calculation of Fault Currents for MC435

The PTW Short-Circuit Simulation Results for MC435 (SC-1) are attached in Appendix E.

The fault levels on the switchgear have been calculated in PTW model using the approach

given below. This approach corresponds toAS3851: The calculation of short-circuit currents in

three-phase a.c. systems.


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Three-phase short-circuit (LLLE) Clause 8.4.2 (A20) of AS3851

" =

3

Table 3-12 Three-phase short-circuit variables

Three-phase short-circuit variables

" Initial symmetrical short-circuit current amplitude (r.m.s.)

Voltage factor as per section 5.2 of AS3851 Base three-phase apparent power

Per unit symmetrical short-circuit impedance Nominal system voltage, line-to-line (r.m.s.)

= 1.1

= 100

= 2.84

= 400

" () =1.1 100 106

2.84 400 3= 55.905

" () = 55.860

(%) =" () " ()

" ()

55.905 55.86055.860

= 0.081%

Peak short-circuit current for LLLE - Section 8.5.2.1 of AS3851

= " 2

= 1.02 + 0.983/

Table 3-13 Peak Short-Circuit Current Calculation Variables

Peak short-circuit current for LLLE variables

Peak short-circuit current contribution a three-phase short-circuit" Initial symmetrical short-circuit current amplitude (r.m.s.)

Factor for the calculation of the peak short-circuit current

Resistance to Reactance Ratio of the system

" () = 55.860

= 0.20

= 1.02 + 0.9830.20 = 1.5578


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() = 1.5578 55.860 103 2 = 123.07

() = 123.16

(%) =123.07 123.16

123.16=0.07%

Line-to-earth short-circuit - Clause 8.4.5 (A33) of AS3851

" = 3

(0) + (1) + (2)

Table 3-14 Line-to-Earth Short-Circuit Current Calculation Variables

Line-to-earth short-circuit variables

" Initial symmetrical short-circuit current amplitude (r.m.s.)

Voltage factor as per section 5.2 of AS3851 Base three-phase apparent power

Nominal system voltage, line-to-line (r.m.s.)() Per unit zero-sequence impedance() Per unit positive-sequence impedance() Per unit negative-sequence impedance

= 1.1

= 100

= 2.84

= 400

(0) = 3.43

(1) = 2.84

(2) = 2.88

" () =1.1 100 106 3

400 (3.43 + 2.84 + 2.88)= 52.06

" () = 52.05

(%) =52.06 52.05

52.05= 0.081%


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For the following HV and LV switchgear, the apparent short circuit current levels are very high

and exceed 90% of the equipment rating:

11kV Main Switchboard (91.2% of the rating)





Short-Circuit 2 - Short-Circuit Current for Wet Front End Project

Cloudbreak PTW SC-2 Simulation Results are attached in Appendix D.

The results regarding the maximum (LLLE Short-Circuit) and minimum (LE Short-Circuit) fault

currents for WFE switchgear in case study SC-2 are outlined in Table 2-15.

Table 3-15 Switchgear Fault Currents Results for SC-2

Switchgear

Operating Scenario SC-2 Switchgear Rating

Acceptability

Ik" LLLE Ip Ik" LE ib ip

1/2 cycle

Sym

Current

(kA)

Peak Asym

Current

(kA)

1/2 cycle

Sym

Current

(kA)

Sym

Breaking

Current

Max

Asym

Current

(kA)

Station HV

Switchboard

27.9 67.8 0.41 25kA 3s 62.5kA Unacceptable

SW411A 7.6 17.9 0.45 25kA 3s 62.5kA

SW411B 7.6 17.9 0.45 25kA 3s 62.5kA

SW506 25.2 59.4 50kA 1s 105kA

MC507 48.5 107.3 48.6 65kA 1s 143kA

MC508 48.7 107.8 48.7 65kA 1s 143kA

SW427* 25.7 60.9 50kA 1s 105kA

SW440 26.1 61.3 50kA 1s 105kA

MC428* 43.4 99.4 43.6 50kA 1s 105kA

MC430* 44.3 101.4 44.3 50kA 1s 105kA

SW443 () 44 99.6 50kA 1s 105kA

SW443 (Y) 43.7 95.4 50kA 1s 105kA

* Existing switchgear with direct WFE loads connected.

