Power System Planning-Intro
-
Upload
mar-loun-amor-canales -
Category
Documents
-
view
43 -
download
1
Transcript of Power System Planning-Intro
POWER SYSTEM PLANNING
INTRODUCTION
Introduction Facts About the Power Industry
The electric power industry has evolved over many decades, from a low power generator, serving a limited area, to highly interconnected networks, serving a large number of countries, or even continents.
Nowadays, an electric power system is one of the man-made largest scale systems; ever made, comprising of huge number of components; starting from low power electric appliances to very high power giant turbo-generators.
Running this very large system is a real difficult task. It has caused numerous problems to be solved by both the educational and the industrial bodies.
The current situation should be run in an efficient manner, proper insights should be given to the future.
Introduction
Planning - to arrange a method or scheme beforehand
for any work, enterprise, or proceeding.
Power System Planning - discusses problem in terms of:
the issues involved from various viewpoints;
the methods to be used;
the elements to be affected;
the time horizon to be observed, etc
Introduction Power System Elements
As already noted, a typical power system is comprised of enormous number of elements. The elements may vary from a small lamp switch to a giant generator. However, the main elements of interest in this book are:
• Generation facilities
• Transmission facilities
– Substations
– Network (lines, cables)
• Loads
In power system planning, the details of each element design are not of main interest. For instance, for a generation facility, the type (steam turbine, gas turbine, etc.), the capacity and its location are only determined.
Introduction
Generation: source of power, ideally with a specified voltage and frequency
Load: consumes power; ideally with a constant resistive value
Transmission System: transmits power; ideally as a perfect conductor
Introduction
Introduction
5/12/2011 8
Electric Power Generation
• Electricity generation is the process of creating electricity from other forms of energy.
• For electric utilities, it is the first process in the delivery of electricity to consumers.
• Electricity is most often generated at a power station by electromechanical generators, primarily driven by heat engines fueled by chemical combustion or nuclear fission
• Other means such as the kinetic energy of flowing water and wind.
• There are many other technologies that can be and are used to generate electricity such as solar photovoltaics and geothermal power.
Introduction
5/12/2011 9
Methods of generating electricity
Turbines
All turbines are driven by a fluid acting as an intermediate energy carrier. Other types of turbines can be driven by wind, steam or falling water.
Introduction
5/12/2011 10
Sources are:
Steam - Water is boiled by: nuclear fission, the burning of fossil fuels (coal, natural gas, or petroleum).
Introduction
5/12/2011 11
Renewables - the steam generated by:
•The sun as the heat source: solar parabolic troughs and solar power towers concentrate sunlight to heat a heat transfer fluid, which is then used to produce steam.
•Geothermal power. Either steam under pressure emerges from the ground and drives a turbine or hot water evaporates a low boiling liquid to create vapour to drive a turbine.
Introduction
5/12/2011 12
Other renewable sources:
•Water (hydroelectric) - Turbine blades are acted upon by flowing water, produced by hydroelectric dams or tidal forces.
Introduction
5/12/2011 13
•Wind - Most wind turbines generate electricity from
naturally occurring wind.
Introduction
5/12/2011 14
Combine Cycle - gas turbine plants are
driven by both steam and natural gas.
Introduction
5/12/2011 15
Electric Power Transmission
• Electric power transmission is the bulk transfer of electrical power (or energy), a process in the delivery of electricity to consumers.
• A power transmission network typically connects power plants to multiple substations near a populated area.
Introduction
5/12/2011 16
Generation, Transmission, Distribution and Utilization
1. Power plant 2. Step-Up Generating Transformer 3. Transmission 4. Step-Down Distribution Transformer 5. Distribution 6. Utilization
Introduction
5/12/2011 17
Usually transmission lines use three phase alternating current (AC). High-voltage direct current systems are used for long distance transmission, or some undersea cables.
Electricity is transmitted at high voltages (115 kV or above) to reduce the energy lost in transmission.
Power is usually transmitted as alternating current through overhead power lines.
Underground power transmission is used only in densely populated areas because of its higher cost of installation and maintenance when compared with overhead wires,and the difficulty of voltage control on long cables.
Introduction
5/12/2011 18
A power transmission network is referred to as a "grid". Multiple redundant lines between points on the network are provided so that power can be routed from any power plant to any load center, through a variety of routes, based on the economics of the transmission path and the cost of power.
In our country, The Philippine Grid Code (PGC)
establishes the basic rules, requirements, procedures,
and standards that govern the operation, maintenance,
and development of the high-voltage backbone
Transmission System in the Philippines.
Introduction
5/12/2011 19
Electric Power Distribution • Electricity distribution is the end stage in the
delivery (before retail) of electricity to end users.
