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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 2-19 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 2-22 Dragline Dynamic Case Study 3A Results ............................................................... 39
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
SW451 22.000 97.1 Acceptable
SW435 22.000 97.2 Acceptable
SW431 22.000 96.1 Acceptable
SW426 22.000 96.1 Acceptable
SW421 22.000 96.0 Acceptable
MC454 0.400 100.3 Acceptable
SW455 0.690 100.8 Acceptable
SW456 0.690 101.1 Acceptable
MC451 0.400 99.6 Acceptable
SW452 0.690 97.9 Acceptable
MC435 0.400 98.4 Acceptable
SW433 0.690 99.9 Acceptable
CSI-HPGR 22.000 95.9 Acceptable
TX02_LV 0.400 95.9 Acceptable
TX03_LV 0.400 95.9 Acceptable
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TX04_LV 0.400 95.9 Acceptable
MC431 0.400 97.8 Acceptable
SW432 0.690 98.7 Acceptable
SW437 () 0.690 99.3 Acceptable
SW437 (Y) 0.690 99.3 Acceptable
SW442 0.690 99.2 Acceptable
MC426 0.400 98.7 Acceptable
SW427 () 0.690 99.5 Acceptable
SW427 (Y) 0.690 99.5 Acceptable
MC428 0.400 98.8 Acceptable
SW429 () 0.690 98.7 Acceptable
SW429 (Y) 0.690 98.7 Acceptable
MC430 0.400 98.9 Acceptable
SW439 () 0.690 99.6 Acceptable
SW439 (Y) 0.690 99.8 Acceptable
SW714 0.400 98.2 Acceptable
MC421 0.400 98.8 Acceptable
MC422 0.400 98.4 Acceptable
SW423 () 0.690 97.3 Acceptable
SW423 (Y) 0.690 97.3 Acceptable
CAMP 11.000 97.3 Acceptable
SB-731 0.400 107.8 *Acceptable
SB-732 0.400 106.7 *Acceptable
MC441 0.400 97.5 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
SW454 22.000 97.0 Acceptable
SW451 22.000 97.0 Acceptable
SW435 22.000 97.0 Acceptable
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SW431 22.000 97.2 Acceptable
SW426 22.000 97.2 Acceptable
SW421 22.000 97.2 Acceptable
SW505** 22.000 97.0 Acceptable
TF505A/B/C** 0.690 97.6 Acceptable
SW506** 0.690 97.3 Acceptable
MC-507** 0.400 98.7 Acceptable
MC-508** 0.400 98.9 Acceptable
MC454 0.400 100.1 Acceptable
SW455 0.690 100.6 Acceptable
SW456 0.690 100.9 Acceptable
MC451 0.400 99.5 Acceptable
SW452 0.690 97.7 Acceptable
MC435 0.400 98.2 Acceptable
SW433 0.690 99.7 Acceptable
CSI-HPGR 22.000 95.8 Acceptable
TX02_LV 0.400 95.8 Acceptable
TX03_LV 0.400 95.8 Acceptable
TX04_LV 0.400 95.8 Acceptable
MC431 0.400 99.0 Acceptable
SW432 0.690 100.0 Acceptable
SW437 () 0.690 100.5 Acceptable
SW437 (Y) 0.690 100.5 Acceptable
SW442 0.690 100.5 Acceptable
SW440** 0.690 99.4 Acceptable
MC426 0.400 100.1 Acceptable
SW427 () 0.690 100.2 Acceptable
SW427 (Y) 0.690 100.7 Acceptable
MC428 0.400 99.0 Acceptable
SW429 () 0.690 100.7 Acceptable
SW429 (Y) 0.690 100.7 Acceptable
MC430 0.400 99.8 Acceptable
SW439 () 0.690 99.3 Acceptable
SW439 (Y) 0.690 99.1 Acceptable
SW714 0.400 99.4 Acceptable
SW443 ()** 0.690 100.4 Acceptable
SW443 (Y)** 0.690 100.5 Acceptable
MC421 0.400 100.0 Acceptable
MC422 0.400 99.7 Acceptable
SW423 0.690 98.6 Acceptable
SW423 0.690 98.5 Acceptable
CAMP 11.000 97.3 Acceptable
SB-731 0.400 107.8 *Acceptable
SB-732 0.400 106.7 *Acceptable
MC441 0.400 97.4 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
MC426 46.8 105.9 45.9 50kA 1s 105kA Unacceptable
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
MC422 48.5 109.3 44.1 50kA 1s 105kA Unacceptable
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)
MC422 (104.1% 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)
MC421 (94.6% of the peak rating)
MC428 (94.4% of the peak rating)
MC430 (96.2% of the peak rating)
MC451 (96.4% of the peak 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
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