ECE3051 - Electrical Energy Systems
Introduction to Power Systems
Dr. Reza Razzaghi
Department of Electrical and Computer Systems Engineering
Monash University
Clayton, Victoria
Objectives of ECE3051
❖ Overview of fundamental elements in power networks and their equivalent models.
❖ Analysis of magnetic elements including power transformers, induction and synchronous
machines.
❖ Analysis of power electronic converters.
❖ Power transmission lines and fundamentals of power flow in power lines.
❖ Short circuit analysis and power system protection.
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Introduction to Power Systems
Learning Outcomes of Week 1
1. Introduction to Power Systems
➢
➢
Describe power system structure, from generation to distribution.
Reflect on the new challenges in power networks and potential solutions
2. Single Phase AC Circuits
➢
Analyse the phasor concept, instantaneous power, and average power.
➢
Define the active and reactive power
3. Three Phase AC Circuits
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➢
Describe three phase systems, their advantages, and their connection types.
➢
Analyse a three phase systems
Reza Razzaghi
Introduction to Power Systems
Objectives of Week1
1. Introduction to Power Systems
➢
➢
Describe power system structure, from generation to distribution.
Reflect on the new challenges in power networks and potential solutions
2. Single Phase AC Circuits
➢
Analyse the phasor concept, instantaneous power, and average power.
➢
Define the active and reactive power
3. Three Phase AC Circuits
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➢
Describe three phase systems, their advantages, and their connection types.
➢
Analyse a three phase systems
Reza Razzaghi
Introduction to Power Systems
Power Systems Structure
A brief historical background
❑ Edison designed the entire electrical system
in 1878 established the first power company.
❑ In the 1950s and 1960s, isolated systems were
converted to large regional pools:
▪ Bulk delivery over long distances
▪ Large generation plants.
❑ With economies of scale, prices declined
and demands increased.
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Introduction to Power Systems
Power Systems Structure
The traditional structure of an interconnected electrical power systems is characterized by the following
hierarchical layers:
➢ Generation systems (power plants);
➢ Transmission and sub-transmission networks (rated voltages of 500 kV, 330 kV, 275 kV, 220 kV and 132 kV);
➢ Distribution systems (rated voltages of 50 kV, 20 kV, 15 kV, 11 kV and, for the low voltage, 0.4 kV).
Source: qca
Generation
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Transmission
Distribution
Introduction to Power Systems
Power Systems Structure
Large power plants generate electric power using
synchronous generators. These machines are generally
characterised by rated voltages of 8,15 or 20 kV as a
function of their power. Their physical connection to the
transmission grid is realised by means of power transformers
that are increasing the voltage to the rated value of the
transmission network (i.e. 380 kV, …).
The network “A” is transmission network and allows the
transport the electrical energy for long distances. The main
characteristic of the network is that it is meshed with typical
distances between nodes in the range of 50 - 200 km. The
main aim of the this network is to transport the electricity
with high reliability levels and relatively low losses.
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Introduction to Power Systems
Power Systems Structure
Lines “E” are interconnecting, at state or country scale,
state/country transmission networks.
They allow the exchanges in normal and emergency
conditions (i.e., market trading by tie-lines or emergency
recovery after a blackout).
These lines allows to increase the reliability and the
economy of the operation of the entire electrical
infrastructure.
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Introduction to Power Systems
Power Systems Structure
• Nodes “S” are connected, by means of dedicated
stations, to networks “B” called sub-transmission
networks. These are characterised by typical rated
voltages of 66 kV.
• Typical distances between nodes of subtransmission networks are in the order of 30-40 km.
They are operated with a light-meshed structure.
• Sub-transmission networks supply both large
industrial customers or distribution networks by
dedicated stations called primary-substations
(nodes S’).
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Introduction to Power Systems
Power Systems Structure
• Power distribution networks “C”, have typical rated
voltages of 50 kV, 33 kV 22 kV, and 11 kV and a
structure that is purely radial.
• These networks provide energy to public services
and customers with maximum rated power
between (typically) 1 - 5 MW.
• The size of these networks does not exceeds 10-20
km for the case of overhead lines (rural networks)
and a few km for the case of cable lines (urban
networks).