• A distribution system's network carries electricity from the transmission system and delivers it to consumers.
• Typically, the network would include medium-voltage (less than 50 kV) power lines, electrical substations and pole-mounted transformers, low-voltage (less than 1000 V) distribution wiring and sometimes electricity meters.
Introduction
5/12/2011 20
General Layout of Electricity Networks
Introduction
Introduction
Complications No ideal voltage sources exist
Loads are seldom constant
Transmission system has resistance, inductance, capacitance and flow limitations
Simple system has no redundancy so power system will not work if any component fails
Introduction
Notation - Power
Power: Instantaneous consumption of energy
Power Units
Watts = voltage x current for dc (W)
kW – 1 x 103 Watt
MW – 1 x 106 Watt
GW – 1 x 109 Watt
Introduction
Notation - Energy Energy: Integration of power over time;
energy is what people really want from a power system
Energy Units
Joule = 1 Watt-second (J)
kWh – Kilowatthour (3.6 x 106 J)
Btu – 1055 J; 1 MBtu=0.292 MWh
Introduction
Source: DOE
Introduction
Source: DOE
Introduction
Source: DOE
Introduction
Source: DOE
Introduction
Source: DOE
Introduction
Power System Examples Electric utility: can range from quite small, such
as an island, to one covering half the continent – there are five major interconnected ac power systems
in the Philippines, each operating at 60 Hz ac; 50 Hz is used in some other countries.
Airplanes and Spaceships: reduction in weight is primary consideration; frequency is 400 Hz.
Ships and submarines
Automobiles: dc with 12 volts standard
Battery operated portable systems
Introduction
Source: DOE
Introduction
Electric Systems in Energy Context Class focuses on electric power systems, but
we first need to put the electric system in context of the total energy delivery system
Electricity is used primarily as a means for energy transportation – Use other sources of energy to create it, and it is
usually converted into another form of energy when used
About 40% of US energy is transported in electric form
Introduction
Energy Economics Electric generating technologies involve a
tradeoff between fixed costs (costs to build them) and operating costs – Nuclear and solar high fixed costs, but low operating
costs
– Natural gas/oil have low fixed costs but high operating costs (dependent upon fuel prices)
– Coal, wind, hydro are in between
Also the units capacity factor is important to determining ultimate cost of electricity
Introduction
Ball park Energy Costs Nuclear: $15/MWh
Coal: $22/MWh
Wind: $50/MWh
Hydro: varies but usually water constrained
Solar: $200/MWh
Natural Gas: 8 to 10 times fuel cost in $/MBtu
Note, to get price in cents/kWh take price in $/MWh and divide by 10.
Introduction
Natural Gas Prices – to 2007 Introduction
Oil Prices – to 2011
Introduction
Goals of Power System Operation Supply load (users) with electricity at
– specified voltage (120 ac volts common for residential)
– specified frequency
– with minimum cost (usually)
Introduction
Major Impediments Load is constantly changing
Power system is subject to disturbances, such as lightning strikes
Engineering tradeoffs between reliability and cost
Introduction
Example Yearly Electric Load
0
5000
10000
15000
20000
250001
518
1035
1552
2069
2586
3103
3620
4137
4654
5171
5688
6205
6722
7239
7756
8273
Hour of Year
MW
Lo
ad
Introduction
Power System Structure
Power System Structure
• The generations and the loads are distributed throughout the system.
• Due to both the technical and the economical viewpoints, the generation voltages may be as high as 33 kV or so, while the load voltages may be much lower.
• Moreover, the generation resources may be far away from load centers.
• To reduce the losses and to make the transmission possible, we have to convert the generation voltages to much higher values and to reconvert them to lower ones at the receiving ends (load centers).
• As a result, the interfaces between the generations and the loads may comprise of several voltages, such as 20, 63, 132, 230, 400, 500 kV or even higher.
Power System Structure
The available voltages depend much on each utility experiences within each country. However, regardless of what the available voltages are, it is of normal industrial practice to classify these voltages to:
• Transmission (for example, 230 kV and higher)
• Sub-transmission (for example, 63, 132 kV, and similar)
• Distribution4 (for example, 20 kV and 400 V).
Due to these various voltages, transformers are allocated throughout the network in the so called substations.
•For instance, a 400 kV substation5 may comprise of four 400 kV:230 kV transformers. Each substation is also equipped with circuit breakers, current and potential transformers, protection equipment, etc.
Power System Structure
Power System Studies, a Time-horizon Perspective Power System Structure
REFERENCES
[1] Power System Engineering - Planning, Design, and Operation of Power
Systems and Equipment, Juergen Schlabbach, Karl-Heinz Rofalski, 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim