Power Generation Concepts: Detailed Notes | Power Systems - Electrical Engineering (EE) PDF Download

 Page 1


  
Introduction: 
Electric energy is produced in large quantities at various electric power plants by converting 
different forms of energy fossil fuels, nuclear energy, water power, etc. Electric energy is transformed by 
the use of transformers to different voltage levels most suitable for transmission, distribution and 
consumption. Electric power is transmitted using overhead or cable lines to customers at varied distances 
from its sources. Electric energy is utilized by various conversion devices such as electric motors, electric 
ovens, lighting systems, air condition units, etc. The need for power transmission lines arises from the fact 
that bulk electric power generation is done at electric power plants remote from consumers. However, 
consumers require small amounts of energy and they are scattered over wide areas. Thus the 
transmission of energy over a distance offers a number of advantages such as the following: 
1. Use of remote energy sources. 
2. Reduction of the total power reserve of generations 
3. Utilization of the time difference between various time zones when the peak demands are not 
coincidence. 
4. Improved reliability of electric power supply. 
The different power stations located in different geographical locations are interconnected by 
transmission lines thereby forming a power system network usually referred to as the GRID. This chapter 
presents an overview of the power system structure and principles of power generation. 
STRUCTURE OF POWER SYSTEMS: 
Generating stations, transmission lines and the distribution systems are the main components of 
an electric power system. Generating stations and a distribution station are connected through 
transmission lines, which also connect one power system (grid, area) to another. A distribution system 
connects all the loads in a particular area to the transmission lines. For economical and technological 
reasons, individual power systems are organized in the form of electrically connected areas or regional 
grids (also called power pools). Each area or regional grid operates technically and economically 
independently, but these are eventually interconnected* to form a national grid (which may even form an 
international grid) so that each area is contractually tied to other areas in respect to certain generation 
and scheduling features. Nigeria has a 330kV national grid. 
The major advantages of interconnecting power systems include the following: 
? Increased reliability: In the event of a forced or planned outage of a power station, the affected 
system can be fed from other stations. River flow, storage facilities, floods, and draughts are the 
factors that may affect hydrogenation, for example. Outages can easily be met by load transfer once 
systems are interconnected. 
Page 2