As the power station switchboard now has 22 generators connected, the fault levels have

exceeded the switchboard rating and because this arrangement is not practical the

downstream switchgear results are not relevant. This issue can be potentially resolved by

installing a current limiting device between the existing power station switchboard and a new

switchboard with the new generators connected. The solution to this problem is covered later

in this report.


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3.4 ConclusionThe Cloudbreak expansion load flow and short-circuit study was carried out to evaluate firstly

the existing operation of the power system and the effect of the additional loads due to the

Wet Front End Project on the power system. This evaluation involved determining the required

ratings of major electrical equipment and acceptable power generation capacity.

The load flow analysis indicated that under the existing operation scenario (LF-1) a maximumoverall load of 23.2MW is expected with 16 generator units running and 2 standby generators

in n+2 configuration. The addition of the Wet Front End Project will add a loading of 12.43MW

to the Mine power system. This additional load requires a minimum of three 1.742MW

(average) generators, which will need to be added to the plant power generation. It was

recommended that a minimum of four 1.742MW (average) generators be added to the plant

power generation which will further provide a minimum spinning reserve of 1.9MW for an n+3

configuration and ensure acceptable electrical system stability. The load flow analysis results

indicate that the voltage magnitudes and loadings on all major equipment are acceptable.

The short-circuit analysis indicated that the 11kV power station HV switchboard with fouradditional generators will result in potential fault levels on the switchboard that are above the

switchgear ratings and are therefore unacceptable. The existing scenario short circuit analysis

(SC-1) indicated that some switchgear ratings are unacceptable specifically MC431, MC435,

MC426 and MC422, as the short-circuit currents exceeded the switchgear rating. Furthermore,

the short-circuit currents experienced on switchgear MC421, MC428, MC430 and MC451 are

greater than 90% of the switchgear rating. As a result it was recommended by the Worley

Parsons Power Division that these particular busbars to be further analysed and corrective

measures to be put in place if needed.

Taking into account the issues identified above in the load flow and short-circuit study, the

following recommendationswere revised:

Installation of four 1.742MW (average) generators as per existing type on a new 11kVswitchboard, with a current limiting device between the switchboard and the existing

11kV HV power station switchboard to reduce and eliminate fault contribution. Also,

to further balance the number of generators connected by having an even quantity of

generators on both the existing (11 generators) and proposed (11 generators) power

station switchboards.

The PTW Cloudbreak mine power system model needs to be updated specifically toeliminate the applied load factor and to determine the operational loading on each

MCC and busbar to improve the accuracy for future simulations.

Determine the operational short circuit values of switchgear exceeding or within 90%the equipment rating (i.e. MC431, MC435, MC422, MC426, MC421, MC428, MC430,

and MC451).

3.5 Current StatusAs outlined above, the load flow and short-circuit study identified three issues that FMGL

needed to resolve in order to carry out the Wet Front End Expansion. The following actions are

currently being carried out to rectify these issues. These actions correspond to therecommendations identified from the load flow and short-circuit study.


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Power Station additional generation requirements and switchgear rating

As outlined in the additional generation calculation section of the results, a further four

generators need to be installed in order to supply the extra 12.42MW peak load from the WFE

expansion and to satisfy the spinning reserve requirement of 1.9MW . Also, the 11kV power

station switchboard will exceed its current switchgear rating if four generators are connected.

Attached in Appendix F is the proposed FMG approved generation arrangement for the power

station. The proposed design includes an additional four generators and three existing

generators to be installed on a new 40kA rated switchboard which is connected to the existing

switchboard by a current limiting fuse. Also, feeder TF12 will be disconnected from the existing

HV power station switchboard to be connected directly to the new HV power station

switchboard, as well as a new earthing transformer and auxiliary switchboard.

Various downstream Motor Control Centre switchgear ratings

The determination of the operational short circuit values for various motor control centre

switchgear which exceed or are within 90% the equipment rating (i.e. MC431, MC435, MC422,

MC426, MC421, MC428, MC430, and MC451) are currently being studied using power system

software PowerFactory by DIgSILENT. This involves a more detailed short-circuit calculation

where the model will include more accurate input information such as specific line lengths,

manufacturer specified motor contributions which include realistic de-rating factors, and load

magnitude which related operational behaviour and data. This study is currently being carried

out, and based on the results the decision will be made on whether the motor control centre

switchgear rating needs to be upgraded or not.


