ELEC5205 High Voltage Engineering
The Complete Exam Bible · S2 2026ELEC5205 Overview
- Semester 2 2026
- Postgraduate
- Closed-book final exam
- Camperdown/Darlington
Failure physics and equipment decisions
High Voltage Engineering begins with the microscopic events that turn an insulating gas into a conducting path. Electron energy, collision distance, ionisation and attachment determine avalanche growth.
- Start with the field Geometry decides where ionisation, heating or dielectric stress concentrates.
- Read evidence cautiously Calibrated pulses, gases and ageing products support diagnoses with explicit limits.
- Calculate the duty Line, cable and breaker choices follow stated electrical and thermal constraints.
What you get in the full ELEC5205 Exam Bible
- 12 chapters, 50 pages — every examinable topic
- 30 original practice questions, each with a model answer in the Final exam format
- 12 worked examples, solved the way ELEC5205 marks
- 15 computed figures, redrawn from the course’s own numbers
- Exam-morning plan for the Final exam (40%) — what to revise last, where marks are lost
Free on this page: assessment table, chapter map, one worked example, key terms, FAQ. The rest is in the full exam bible.
How ELEC5205 is assessed
| Component | Weight | Format |
|---|---|---|
| Laboratory | 30% | Three group laboratory reports, 10% each |
| Assignment | 20% | Individual project on a high-voltage engineering application |
| Mid-semester test | 10% | Closed book, one hour, scheduled in Week 7 on modules M1 through M5 |
| Final exam | 40% | Closed book, 2.5 hours, cumulative across every module |
The published weights total 100%. No separate attendance condition was identified in the reviewed assessment evidence. Pass eligibility requires a final-examination result of at least 35%.
Assessment structure
Laboratory, assignment, mid-semester test and final exam weights total 100%.
What other students are asking about ELEC5205
- Where can I find lecture notes or study guides for ELEC5205 at USyd?
- The ELEC5205 study guide in AskSia Library covers High Voltage Engineering in 12 chapters, with the assessment table, a chapter-by-chapter topic map, key terms and a worked example, free to read on this page.
- Is there a final exam in ELEC5205, and how much is it worth?
- Yes. In the offering this AskSia Library guide is built from, Final exam carries 40% of the ELEC5205 mark; the full split is Laboratory 30%, Assignment 20%, Mid-semester test 10%, Final exam 40%.
- What does ELEC5205 cover on nonuniform fields, pressure and vacuum?
- In AskSia Library's ELEC5205 guide, the Nonuniform Fields, Pressure and Vacuum chapter explains compare spatial ionisation growth with surface-controlled breakdown regimes.
- What does ELEC5205 cover on corona and stepped breakdown?
- In AskSia Library's ELEC5205 guide, the Corona and Stepped Breakdown chapter explains track local inception, space-charge feedback and propagating leaders.
- What does ELEC5205 cover on solid, liquid and surface breakdown?
- In AskSia Library's ELEC5205 guide, the Solid, Liquid and Surface Breakdown chapter explains distinguish treeing, tracking and flashover by path and timescale.
What ELEC5205 covers
Twelve source-led chapters move from discharge physics through diagnostics, transmission equipment, protection and commissioning.
Gas Avalanche and Paschen Law
Relate electron multiplication, streamer formation and pressure-distance scalingFrom collision to conducting channel
Gas breakdown begins when free electrons gain enough energy between collisions to ionise molecules.
- Effective Ionisation
- Avalanche Growth
- Streamer Criterion
- Paschen Law
- Pressure-Distance Boundary
- Uniform-Field Assumption
Nonuniform Fields, Pressure and Vacuum
Compare spatial ionisation growth with surface-controlled breakdown regimesThree regimes, three controlling questions
A nonuniform gap requires integration of the local effective ionisation coefficient because field varies along the electron path.
- Nonuniform Integral
- Coaxial Field
- Quasi-Uniform Gap
- Electrode Conditioning
- Compressed Gas
- Vacuum Breakdown
Corona and Stepped Breakdown
Track local inception, space-charge feedback and propagating leadersLocal activity before full breakdown
Corona occupies the extreme-field region near sharp hardware and can persist below whole-gap breakdown voltage.
- Corona Inception
- Streamer Zone
- Space-Charge Feedback
- Trichel Pulses
- Stepped Leader
- Lightning Protection
Solid, Liquid and Surface Breakdown
Distinguish treeing, tracking and flashover by path and timescaleLocation decides the failure label
Real solid insulation contains voids, droplets, particles and electrode irregularities that concentrate field and initiate local heating or discharge.
