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Introduction to Electricity PART 1

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Title: Introduction to Electricity PART 1


1
Introduction to Electricity PART 1
2
Part 1 Introduction to Electricity
  • Basic Electricity
  • How Central Power Grids Work
  • Electricity Generation
  • STOP FOR TRANSLATION
  • ASK QUESTIONS ANY TIME

3
Part 1 Electricity Concepts
  • What is Electricity?
  • Electrons, atoms, negative charge
  • Conductors (example?)
  • Insulators (example?)
  • Electrical energy
  • Magnet

4
How does a generator work?
  • A generator is simply a device that moves a
    magnet to create a steady flow of electrons.
  • What moves the magnet? Water, or high pressure
    steam or gas drive turbine blades.

5
Process of Generation
6
Electrical Units
  • Three basic units of measurement
  • Voltage (volts)
  • Current (amps)
  • Resistance (ohms)

7
Water Analogy
  • Voltage water pressure
  • Current flow rate
  • Resistance pipe size

8
Key Concept
  • Lets say you have a tank of pressurized water
    connected to a hose that you use to water your
    vegetable garden. If you increase the pressure in
    the tank, more water comes out of the hose. Same
    for electrical systems increase the voltage you
    get a higher current of electrons.
  • OR if you increase the size of the hose more
    water can flow out. This is like reducing
    resistance in an electrical system, so you get
    more current.

9
Basic Electrical Circuit
  • All circuits have basic components a source of
    electricity (such as a battery), a load (a light
    or motor) and two wires to carry electricity
    between the two. Electrons move from the source,
    through the load, and back to the source.
  • These moving electrons have what we call energy.
    As they move they can do work.

10
Key Concept
  • In an electrical system, increasing either the
    current (i) or the voltage (V) will increase
    power output (P).
  • Increase resistance in the wires, voltage drops,
    current drops gt power output drops.

11
Electrical Circuits
  • Battery is a simple electrical circuit and source
  • When you load a battery into an electronic
    device, the negatively charged electrons will
    travel to the portion of the battery with a
    positive charge - much like water flowing down a
    stream and being forced to turn a water wheel.

12
How to calculate electricity consumption
  • In a lightbulb, electrical energy creates heat in
    the bulb, and the heat then creates light.
  • How much power in kilowatt-hours does a 100-watt
    lightbulb use in a year?
  • 0.1 kW x 8,760 hours in a year (24 x 365) or 876
    kilowatt-hours (kWh)

13
Household Electricity Consumption
  • In Thailand, the power outlets in the wall
    deliver 220 volts each. The frequency or the
    current is 50 cycles per second.
  • If you know the amps and volts, you can determine
    the amount of electricity consumed, which is
    measured in watts.
  • Most appliances are rated in watts. Say your
    appliance consumes 1,200 watts or 1.2 kilowatts.
    If you leave the appliance on for one hour the
    amount of electrical energy consumed is 1.2
    kilowatts per hour.

14
Your Electricity Bill
  • Power is measured in watts (voltage x current)
  • Consumption is measured in kilowatt-hours
  • How much does the power company charge you for
    electricity?

15
Electrical Current
  • Direct Current (DC)
  • Batteries (and solar cells) produce DC. The
    positive and negative terminals of a battery are
    always positive and negative. Current always
    flows in the same direction between the two
    terminals.

16
Electrical Current
  • Alternating Current (AC)
  • Power from a power plant is AC. The direction of
    the current reverses or alternates.
  • In Thailand, AC moves at 50 cycles per second.
  • Power from a wall socket is 220 volts, 50-cycle
    single-phase AC power.

17
Key Concept
  • There is an advantage in using less current to
    make the same amount of power. The resistance in
    electrical wires consumes power as current
    increases, more power consumed.
  • Using a higher voltage to reduce the current
    makes electrical system more efficient.

18
Part 2 How Central Power Systems Work
19
The Power Plant
  • This is where electrical power begins. In most
    cases, the plant consists of a spinning
    electrical generator. Something some kind of
    force or pressure - has to make the generator
    spin. It might be a turbine in a hydroelectric
    dam, a large diesel engine, or a gas turbine.
    Often a steam turbine is used to spin the
    generator. The steam is created by burning coal,
    oil or natural gas. Or the steam may be generated
    in a nuclear station.

20
Power Plants Generate 3-phase AC Power
  • Commercial generators of any size generate what
    is called 3-phase AC power.
  • There are 4 wires coming out of every power plant
    the three phases plus a ground.

21
Transmission Substation
  • 3-phase power leaves the generator and enters a
    transmission substation at the power plant. This
    substation uses large transformers to convert the
    generators voltage (thousands of volts) up to
    extremely high voltages for long distance
    transmission on the grid.

22
Transmission Lines
  • Typical voltages for long distance transmission
    range from 155 to 765 kilovolts (1 kilo is 1000)
  • A typical long distance transmission is under 500
    kilometres.