  
Introduction: 
Electric energy is produced in large quantities at various electric power plants by converting 
different forms of energy fossil fuels, nuclear energy, water power, etc. Electric energy is transformed by 
the use of transformers to different voltage levels most suitable for transmission, distribution and 
consumption. Electric power is transmitted using overhead or cable lines to customers at varied distances 
from its sources. Electric energy is utilized by various conversion devices such as electric motors, electric 
ovens, lighting systems, air condition units, etc. The need for power transmission lines arises from the fact 
that bulk electric power generation is done at electric power plants remote from consumers. However, 
consumers require small amounts of energy and they are scattered over wide areas. Thus the 
transmission of energy over a distance offers a number of advantages such as the following: 
1. Use of remote energy sources. 
2. Reduction of the total power reserve of generations 
3. Utilization of the time difference between various time zones when the peak demands are not 
coincidence. 
4. Improved reliability of electric power supply. 
The different power stations located in different geographical locations are interconnected by 
transmission lines thereby forming a power system network usually referred to as the GRID. This chapter 
presents an overview of the power system structure and principles of power generation. 
STRUCTURE OF POWER SYSTEMS: 
Generating stations, transmission lines and the distribution systems are the main components of 
an electric power system. Generating stations and a distribution station are connected through 
transmission lines, which also connect one power system (grid, area) to another. A distribution system 
connects all the loads in a particular area to the transmission lines. For economical and technological 
reasons, individual power systems are organized in the form of electrically connected areas or regional 
grids (also called power pools). Each area or regional grid operates technically and economically 
independently, but these are eventually interconnected* to form a national grid (which may even form an 
international grid) so that each area is contractually tied to other areas in respect to certain generation 
and scheduling features. Nigeria has a 330kV national grid. 
The major advantages of interconnecting power systems include the following: 
? Increased reliability: In the event of a forced or planned outage of a power station, the affected 
system can be fed from other stations. River flow, storage facilities, floods, and draughts are the 
factors that may affect hydrogenation, for example. Outages can easily be met by load transfer once 
systems are interconnected. 
? Reduction in total installed capacity: In an isolated system reserve units must be maintained 
separately in power station. However, the reduction in total installed capacity depends on the 
characteristics of the interconnected system and the desired degree of service reliability. 
? Economic operation. 
Components of electric power systems: 
There Are 4 Components of Electrical Power System 
1. Power system Generation  
2. Transmission  
3. Distribution  
4. Utilization 
Power system Generation: 
Electricity generation is the process of generating electric power from energy. The fundamental 
principles of electricity generation were discovered during the 1820s and early 1830s by the British 
scientist Michael Faraday. His basic method is still used today: electricity is generated by the movement of 
a loop of wire, or disc of copper between the poles of a magnet. For electric utilities, it is the first process 
in the delivery of electricity to consumers. The other processes, electricity transmission, distribution, and 
electrical power storage and recovery using pumped-storage methods are normally carried out by 
the electric power industry. Electricity is most often generated at a power station by electro mechanical 
generators, primarily driven by heat engines fueled by chemical combustion or nuclear but also by other 
means such as the kinetic energy of flowing water and wind. Other energy sources include solar photo 
voltaic and geothermal power. 
There are seven fundamental methods of directly transforming other forms of energy into electrical 
energy: 
? Static electricity, from the physical separation and transport of charge (examples: triboelectric 
effect and lightning) 
? Electromagnetic induction, where an electrical generator, dynamo or 
alternator transforms kinetic energy (energy of motion) into electricity. This is the most used 
form for generating electricity and is based on Faraday's law. It can be experimented by simply 
rotating a magnet within closed loops of a conducting material (e.g. copper wire) 
? Electrochemistry, the direct transformation of chemical energy into electricity, as in 
a battery, fuel cell or nerve impulse 
? Photoelectric effect, the transformation of light into electrical energy, as in solar cells 
? Thermoelectric effect, the direct conversion of temperature differences to electricity, as 
in thermocouples, thermopiles, and thermionic converters. 
Page 3