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4 Cloudbreak Dragline Excavator Dynamic Study4.1 BackgroundFMGL is interested in deploying a dragline excavator as it will increase the productivity of their

Cloudbreak mine site. A dragline is an excavating machine that can perform strip mining at a

very productive rate. Draglines offer the lowest material removal cost and are the most

versatile excavating system in the mining industry. The particular dragline to be implemented

into the FMG mining environment has a dynamical power cycle profile and the power is to be

supplied through high voltage trailing cables from Cloudbreak Power Station. The dragline

manufacturer is Bucyrus; the product specification sheet is attached in Appendix G. The

dragline performs the following five exercises outlined in Table 2-16 during its excavation

cycle, which takes 60 seconds.

Table 4-1 Bucyrus 8750-81 Dragline Electrical Details for Typical Excavation Cycle

Bucyrus 8750-81 Dragline Electrical Details for Typical Excavation Cycle

Exercise State of DraglinePower

Peak PowerMagnitude (kW)

Exercise duration/period(seconds)

Load Bucket Drag Consumption 23,970 13.2/0 13.2

Hoist and Swing Consumption 28,600 24.0/13.2 37.2

Stop Swing and Dump Regeneration 4,100 4.2/37.2 41.4

Swing Back and Lower Consumption 12,200 11.4/41.4 52.8

Stop Swing Back and

Position for next cycle

Regeneration 17,160 7.2/52.8 60

This typical excavation cycle is graphically represented in Figure 2-1.

Figure 4-1 Bucyrus 8750-81 Dragline Typical Real Power vs. Time Curve

-18000

-15000

-12000

-9000

-6000

-3000

0

3000

6000

9000

12000

15000

18000

21000

24000

27000

30000

0 5 10 15 20 25 30 35 40 45 50 55 60

RealPower

(kW)

Time (sec)

Bucyrus 8750-81 Dragline Typical Real Power vs. Time Curve


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Given the draglines high power consumption, regenerative behaviour and dynamic cycle,

FMGL engaged DIgSILENT Pacific to perform a study to evaluate the dynamic stability of the

Cloudbreak Mine Power System and to see if the technology is electrically practical.

The works of the dynamic study were to evaluate the effects of operating the dragline on the

Cloudbreak power system carry out, dynamic performance analysis, determine system stability

and propose options for power system control. The study also evaluated the interconnection

of the Cloudbreak and Christmas Creek power stations, as this would be an effective solution

to potential high voltage connection issues of the dragline and also enhance the integrity of

both power systems.

4.2 MethodologyConsignment with DIgSILENT

From start to finish, the intern was on a consignment with DIgSILENT Pacific, which involved

the data collection, modelling and project management of the dynamic study. This

arrangement allowed the intern to communicate the project development during theexecution of the project between the FMGL Principal Electrical Engineer and DIgSILENT Pacific

project team, which consisted of one Principal Electrical Engineer and one Senior Electrical

Engineer. The intern met on a daily basis with the DIgSILENT Pacific project team and had a

workstation at their office.

Software

The steady state and dynamic modelling was done through the company owned software

DIgSILENT PowerFactory v14.0.523. The intern had previously used DIgSILENT PowerFactory

during his studies at University and was familiar with the power system software. The team at

DIgSILENT also provided on the job training during the course of the project to help familiarisethe intern with procedures that DIgSILENT practiced.

Building the Model and Input Data

The existing Cloudbreak power system PowerFactory model was modelled similar to the

system identified in Section 4.1, and the load data used in the model is relevant to the SCADA

Cloudbreak load demand information from 15/08/2011 - 17/08/2011, as attached in Appendix

B. In order to satisfy the load requirements of the dragline peak power magnitude of 28.6MW,

an additional six 2.42MW generators were connected to the Cloudbreak power station

switchboard. This results in 21 x 2.42MW peak generation capacity and three 2.42MW

generators not in service to satisfy the power station operating philosophy of (n+3). Buildingthe Cloudbreak model was a straightforward process, as the power system had already been

modelled in SKM PTW software, as mentioned in section 4.1, and all the necessary

documentation was available.

The 11kV Christmas Creek power system model includes 23 x 2.42MW peak generation

capacity and three 2.42MW generators not in service to satisfy the Christmas Creek power

station operating philosophy of (n+3). The current Christmas Creek peak load demand is

24.4MW and was obtained from the site load-demand list schedulefrom the site electrical

engineers. However the T155 expansion includes an additional future peak load of 27MW and

as a result this increases the total future maximum load demand to 51.4MW. A diversity factorof 0.9 was applied, resulting in a total future maximum load demand of 46.3MW.


