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Power System AnalysisELEC4612
Toan Phung
The University of New South Wales
School of Electrical Engineeringand Telecommunications
COURSE OUTLINES
Course information: context, aims
Learning outcomes
Teaching strategies: lectures, labs, tutorials.
Assessment details: tests, labs, exam
Schedule: tentative timetable
Resources: books, references
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Course staff:
Convener:
Dr. Toan Phung
Room EE107
Email: [email protected]
Consultation: Tues 14-15, Thurs14-15
Credit: 6 UOC, 10-12 hours/week workload
Contact hours:
Lectures: 2 hrs/wk
Tutorials: 1 hr/fortnight
Labs: 3 hrs/fortnight
Course information Context:
Power systems = complex networks of generators and loads interconnected via transmission lines and various components (transformers, switchgear, etc).
Proper operation of a power system involves understanding the behavior of its components under steady state, dynamic and transient conditions, in order to be able to evaluate the response of this complex system to variation of loads, and to determine how this system can be controlled to supply the loads reliably.
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Eraring power station
23kV/776MVA Turbo-generator
150MVA 220/66/11kV power transformerSPI PowerNet (Victoria)
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132kV circuit breakers - West Liverpool substation – Endeavour Energy
330kV cable - Picnic Point to HayMarket - MetroGrid Project - TransGrid
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[Ref. TransGrid Annual Report 2007]
HV transmission lines
Course information
Aims:
To provide essential knowledge in mathematical techniques to analyze power systems. Two primary aims:
Steady-state analysis of power flow in power system networks.
Analysis of short-circuit faults in power system networks.
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Course informationTopics:
Basic concepts in power system analysis: phasors, complex power, 3-phase systems and per-unit
Equivalent circuit models for power system components transformers, generators, transmission lines and loads
Application of network matrices techniques and power flow analysis to study steady-state and dynamic behavior
Fault calculations: symmetrical components, symmetrical faults,and unsymmetrical faults
Power system transients, surge propagationPower system stability by use of swing equation, and a multi-machine system
Power system control and economic dispatch.
Learning outcomes:
Model major types of components used in electrical power systems
Analyze different types of short-circuit faults and over-voltage transients.
Calculate steady-state power flow in a power system.
Understand the power system dynamics and its stability.
Determine the economic dispatch in a power system.
Understand the power system control and protection
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Ref: TransGrid Annual Report 2008
TransGrid Control Room
Learning and teaching methods
Lectures
Laboratories
Tutorials
Homework
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Assessment:
Mid-session test: 15%
Labs: 15% (oral, written report, prac. test)
Tutorials: no marks
Final exam: 70%
Tentative schedule:
20/7/12
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Resources: Textbooks:
J.D. Glover, and M.S Sarma, T.J. Overbye, Power System Analysis and Design, 5th Edition (SI).
Lecture notes
Course website: check weekly for latest announcements
https://subjects.ee.unsw.edu.au/elec4612/
Reference books:
Electricity Networks
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Australia’s electricity generation (2010)
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Electricity Networks in NSW
Generation: Macquarie Generation, Delta Electricity, Eraring Energy, etc
Transmission: TransGrid
Distribution: AusGrid, Endeavour Energy, Essential Energy
Snowy Mountains Hydro Electric Authority operate some transmission lines in NSW
Electricity Networks in NSW - Generation
18,000 MW of installed generation capacity
Interconnectors with Queensland and Victoria provide additional 1100 MW and 1500 MW
fuel sources: black coal, natural gas, coal seam methane gas and renewable energy sources (hydro, wind, biomass, solar)
20,000 MW of power plant proposals (include >9000 MW from renewable sources)
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Peak winter demand:14,274 MW on 28/7/08
Peak summer demand:14,106 MW on 6/2/09
Ref: TransGrid Annual Report 2009
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http://www.industry.nsw.gov.au/energy
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12,600 km overhead transmission lines + underground cables91 substations and switching stations72 connection points to generators6 interconnectors to Victoria and Queensland354 distributor and direct customer connection points
Ref: TransGrid Annual Report 2011
2011:
74,889 GWh
98.99% availability
2.24 system minutes lostor 99.996% reliability
Electricity distributors for NSW
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EnergyAustralia
Electricity distributor for Sydney, Central Coast and Hunter regions of NSW
Distributes ~ 25,000 GWh of electricity annually, to 1.4 million customers through: More than 1000km of above ground 132kV HV cable Almost 500km of underground 132kV HV cable More than 400km of 66kV cables. More than 2200km of 33kV cables.
Integral Energy
network area covers Sydney’s Greater West, the Southern Highlands and the Illawarra.