- Electrical Treeing
- Water Trees
- Liquid Recovery
- Surface Tracking
- Dry-Band Arcing
- Flashover
Insulation Design for HV Equipment
Connect field grading to cables, bushings and outdoor insulationDesign features answer known failure modes
Semiconductive cable screens smooth the field at stranded conductors, oil-paper processing removes voids, and XLPE reduces capacitance and dielectric loss.
- Cable Screens
- Oil-Paper Insulation
- XLPE Cable
- Bushing Foils
- Creepage Paths
- Insulator Grading
AC, DC and Impulse Test Sources
Select cascaded, resonant, multiplier and impulse arrangementsWaveform selects the source
High-voltage tests investigate service withstand, design performance or ultimate strength.
- Cascaded Transformers
- Series Resonance
- Voltage Doubler
- DC Multiplier
- Impulse Shaping
- Marx Generator
Partial Discharge Measurement
Calibrate apparent charge and interpret phase-resolved pulse evidenceMeasure an equivalent terminal effect
Partial discharge is local activity that does not bridge the full insulation path.
- Apparent Charge
- Calibration Pulse
- Coupling Network
- Phase Pattern
- UHF Detection
- Acoustic Location
Transformer Condition Monitoring
Combine dissolved gases, furfural trends and sampling uncertaintyInterpret trend and mixture together
Dissolved gas analysis measures products created when electrical or thermal faults decompose transformer oil and paper.
- Dissolved Gas Analysis
- Fault Gas Pattern
- Furfural
- Cellulose Ageing
- Sampling Error
- Trend Diagnosis
Overhead Line Parameters and Surges
Convert conductor geometry into parameters, ratings and wave behaviourCompress geometry without losing meaning
Geometric mean distance represents phase spacing, while geometric mean radius represents conductor or bundle construction.
- Geometric Mean Distance
- Self-GMR
- Line Inductance
- Line Capacitance
- Surge Impedance
- Wave Reflection
Underground Cable Design
Size insulation and test charging, loss and thermal constraintsSeveral limits compete for one design
Coaxial cable geometry produces high capacitance, low inductance and low surge impedance compared with an overhead line.
- Radial Electric Field
- Insulation Thickness
- Cable Capacitance
- Charging Current
- Dielectric Loss
- Thermal Grouping
Switchgear, Fuses and Breaker Ratings
Compare interruption media and calculate network fault dutiesInterruption technology and rating are separate decisions
Air, oil, vacuum and SF6 breakers differ in arc control, voltage application, maintenance, safety and environmental burden.
- Breaker Media
- Fault MVA
- Symmetrical Current
- Peak Duty
- Fuse Melting
- Arc Interruption
Testing, Commissioning and Standards
Build a staged assurance chain from specification to energisationAssurance begins before the equipment arrives
A fit-for-purpose specification defines service conditions, standards and acceptance evidence.
- Fit-for-Purpose Specification
- Factory Inspection
- Routine Test
- Site Test
- Commissioning Hold Point
- Standards Selection
Space charge and photoionisation can transform a large avalanche into a streamer, while pressure, electrode shape and surface condition decide whether a uniform-gap model remains useful.
The guide then contrasts corona, solid and liquid treeing, surface tracking and flashover so that a visible discharge is not automatically mislabelled as complete breakdown.
Testing and condition evidence
The middle chapters connect dielectric behaviour to practical sources and measurements.
Cascaded transformers, resonant testers, voltage multipliers and impulse generators create different waveforms for different insulation questions. Partial-discharge measurement uses calibrated apparent charge and phase patterns rather than claiming direct access to a hidden defect. Transformer monitoring combines dissolved gas mixtures with furfural evidence and sampling uncertainty.
The recurring method is to state what was measured, which mechanism it supports and what additional observation would distinguish a plausible alternative.
Lines, cables and interruption
The final technical block turns geometry into overhead-line inductance, capacitance and surge impedance, then contrasts that behaviour with coaxial underground cables.
Cable insulation thickness, charging current, dielectric loss and thermal grouping impose separate constraints. Switchgear chapters distinguish breaker technology from breaker rating, add grid, generator and motor fault contributions, and connect fuse melting to the following arc interval.