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The intern was heavily involved in building the Christmas Creek Model. The data collection

process was quite extensive due to the fact that the Christmas Creek Mine only finished

construction in 2011, the as-built drawings were not documented, and the T155 expansion of

the mine was currently being implemented. This gave the intern an excellent opportunity to

work alongside the Christmas Creek principal electrical engineer in drafting up the entire

Christmas creek power system and incorporating the T155 expansion. The general Christmas

Creek power system layout is attached in Appendix I which outlines the generation,

distribution and load arrangements.

Flywheel

One of the power system control implementations used in the dynamic study was to utilize a

Flywheel Energy Storage System, which will allow peak shaving and further stability support

to the power system. The primary function of the FESS is to provide real and reactive power

support to a power system. Traditionally extra spinning reserve is the method used to handle

large cyclic loads. However this is quite an expensive approach (increased fuel consumption),

and in some cases diesel generator response to fluctuating loads does not occur in an

acceptable time period.

A flywheel energy storage system has the following benefits:

Smoothes out cyclic and transient loads Masks load fluctuations from the power supply Voltage compensation through reactive power injection Highly dynamic with response in 5 milliseconds from zero to nominal power Modular design with no limit to the number of units paralleled Very low harmonic content

The brand and model of the flywheel used in the dynamic study to provide power system

control was the PowerStore 1800. The construction of the flywheel is shown in Figure 2-2.

Figure 4-2 Construction of PowerStore Flywheel

Flywheels store mechanical energy which can be transferred to and from the flywheel by an

electrical machine (generator/motor) and power electronics. The kinetic energy stored in a

flywheel is proportional to the inertia and the rotational speed squared. The main components

of the flywheel include a power converter (AC-DC-AC), controller (control and SCADA system),

stator, bearing and a rotor. The flywheel unit rotates at a rated speed of 3600 rev/min anduses a pressurised helium environment to reduce frictional losses. The generator/motor is

driven by a variable speed drive converter that varies the voltage and frequency to control the


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power coming into or out of the flywheel. The complete flywheel energy storage system is

installed in an eighteen tonne 12000mm x 2480mm x 3330mm shipping container as shown

in Figure 2-3.

Figure 4-3 PowerStore Flywheel Substation Layout

The electrical details of the PowerStore 1800 flywheel is outlined in Table 2-17 below.

Table 4-2 PowerStore Flywheel Specification

PowerStore Flywheel Electrical Specification

Nominal Voltage Rating 380VAC 440VAC

Nominal Current Rating 2500A

Energy Storage (@ 3600rpm) 18MW.sec

Nominal Apparent Power Rating 1800kVA

Nominal Real Power Rating 1650kW

Nominal Reactive Power Rating 1800kvar

Power Conversion Efficiency >90% (charge or discharge)

Dragline

The electrical system within the dragline excavator comprises an installed capacity of 1.47MW.

There are 30 main motors (10 swing motors, 8 hoist motors, 8 drag motors and 4 propel

motors) which are distributed by 4 x 5MVA 22/0.9kV transformers and controlled on a 900VDC

interface including 42 IGBT inverters and 36 IGBT rectifiers. The converters allow power factor

control between 0.8 and 0.93 leading, however for the purposes of this dynamic study the

dragline power factor is set at 1.0 for all conditions.

Cooling System

Flywheel

Control System Inverters Transformer


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The intern was involved in calculating the total energy consumption and regeneration of the

dragline. This calculation would aid in both sizing and determining the number of flywheels

required to control the power load from the dragline. It also assisted in the dynamic modelling

of the dragline in the study. The intern firstly had to convert the dragline typical real power

versus time curve from the manufacturer to MSExcel. As this was the only source of

information and the manufacturer was unable to provide reasonable data on the curve, the

intern converted the information from the manufacturer specification to electronic data using

graphing software Digitizelt v1.5. This software scans the profile of the curve and a scaling

factor is then applied which produces the data points (x-time, y-real power) in an MSExcel

(.csv) format. The intern then applied the trapezoidal method to the data to calculate the

approximate area under the curve. The dragline MSExcel data, method and calculations are

attached in Appendix J.

The required number of flywheels was calculated based on peak shaving the energy

consumption of the dragline with magnitudes above 21MW (value decided by FMG Principal

Electrical Engineer). The calculations was done using the dragline model in MSExcel. The

MSExcel spreadsheet for flywheel calculation is attached in Appendix J.

