Title: Introduction to Electricity PART 1
1Introduction to Electricity PART 1
2Part 1 Introduction to Electricity
- Basic Electricity
- How Central Power Grids Work
- Electricity Generation
- STOP FOR TRANSLATION
- ASK QUESTIONS ANY TIME
-
3Part 1 Electricity Concepts
- What is Electricity?
- Electrons, atoms, negative charge
- Conductors (example?)
- Insulators (example?)
- Electrical energy
- Magnet
4How 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.
5Process of Generation
6Electrical Units
- Three basic units of measurement
-
- Voltage (volts)
- Current (amps)
- Resistance (ohms)
7Water Analogy
- Voltage water pressure
- Current flow rate
- Resistance pipe size
-
8Key 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.
9Basic 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.
10Key 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.
11Electrical 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.
12How 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)
13Household 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.
14Your 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?
15Electrical 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.
16Electrical 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.
17Key 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.
18Part 2 How Central Power Systems Work
19The 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.
20Power 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.
21Transmission 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.
22Transmission 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.
23Power 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.
24Electricity 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)
25Distribution 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.
26Key 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.
27Part 3 Electricity Generation
- Generation Technologies
- Steam turbines
- Gas turbines
- Wind turbines
- Hydro/hydraulic turbines
- Combined cycle plants
- Cogeneration
- Microturbines
- Solar photovoltaics (DC power)
28Dams Use Hydraulic (Water) Turbines
29Coal Plants Use Steam Turbines
30Nuclear Reactors use steam turbines
31Biomass Generation
32Biomass Gasifier Power Plant
33Combined Cycle Power Plants use gas steam
turbines
34Combined Cycle Plants use gas turbine and steam
turbine
35Solar Photovoltaics
36Solar On-Grid/Off-Grid Technology
37Characteristics of Generating Plants
- Size, generating capacity
- Energy/fuel source
- Efficiency conversion to electrical energy
- Type of use
- Availability
38Generation 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.
39Power 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)
40Generation 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).
42Type 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.
43Intermediate Load
- Power plants used to respond to variations in
customer demand which occur during the day.
Plants designed for change in output levels.
44Type 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.
45Plant 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.
46Availability 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.
47Power 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.
48Reserve 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.
49END Introduction to Electricity NEXT The
Electricity Industry