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

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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

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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

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Sources are:

Steam - Water is boiled by: nuclear fission, the burning of fossil fuels (coal, natural gas, or petroleum).

Introduction

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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

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Other renewable sources:

•Water (hydroelectric) - Turbine blades are acted upon by flowing water, produced by hydroelectric dams or tidal forces.

Introduction

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•Wind - Most wind turbines generate electricity from

naturally occurring wind.

Introduction

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Combine Cycle - gas turbine plants are

driven by both steam and natural gas.

Introduction

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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

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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

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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

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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

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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

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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