The dragline is to be supplied by an OHL supply circuit incorporating 15 x 2km sections with 16

drop points. This power supply is distributed through a 20MVA 11/22kV step-up transformer

connected to the Cloudbreak power station. The purpose of this drop point arrangement is

because over time the dragline will move over a distance of 30km as it removes overburden

from various sections of the mine pit. At each drop point, power is supplied through a 2km

trailing cable to the dragline. This arrangement is covered in more detail later in this report.

Future Interconnection

As this is only a feasibility study, the interconnection between the two power stations was only

a simple 66kV design, that incorporated two 40MVA 11/66kV step-up transformers and a

40km (approximate distance between Cloudbreak and Christmas Creek) single circuit ACSR/GZ

Lemon as the phase conductors and a 24 fibre OPGW as the earth conductor. The

interconnection arrangement was decided through exploring three different possible options

that incorporated both redundancy and reliability. The three possible interconnection options

were the following:

1. One 40km 66kV single circuit with two 40MVA 11/66kV step-up transformersconnecting both 11kV power station switchboards.

2. Two 40km 66kV single circuits with two 40MVA 11/66kV step-up transformers percircuit connecting both 11kV power station switchboards.

3. Two 40km 66kV single circuits with one 40MVA 11/66kV step-up transformer (CC) andone 40MVA 22/66kV step-up transformer (CB) per circuit connecting a new 22kV

Cloudbreak switchboard (between the 11kV power station switchboard and SW411)

and the Christmas Creek 11kV power station switchboard.

Option 1 was selected for this study, as it was the simplest design and would be the cheapest

reliable arrangement.

Dynamic Models

The study assumed that the generators at both Cloudbreak and Christmas Creek are identical

in terms of machine and controller parameters. The total inertia of the engine, generator


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flywheel, rotor and coupling is 0.7s/MW. It is assumed that all generators at both Cloudbreak

and Christmas Creek operate less than 3% frequency droop. The dynamic and excitation model

was not available for the Cloudbreak and Christmas Creek engines; instead an appropriate

model was suggested, tested and used in the study.

The flywheel dynamic model was developed by DIgSILENT and used the following control

strategy and assumptions, which were discussed with a PowerCorp representative organised

by the intern. The interns dragline line energy modelling aided in this process.

Maximum import/export power of 1.65MW within 5ms. Grid converter has a rating of 1.8MVA. Capability of control output/input active power according to set points. Capability of performing voltage control. Rated at maximum 18MWs of storage energy. Identify the draglines peak consumption duration, utilising flywheel MW capacity to

supply the draglines peak demand.

Identify the regeneration duration of the dragline and utilise the flywheels capacity toconsume the regeneration energy.

MW utilisation of flywheel is the first priority, the remaining MVA capacity of the gridconverter side is used to stabilise the flywheels terminal voltage.

The state of charge set point is set at 80%, which is controlled by a slow outercontroller loop to compensate for the possible differences between the generation

and consumption cycle.

Test Criteria

To assess the voltage stability, the PV curve method was used to evaluate the voltage versus

power consumption at the dragline point of common coupling. This assessment provides an

estimation of the supply circuits power transfer capability. The power systems dynamic

behaviour was simulated over a 180 second period which is equivalent to three typical cycles

of the draglines operation as shown in Figure 2-1. The dynamic study was evaluated over

various operating scenarios and was assessed on the following limits:

+/-2% frequency deviation and +/-5% voltage variation at each of the power stations. -20/+10% voltage variation at the dragline connection to the trailing cable. Maintaining generators MVA loading below 85% rating.

The power loading at each power station is assumed to be at maximum demand to model the

worst case scenario for each case study.


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Case Studies

The system arrangement for each case study is outlined in Table 2-18.

Table 4-3 Dynamic Study details of Case Studies

Study

Case

#Cloudbreak

Genset

#Christmas

Creek Genset

66kV

Interconnection

Dragline

Supply

#Flywheel

1 15 N/A No 22kV single

circuit

0

2A 21 N/A No 22kV double

circuit

0

2B 21 N/A No 22kV double

circuit

5

2C 21 23 Yes 22kV double

circuit

5

3A 21 23 Yes 66kV single

circuit

0

3B 21 23 Yes 66kV single

circuit

0

In regards to dragline supply connection the following four arrangements were used for the

respective case study and are shown in Appendix K.