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Distributed generation
Ref: N. Mohan
Power World Simulator
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Background
PowerWorld Simulator: an interactive software package for power system simulation, analysis and visualization
http://www.powerworld.com
Accompanies Glover & Sarma textbook
Developed at University of Illinois (version 1 in 1994), and commercialized in 1996
Can analyze large power systems (up to 100,000 buses)
Widely used in the power industry and utilities
Download PowerWorld Evaluation/Education version 16, including help files
Main Applications
Power Flow Analysis
Faults Analysis
Transient Stability (TS)
Contingency Analysis
Available Transfer Capability (ATC) Analysis
Optimal Power Flow (OPF)
Voltage Adequacy & Stability Tool (PVQV)
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OBJECTS Used in Modeling
Transmission lines, AC/DC lines Buses Generators Loads Transformers Switched shunts (capacitors or reactors) Series capacitors Areas, zones, substations, interfaces Fields (for showing values for each object) Line flow gauges, voltage gauges
Helps on using PW simulator
Installing and getting started
Using one-line diagrams
Creating, loading, and saving simulator cases
Building a one-line diagram
Edit Mode: Tools & Options
Properties of one-line display objects
Solving and simulating a case
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Working with PW Simulator
Install
Double click on PW icon
Now need a model of power system
Either: build a new case (model)
Or start an existing case: select a file, open case
Display look like following Figure
Example 1.1 (Textbook)
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Model and analysis of two bus system Drawing full schematic in 3 ph. excessively complicated
In normal operation 3 ph. systems are balanced. This permits system modeled as an equivalent 1 ph. system.
PW simulator use this approach
Nodes at which two or more devices join are called buses, represented by thick lines
Generators shown as a circle with “dog-bone” rotor
Large arrows represent loads
Transmission lines simply drawn as lines
connections between devices with single line joining system devices, hence the term “one-line diagram”
Bus voltage displayed in kV next to it
Power flow: visualized by arrows superimposed on lines, size and speed of arrows indicate direction and rate of flow.
Model and analysis of two bus system By “speed” mean PW simulator animate power systems
Animation starts with selecting Run Mode then selecting Solve (in Power Flow Tools)
Example 1.1 represents a simple power system in which a generator supplies power to a load through a 16 kV distribution system feeder
Solid square blocks on the line represent circuit breakers (C/Bs)
To open a C/B, position mouse over it and click
Clicking on any of C/Bs isolates load from generator and result in blackout
To vary load, click on up/down arrows between load value & “MW” field.
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Model and analysis of two bus system Additional information on most elements on one-line shown
by right-clicking on them
Right-click on generator symbol: open a local menu of additional information about generator
And so on. Meaning of some of these fields become clearer as we progress in the course
To modify display itself, right-click on a blank area of one-line → local menu opens,
Select one-line display options to display one-line display options dialog: you can customize many of display features such as colors
To retain changes before exiting PW simulator, click PW globe, select Save Case As and enter a different file name
The model stored in a *.pwb file (PW binary file)
One-line information stored in a *.pwd file (PW display file)
PW Simulator Edit Mode Run Mode: used for running simulations and performing
analysis
Edit Mode: used to modify existing cases or build new cases
Click on Edit Mode button to switch to edit mode
Then the main display changes slightly. One-line has a superimposed grid to help with alignment.
Adding a bus, done by selecting Draw, Insert, Bus
and moving mouse to desired one-line location
& clicking, the Bus options dialog appears
This dialog used to set bus parameters
As shown next =>
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Power Flow – Why important ?
Generation supplies load demand plus losses.
Bus voltage magnitudes are close to rated values.
Generators operate within specified real and reactive power limits.
Transmission lines and transformers are not overloaded.
Also known as Load Flow Problem.
Is fundamental in the study of power systems.
Successful power system operation under steady-state conditions requires:
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Power Flow – Why important ?
Power flow program is the tool for investigating these requirements. It computes voltage magnitude and angle at each bus.
As a by-product, real and reactive power flows and power losses in the network (transmission lines, transformers) can also be computed.
Power Flow Problem
For a balanced system, power flow is numerically the same for each phase
Therefore single phase model employed
Formulation start from nodal equation of an electric circuit I=YV
However, conventional nodal (or loop) analysis is not suitable for power flow study because:
Input data for loads normally given in terms of power, not impedance.
Generators are considered as power sources, not voltage or current sources.
Need to solve simultaneous non-linear equations.
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Solution Methods for Power Flow Equations
To solve these nonlinear equations require iterative numerical techniques
Among them two are employed to solve power flow problem:
Gauss-Seidel Iterative Method
Newton-Raphson Method
These will be introduced later in the course
They can be compared regarding their rate of convergence
Finally in terms of node voltages, active and reactive power at buses (supplied or consumed) can be obtained.
Per Unit Calculations
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Simplify calculations of power system quantities.
Express voltage, current, power and impedance as per unit values of selected base values of those quantities:
Specify 2 bases, usually VB and SB. Then:
Normally, VB taken as the rated system voltage
SB arbitrarily specified (100, 10, 1 MVA) or use rating of a major element in system (transformer, generator).
Also ratio of voltage bases on two sides of transformer must be the same as ratio of its voltage ratings.
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For balanced symmetrical 3-phase systems, do calculation on a single phase basis.
Careful when calculate appropriate base values of current and impedance. For Y-connected systems:
where VB and SB are the line voltage and 3-phase apparent power
To change per unit impedances from one base value to another:
impedances of transformers, generators, motors usually given on name plates in per unit based on the equipment’s rated voltage and power levels.
for cables, overhead lines, busbars, impedances most likely given in ohmic values.