23
Power Substation
  • The power substation does 2 or 3 things
  • transformers bring down the voltage to
    distribution voltages.
  • a busbar splits the distribution power off in
    multiple directions.
  • circuit breakers and switches to allow the
    substation to be disconnected from the
    transmission grid or separate distribution lines.

24
Electricity Distribution
  • To use power in homes and temples, power from the
    transmission grid must be stepped down to the
    distribution grid.
  • Conversion from transmission voltage to standard
    line voltage 7.2 kV (kilovolts)

25
Distribution Line to End Users
  • The transformer drum steps down electricity from
    7.2 kilovolts to 240 volts for normal household
    electrical service.
  • The 240 volts enters your house through a typical
    watt-hour meter.
  • The meter allows the power company to charge you
    (the end user) the cost of putting up all these
    wires and consuming electricity delivered to your
    house, office, factory, etc.

26
Key Concept
  • AC power has one big advantage voltage can be
    changed (up or down) using a device called a
    transformer. Power companies save money using
    very high voltages to transmit power over long
    distances.

27
Part 3 Electricity Generation
  • Generation Technologies
  • Steam turbines
  • Gas turbines
  • Wind turbines
  • Hydro/hydraulic turbines
  • Combined cycle plants
  • Cogeneration
  • Microturbines
  • Solar photovoltaics (DC power)

28
Dams Use Hydraulic (Water) Turbines
29
Coal Plants Use Steam Turbines
30
Nuclear Reactors use steam turbines
31
Biomass Generation
32
Biomass Gasifier Power Plant
33
Combined Cycle Power Plants use gas steam
turbines
34
Combined Cycle Plants use gas turbine and steam
turbine
35
Solar Photovoltaics
36
Solar On-Grid/Off-Grid Technology
37
Characteristics of Generating Plants
  • Size, generating capacity
  • Energy/fuel source
  • Efficiency conversion to electrical energy
  • Type of use
  • Availability

38
Generation Capacity
  • Depends on size of the hydraulic turbine, the
    electric generator and the height of the water
    (head).
  • The volume of water behind the dam affects the
    maximum amount of energy that may be generated in
    a given period of time.

39
Power Plant Size (Capacity)
  • Range from a few kilowatts to gt1,000 MW
  • Microturbines are the smallest (see Capstone
    video for a tour of a microturbine cogeneration
    facility)

40
Generation Efficiency
  • The efficiency of a generating unit is a measure
    of the amount of electrical energy produced per
    unit of energy input.
  • For thermal plants (plants burning fuel), the
    energy input is fuel and the way efficiency is
    measured is called the heat rate.
  • The more fuel that has to be burned to produce
    electricity, the lower the thermal efficiency.

41
Comparing Plant Efficiency
  • Newer combined cycle plants have near 50 percent
    thermal efficiency compared to coal or nuclear
    plants which can only convert 30 percent of their
    fuel into electrical energy (the rest is released
    into the atmosphere as waste heat).

42
Type of Use Base, Intermediate, Peak Load
  • In a central power system, power plants are
    designed and operated for base load,
    intermediate load, and peak load.
  • Base load usually large units with low
    operating costs. Usually operated at full
    capacity during most of the hours they are
    available. Designed to operate for long periods
    of time at or near maximum dependable capacity.
    Low operating costs refer to low cost of the fuel
    they use.

43
Intermediate Load
  • Power plants used to respond to variations in
    customer demand which occur during the day.
    Plants designed for change in output levels.

44
Type of Use Peak Load
  • Peak load power plant is called upon to supply
    customer demand during peak ( highest) load
    hours of a given day, month, season or year.
  • Combustion turbines and small hydro units
    usually less than 150 MW, capable of achieving
    full load operation within 10 minutes. They may
    also be used to replace capacity of other units
    that have suddenly been taken off the system due
    to forced outages.

45
Plant Availability Dispatch
  • System operators are concerned about availability
    of each power plant to supply the grid.
  • System operators dispatch power plants according
    to their availability (and operating cost).
  • On a day to day and hour to hour basis there must
    sufficient generation synchronized to the grid to
    meet all load requirements and respond to
    short-term variations in customer load, as well
    as cover for the loss of another generator.

46
Availability vs Outages
  • Unavailability of a generating unit due to
    component failure is called a forced outage.
  • Various components of generating units must be
    removed from service on a regular basis for
    preventive maintenance or to replace components
    before a forced outage results this is called a
    planned outage.

47
Power System Reliability
  • 80 to 90 percent of power disruption in power
    systems today are caused by transmission grid,
    not generation.
  • Voltage dips in major transmission line gt other
    transmission lines within the system pick up
    additional load and may require central utility
    to redispatch generation gtinstability,
    overloading, blackouts.

48
Reserve Capacity
  • Central power systems designed to meet demand
    plus a reserve capacity, over and above the
    expected peak load obligation of the power plant
    (15 to 45 ).
  • Today big questions within the industry should
    the amount of installed generating capacity
    should be a design requirement (set by
    government) or should be determined by the
    market who should pay for transmission? MORE
    TOMORROW.

49
END Introduction to Electricity NEXT The
Electricity Industry
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