Introduction to Electricity PART 1

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Introduction to Electricity PART 1
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Part 1 Introduction to Electricity

• Basic Electricity
• How Central Power Grids Work
• Electricity Generation
• STOP FOR TRANSLATION
• ASK QUESTIONS ANY TIME

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Part 1 Electricity Concepts

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

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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.

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Process of Generation
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Electrical Units

• Three basic units of measurement
• Voltage (volts)
• Current (amps)
• Resistance (ohms)

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Water Analogy

• Voltage water pressure
• Current flow rate
• Resistance pipe size

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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.

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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.

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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.

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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.

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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)

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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.

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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?

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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.

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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.

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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.

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Part 2 How Central Power Systems Work
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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.

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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.

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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.

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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.

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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.

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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)

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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.

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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.

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Part 3 Electricity Generation

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

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Dams Use Hydraulic (Water) Turbines
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Coal Plants Use Steam Turbines
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Nuclear Reactors use steam turbines
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Biomass Generation
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Biomass Gasifier Power Plant
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Combined Cycle Power Plants use gas steam
turbines
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Combined Cycle Plants use gas turbine and steam
turbine
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Solar Photovoltaics
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Solar On-Grid/Off-Grid Technology
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Characteristics of Generating Plants

• Size, generating capacity
• Energy/fuel source
• Efficiency conversion to electrical energy
• Type of use
• Availability

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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.

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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)

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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.

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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).

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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.

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Intermediate Load

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

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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.

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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.

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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.

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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.

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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.

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END Introduction to Electricity NEXT The
Electricity Industry