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Introduction to Power Systems
Power Systems Structure
• Networks “D” compose the low-voltage distribution
with rated voltage (for instance in Europe) of 400 V
(230 V single phase). These networks supply loads
within 3 to 40 kW.
• The extension of these networks is of few hundreds of
meters in urban contexts or max 1 km in rural
contexts. The low-voltage distribution networks are
radial.
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Introduction to Power Systems
Power Systems Structure
1. Generation systems
Transform some type of energy to electric energy.
Coal fired generation
Open cycle gas fired generation
Combined cycle gas fired generation
Sources: AER, Babcock and Brown.
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Introduction to Power Systems
Power Systems Structure
1. Generation systems
Hydroelectric generation
Wind generation
Sources: AER, Babcock and Brown.
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Introduction to Power Systems
Solar generation
Wind Generation
1. Generation systems
Offshore wind turbines near Copenhagen
Source: Tony Moran/Shutterstock
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Hornsdale wind farm with the Tesla battery
Source: Utility magazine
Introduction to Power Systems
Solar Generation
1. Generation systems
Credit: GreenMPs
Credit: Lyon Group, Kingfisher project
Credit: Worklife Siemens/flickr
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Introduction to Power Systems
Power Generation by Source NEM- June 2017
Source: ARENA
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Introduction to Power Systems
Live Supply & Demand
https://reneweconomy.com.au/nem-watch/
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Introduction to Power Systems
Power Systems Structure
2. Transmission networks
• Transmission networks transfer bulk electricity from the
generation sites over long distances to substations closer
to areas of demand for electricity.
• In Transmission networks, the electricity is transmitted at
high voltages (110 kV or above) to reduce the energy loss
which occurs in long-distance transmission.
➢ Around 40,000 km high voltage transmission line in
Australia.
• Overhead lines or underground lines
▪ Underground lines costs are 10 to 20 times higher
▪ Maintenance in underground lines is much more
expensive.
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Source: PJM learning centre
Introduction to Power Systems
Power Systems Structure
Transmission networks main components
Transformers
Source: etap
Measurement transformers
Source: ABB
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Lines and towers
HV circuit breaker
Source: T&D world
Source: Hitachi
Protection relays
Communication
Source: SEL
Source: qualitypower
Introduction to Power Systems
Power Systems Structure
3. Sub-transmission networks
• A sub-transmission facility serves as an intermediate point between the transmission system
and the distribution system that supplies the electricity to customers.
• Lower voltage typically ranging between 66kV and 138kV
• Lower voltage sub-transmission lines are often desirable because the land areas through
which the transmission lines pass needed by higher voltage transmission lines may be
unavailable in more heavily-populated areas.
• Sub-transmission circuits are usually arranged in loops so that a single line failure does not cut
off service to a large number of customers for more than a short time.
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Introduction to Power Systems
Power Systems Structure
4. Distribution networks
• Distribution lines are the final stage in the delivery
of electricity to the end users.
• Electricity must be stepped down to lower
voltages in a distribution network for safe use by
customers.
• In general, there is one-directional electricity flow
from the substation to the consumers.
• It can be over or under ground distribution system.
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Source: PJM learning centre
Introduction to Power Systems
Power Systems Structure- National Electricity Market (NEM)
One of the world’s longest interconnected power systems, covering
a distance of around 5,000 kilometers.
The NEM incorporates around 40,000 km of transmission lines and
cables.
NEM is managed by Australian Energy Market Operator (AEMO).
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NEM regions
Qld, NSW, Vic, SA, Tas
Installed capacity
54,421 MW
Nr of registered generators
336
Nr of customers
9.6 million
Total energy generated
200 TWh
Strategic reserves of demand and
generation
1000 MW
Reza Razzaghi
Introduction to Power Systems
Power Systems Structure- National Electricity Market (NEM)
http://www.aemo.com.au/aemo/apps/visualisations/map.html
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Introduction to Power Systems
Future power networks and critical role of
power engineers
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Introduction to Power Systems
Future Electricity Generation Share- Worldwide
Electricity sources shift
World – thousand TWh (net delivered)
Source: exxonmobil
Global electricity demand grows by 60 percent from 2016 to
2040.