22kV single circuit 1

This 22kV supply option, a 20MVA 11/22kV transformer is connected to Cloud Break power

station 11kV switchboard to supply a 30km dragline single supply circuit. The cable selected for

this circuit is a single ACSR Phosphorus phase conductor from the OLEX catalogue.

22kV double circuit 2A

The 22kV dragline supply connection for 2A is the same as case study 1, however two 30km

dragline supply circuits are modelled between the Cloud Break power station 11kV

switchboard and the dragline.

22kV double circuit with flywheel power control system 2B

The 22kV dragline supply connection for 2B is the same as case study 2A however the flywheel

power control system which consists of five parallel flywheels as specified in this report is

connected at drop point 11.

22kV double circuit with interconnection and flywheel power control system 2CThe 22kV dragline supply connection for 2C is the same as case study 2B however the 66kV

interconnection as specified earlier between the Cloudbreak and Christmas Creek power

station is used in this case study.

66kV single circuit with interconnection 3A/3B

For the 66kV supply option, the 66kV 30km dragline supply circuit is connected to the

Cloudbreak side interconnection gantry. A 20MVA 66/22kV transformer is apparent between

the 66kV dragline single supply circuit and the dragline. The cables selected for this circuit are

single ACSR Grape phase conductors from the OLEX catalogue.


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4.3 ResultsThe results examine the effect of transient disturbances from the dragline on the power

system. The objective was to determine whether or not the power system would return to

synchronous frequency, sustain acceptable voltage levels and generator loading after

experiencing a transient disturbance produced by the dragline. PowerFactory dynamic

simulation results for all case studies are attached in Appendix L.

Case Study 1

The effect of the dragline operation was performed on the existing Cloudbreak power system:

the power system was unable to supply the required 28.6MW peak load. As seen in figure 2-4

the dragline PCC voltage falls below 0.80pu at 16.086MW (dragline first power consumption

peak), which, as a result fails, the testing criteria of acceptable voltage limits during dragline

operation. As seen in Appendix K for case study 1, the Cloudbreak generators fail to supply the

power system demand at 4 seconds, which, as a result, the synchronous frequency decays to

zero and the power station voltage decreases to 0.20pu, which is unacceptable.

Figure 4-4 Case Study 1 Dragline Voltage (p.u) vs. Real Power Consumption (MW)

Case Study 2A

As seen in Figure 2-5 the expanded Cloudbreak power station of 21 generators is unable to

supply the required power to the dragline at an acceptable voltage. The dragline PCC voltage

reaches 0.80pu at only 26.221MW, which again fails the testing criteria of acceptable voltage

limits during dragline operation. As seen in Appendix K for case study 2A, the Cloudbreak

generators exceed the 80% loading criteria by approximately 115% of test criteria and the

synchronous frequency falls just below 0.98pu which is unacceptable. The results are outlined

in Table 2-19.


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Table 4-4 Dragline Dynamic Case Study 2A Results

Minimum

Fluctuation

Maximum

Fluctuation

Test Criteria

Limits

Acceptability

Power Station

Voltage (p.u)

0.61 1.08 0.95 1.05 Fail

Power Station

Frequency (p.u)

0.978 1.016 0.98 1.02 Fail

Power Station

Loading (p.u)

0.30 1.15


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Table 4-6 Dragline Dynamic Case Study 2B Results

Minimum

Fluctuation

Maximum

Fluctuation

Test Criteria

Limits

Acceptability

Power Station

Voltage (p.u)

1.017 1.041 0.95 1.05 Pass

Power Station

Frequency (p.u)

0.983 1.010 0.98 1.02 Pass

Power Station

Loading (p.u)

0.33 0.76


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Table 4-7 Dragline Dynamic Case Study 2C Results

Minimum

Fluctuation

Maximum

Fluctuation

Test Criteria

Limits

Acceptability

CB Power Station

Voltage (p.u)

1.022 1.039

0.95 1.05

Pass

CC Power Station

Voltage (p.u)

1.030 1.037 Pass

CB Power Station

Frequency (p.u)

0.990 1.005

0.98 1.02

Pass

CC Power Station

Frequency (p.u)

0.990 1.005 Pass

CB Power Station

Loading (p.u)

0.39 0.64


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due to the relatively large distance between Christmas Creek and the PCC of the dragline. Also,

case studies 3A and 3B are modelled to understand the best generator dispatch strategy

between the two power stations in regards to voltage regulation and generator loading.

Case Study 3A

Case Study 3A was modelled using no loa

final report

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