The closing chapter treats specification, factory inspection, site testing and commissioning as successive evidence gates rather than one final event.
Pass condition in the reviewed material
No separate attendance condition was identified in the reviewed assessment evidence. Pass eligibility requires a final-examination result of at least 35%.
Track that examination condition separately from the overall weighted total.
How to revise
Redraw each chapter figure, rebuild the original worked example with its numbers covered, and complete the changed-condition practice. Always state the physical regime before selecting an equation. Keep units, voltage basis, rms or peak convention and time regime visible.
Finish calculations with the engineering consequence, then test whether the conclusion survives a change in geometry, material, environment or operating condition.
Worked example · free
Check a cable charging-current limit
- 2Calculate length from allowed current divided by current per kilometre.
- 2Report the result with units and a sensible precision.
- 2Name another constraint that still needs checking.
Key terms
- Apparent Charge
- Apparent Charge is the calibrated terminal charge that would reproduce the measured voltage change of a partial-discharge event.
- Avalanche
- Avalanche is the multiplying population of electrons created when ionising collisions outpace attachment in a gas.
- Corona
- Corona is a local partial breakdown sustained in a region of extreme electric field without bridging the full gap.
- Creepage Distance
- Creepage Distance is the surface path between conductors that an external discharge would have to follow.
- Dielectric Loss
- Dielectric Loss is the real power dissipated as polarisation and leakage processes cycle within insulation.
- Dissolved Gas Analysis
- Dissolved Gas Analysis interprets fault-related gases in transformer oil as evidence of discharge, heating or arcing.
- Geometric Mean Distance
- Geometric Mean Distance is the effective spacing used to represent a multi-conductor line geometry in parameter calculations.
- Geometric Mean Radius
- Geometric Mean Radius is the effective conductor or bundle radius used in inductance calculations.
- Paschen Law
- Paschen Law relates uniform-gap breakdown voltage to the pressure-distance product within its valid regime.
- Streamer
- Streamer is a conducting ionised channel formed when avalanche space charge and photoionisation create rapid secondary growth.
- Tracking
- Tracking is progressive carbonised surface damage produced by leakage current, dry-band arcing and repeated local discharge.
- Treeing
- Treeing is the growth of branching discharge channels through bulk solid or liquid insulation under concentrated stress.
ELEC5205 FAQ
What makes gas insulation break down?
Free electrons gain energy from the electric field and create further electrons through ionising collisions. When net ionisation produces a sufficiently large avalanche, space charge and photoionisation can form a streamer and a conducting path. Pressure, gap length and electrode geometry decide whether the uniform-field model applies.
How is corona different from complete breakdown?
Corona is confined to a high-field region near an electrode or hardware feature and may remain stable through space-charge feedback. Complete breakdown bridges the insulation path and collapses its impedance. A visible or measured local discharge therefore does not automatically mean the whole gap has failed.
Why is partial discharge measured in apparent charge?
The true charge movement at a hidden defect cannot be measured directly at the equipment terminals. Calibration defines the terminal-injected charge that would create the same voltage response. This apparent charge is comparable and useful, but it must not be described as the microscopic defect charge.
What do dissolved gases reveal about a transformer?
The relative gas pattern supports hypotheses about low-energy discharge, oil or paper overheating and high-energy arcing. Trend, sample handling and operating history matter alongside the mixture. Gas evidence can suggest a fault class, but location and severity usually need complementary electrical, thermal or inspection evidence.
Which calculations matter most for lines and cables?
Overhead lines use conductor geometry to calculate GMD, GMR, inductance, capacitance and surge impedance. Underground cables add radial electric field, insulation thickness, charging current, dielectric loss and thermal constraints. Keep physical radius separate from self-GMR and use the voltage basis required by each formula.
What assessment and pass conditions apply?
The current structure uses laboratory reports, an individual project, a mid-semester test and a cumulative final examination. Their published weights total the unit mark. No separate attendance condition was identified in the reviewed assessment evidence. Pass eligibility requires a final-examination result of at least 35%, so aggregate marks and the examination condition must both be tracked.
What is known about the final examination?
The current schedule states that it is a 2.5-hour closed-book examination cumulative across lecture, laboratory, tutorial and assignment material. It does not specify a final-paper question count in the available files, so use current Canvas instructions for calculator, formula-sheet and detailed format information.
Questions students ask in each ELEC5205 chapter
- Why does avalanche size grow exponentially?