The world shifts to lower carbon sources for electricity generation,
led by natural gas, renewables such as wind and solar, and
nuclear.
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Globally, wind and solar’s share of delivered electricity
grows significantly from about 5 percent in 2016 to about
17 percent in 2040.
Introduction to Power Systems
Future Electricity Generation Share- Australia
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Projections of NEM generation capacity
NEM coal generation fleet operating life to 2050, by
50th year from full operation or announced retirement.
Source: AEMO, Integrated System Plan Consultation, 2017
Source: Australian Energy Council, 2016. Submission to the Parliamentary
enquiry, Retirement of coal fired power station
Reza Razzaghi
Introduction to Power Systems
Future Electricity Generation Share- NEM
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Introduction to Power Systems
https://opennem.org.au/#/all-regions/energy
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Introduction to Power Systems
Future Electricity Generation Share- NEM
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Introduction to Power Systems
Australian PV installations since 2007
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Introduction to Power Systems
Integration of DERs in Power Systems
Where renewables and CHP installations are typically located ?
Large-scale generation
Distributed generation
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Concentrated solar
Offshore
wind
Large hydro
District CHP
Large
onshore wind
Industrial CHP
Mini hydro
Small
onshore wind
Medium CHP
Photovoltaic
Micro CHP
Dispatchable sources
Continuous sources
Intermittent
Introduction to Power Systems
Distribution networks Transmission networks
Network connection
Distance to user
Integration of DERs in Power Systems - Challenges
Challenges - Passive → active DN
Transmission
Sub-transmission
Distribution (medium
voltage)
Distribution
Without
distributed
generation
Unidirectional
powerflows
from
transmission to
distribution
networks.
(low voltage)
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Reza Razzaghi
Introduction to Power Systems
Integration of DERs in Power Systems - Challenges
Challenges - Passive → active DN
Transmission
Sub-transmission
Distribution (medium
voltage)
Distribution
With
distributed
generation
Bidirectional
powerflows
between the
transmission to
distribution
infrastructures.
(low voltage)
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Introduction to Power Systems
Integration of DERs in Power Systems - Challenges
What would be the challenges of integrating
renewable energy resources in power networks?
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Reza Razzaghi
Introduction to Power Systems
Integration of DERs in Power Systems - Challenges
Challenges - Passive → active distribution networks
How much distributed generation can we connect to existing grids without any control action ?
% of network nodes
Statistical evaluation of the impact of embedded generation on distribution
networks operation constraints (steady state)
Lines power flow limits
Fast voltage variations
Slow voltage variations
No violated constraints
Connected generation [MW]
Adapted from [M. Delfanti, M. Merlo, G. Monfredini, V. Olivieri, M. Pozzi, A. Silvestri, A., “Hosting Dispersed Generation on Italian MV networks: Towards smart grids”,
14th International Conference on Harmonics and Quality of Power (ICHQP), 2010]
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Introduction to Power Systems
Integration of DERs in Power Systems - Challenges
Volatility of DERs
65%
Example of daily measured power injected by a PV system.
Solar
irradiance
2s
source: Prof. Mario Paolone, Distributed Electrical Systems Lab, EPFL
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Introduction to Power Systems
Integration of DERs in Power Systems - Challenges
Variability of DERs
Rooftop solar is not visible to AEMO in real time, and cannot currently be controlled or coordinated.
However, it can be seen on the grid as the well-known “duck curve” – namely, low demand in the
middle of the day, with a larger ramp to the evening peak.
average operational demand
Remark#1: possibility to have phases along the day
with large reduction of the net power flow on the
transmission network.
Remark#2: need of faster ramping in the evening
hours
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Introduction to Power Systems
Integration of DERs in Power Systems - Challenges
South Australia Blackout
Source: ABC
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Introduction to Power Systems
Take Home
❖ Power systems structure
❖ Overview of generation, transmission, and distribution systems
❖ Changes happening in power systems and the associated challenges
Next Lecture: Fundamentals of AC circuits
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Introduction to Power Systems