- Each ionising electron can create additional electrons that undergo the same process, so the growth rate is proportional to the population already present. Integrating that proportional rate over distance produces an exponential rather than a linear relation. Chapter 01 · Gas Avalanche and Paschen Law
- Why does compressed gas expose electrode defects?
- High pressure can make the ideal bulk-gas prediction very strong, so local field enhancement and electron emission from microscopic hills or particles become comparatively important. Many starting electrons can reach streamer size with less avalanche gain. Chapter 02 · Nonuniform Fields, Pressure and Vacuum
- Why does corona not always become a spark?
- Space charge can lower the field near the initiating electrode after a burst, suppressing further streamer growth. The active high-field region may also be too short for streamers to cross the weak-field remainder of the gap. Chapter 03 · Corona and Stepped Breakdown
- Where do electrical trees begin?
- They can begin at gas voids, conductive particles, water droplets or microscopic electrode protuberances where the local field is enhanced. Heating, bond breaking and electrostatic forces extend the initial damage into branching hollow channels. Chapter 04 · Solid, Liquid and Surface Breakdown
- Why do XLPE cables use semiconductive screens?
- A stranded conductor has microscopic and macroscopic irregularities that would concentrate electric field in the polymer. A bonded carbon-loaded layer forms a smoother equipotential surface and reduces local stress that could initiate void discharge or treeing. Chapter 05 · Insulation Design for HV Equipment
- Why is resonance useful for testing cables?
- A long cable is strongly capacitive. Tuning a reactor against that capacitance produces a high test voltage while the supply covers mainly losses, so required source power is far below the reactive power circulating in the test circuit. Chapter 06 · AC, DC and Impulse Test Sources
- Why is calibration required for partial-discharge measurement?
- The measuring circuit, filter, amplifier and test-object capacitance transform the fast discharge pulse. A known injected charge establishes the relationship between displayed response and apparent charge for that exact measurement chain. Chapter 07 · Partial Discharge Measurement
- Why are gas proportions useful?
- Different electrical and thermal energies favour different decomposition products, so the relative mixture carries mechanism information. Absolute concentration still matters because a stable proportion with rapidly rising total gas can indicate increasing activity. Chapter 08 · Transformer Condition Monitoring
- Why do inductance and capacitance use different radii?
- Inductance includes internal magnetic flux and therefore uses the conductor self-GMR. Capacitance follows the external electric field and uses physical conductor radius because electric field is zero inside the conductor. Chapter 09 · Overhead Line Parameters and Surges
- Why can charging current limit cable length?
- Cable capacitance draws reactive current even when little real load is delivered. Because current grows with voltage, frequency, capacitance and length, a long AC cable can consume an unacceptable fraction of conductor rating. Chapter 10 · Underground Cable Design
- Why do motors contribute to a fault?
- Stored rotational energy keeps the machines turning immediately after bus voltage collapses. For the first cycles they behave as generators and feed current back into the fault through their subtransient reactance. Chapter 11 · Switchgear, Fuses and Breaker Ratings
- Why are factory tests not enough?
- Transport and installation can introduce damage or incorrect connections, while earthing, phasing, protection and interlocks only exist as an integrated site system. Site and commissioning evidence therefore answer questions that factory records cannot. Chapter 12 · Testing, Commissioning and Standards
How to study for the exam
Begin each revision session with one mechanism sketch: avalanche growth, corona zones, a cable radial field, a PD calibration loop or a travelling-wave junction. Rebuild the associated equation from definitions and check units before calculating. Then complete one original changed-condition problem and write the physical consequence in a final sentence.
Alternate early insulation chapters with later equipment chapters so that field concentration remains connected to the design feature that controls it. For the cumulative final, practise closed-book retrieval of formulas and symbol meanings, but do not treat the formula sheet as a decision engine.
Finish each week by recording one error in regime selection, one unit or voltage-basis error, and one interpretation that overclaimed the evidence. Rework those errors after a delay. Before the exam, confirm current operational instructions on Canvas and keep the published pass condition separate from the overall weighted mark.
Your AI Electrical Engineering tutor for ELEC5205
Stuck on a hard ELEC5205 question? Sia is AskSia’s AI Electrical Engineering tutor — ask any ELEC5205 High Voltage Engineering question and get a clear, step-by-step explanation grounded in how the course is actually taught and assessed. Read this whole study guide free, then take your hardest questions to Sia.