  
Introduction: 
Electric energy is produced in large quantities at various electric power plants by converting 
different forms of energy fossil fuels, nuclear energy, water power, etc. Electric energy is transformed by 
the use of transformers to different voltage levels most suitable for transmission, distribution and 
consumption. Electric power is transmitted using overhead or cable lines to customers at varied distances 
from its sources. Electric energy is utilized by various conversion devices such as electric motors, electric 
ovens, lighting systems, air condition units, etc. The need for power transmission lines arises from the fact 
that bulk electric power generation is done at electric power plants remote from consumers. However, 
consumers require small amounts of energy and they are scattered over wide areas. Thus the 
transmission of energy over a distance offers a number of advantages such as the following: 
1. Use of remote energy sources. 
2. Reduction of the total power reserve of generations 
3. Utilization of the time difference between various time zones when the peak demands are not 
coincidence. 
4. Improved reliability of electric power supply. 
The different power stations located in different geographical locations are interconnected by 
transmission lines thereby forming a power system network usually referred to as the GRID. This chapter 
presents an overview of the power system structure and principles of power generation. 
STRUCTURE OF POWER SYSTEMS: 
Generating stations, transmission lines and the distribution systems are the main components of 
an electric power system. Generating stations and a distribution station are connected through 
transmission lines, which also connect one power system (grid, area) to another. A distribution system 
connects all the loads in a particular area to the transmission lines. For economical and technological 
reasons, individual power systems are organized in the form of electrically connected areas or regional 
grids (also called power pools). Each area or regional grid operates technically and economically 
independently, but these are eventually interconnected* to form a national grid (which may even form an 
international grid) so that each area is contractually tied to other areas in respect to certain generation 
and scheduling features. Nigeria has a 330kV national grid. 
The major advantages of interconnecting power systems include the following: 
? Increased reliability: In the event of a forced or planned outage of a power station, the affected 
system can be fed from other stations. River flow, storage facilities, floods, and draughts are the 
factors that may affect hydrogenation, for example. Outages can easily be met by load transfer once 
systems are interconnected. 
? Reduction in total installed capacity: In an isolated system reserve units must be maintained 
separately in power station. However, the reduction in total installed capacity depends on the 
characteristics of the interconnected system and the desired degree of service reliability. 
? Economic operation. 
Components of electric power systems: 
There Are 4 Components of Electrical Power System 
1. Power system Generation  
2. Transmission  
3. Distribution  
4. Utilization 
Power system Generation: 
Electricity generation is the process of generating electric power from energy. The fundamental 
principles of electricity generation were discovered during the 1820s and early 1830s by the British 
scientist Michael Faraday. His basic method is still used today: electricity is generated by the movement of 
a loop of wire, or disc of copper between the poles of a magnet. For electric utilities, it is the first process 
in the delivery of electricity to consumers. The other processes, electricity transmission, distribution, and 
electrical power storage and recovery using pumped-storage methods are normally carried out by 
the electric power industry. Electricity is most often generated at a power station by electro mechanical 
generators, primarily driven by heat engines fueled by chemical combustion or nuclear but also by other 
means such as the kinetic energy of flowing water and wind. Other energy sources include solar photo 
voltaic and geothermal power. 
There are seven fundamental methods of directly transforming other forms of energy into electrical 
energy: 
? Static electricity, from the physical separation and transport of charge (examples: triboelectric 
effect and lightning) 
? Electromagnetic induction, where an electrical generator, dynamo or 
alternator transforms kinetic energy (energy of motion) into electricity. This is the most used 
form for generating electricity and is based on Faraday's law. It can be experimented by simply 
rotating a magnet within closed loops of a conducting material (e.g. copper wire) 
? Electrochemistry, the direct transformation of chemical energy into electricity, as in 
a battery, fuel cell or nerve impulse 
? Photoelectric effect, the transformation of light into electrical energy, as in solar cells 
? Thermoelectric effect, the direct conversion of temperature differences to electricity, as 
in thermocouples, thermopiles, and thermionic converters. 
? Piezoelectric effect, from the mechanical strain of electrically anisotropic molecules or crystals. 
Researchers at the US Department of Energy's Lawrence Berkeley National Laboratory (Berkeley 
Lab) have developed a piezoelectric generator sufficient to operate a liquid crystal display using 
thin films of M13 bacteriophage.  
? Nuclear transformation, the creation and acceleration of charged particles 
(examples: betavoltaics or alpha particle emission) 
? Static electricity was the first form discovered and investigated, and the electrostatic generator is 
still used even in modern devices such as the Van de Graaff generator and MHD generators. 
Charge carriers are separated and physically transported to a position of increased electric 
potential. 
? Almost all commercial electrical generation is done using electromagnetic induction, in 
which mechanical energy forces an electrical generator to rotate. There are many different 
methods of developing the mechanical energy, including heat engines, hydro, wind and tidal 
power. 
? The direct conversion of nuclear potential energy to electricity by beta decay is used only on a 
small scale. In a full-size nuclear power plant, the heat of a nuclear reaction is used to run a heat 
engine. This drives a generator, which converts mechanical energy into electricity by magnetic 
induction. 
? Most electric generation is driven by heat engines. The combustion of fossil fuels supplies most 
of the heat to these engines, with a significant fraction from nuclear fission and some 
from renewable sources. The modern steam turbine (invented by Parsons in 1884) currently 
generates about 80% of the electric power in the world using a variety of heat sources. 
 
Electric-power transmission: 
 
? Electric-power transmission is the bulk transfer of electrical energy, from generating power 
plants to electrical substations located near demand centers. This is distinct from the local wiring 
between high-voltage substations and customers, which is typically referred to as electric power 
distribution. 
? Transmission lines, when interconnected with each other, become transmission networks. In the 
US, these are typically referred to as "power grids" or just "the grid." In the UK, the network is 
known as the "National Grid". North America has three major grids, the Western 
Interconnection, the Eastern Interconnection and the Electric Reliability Council of Texas (ERCOT) 
grid, often referred to as the Western System, the Eastern System and the Texas System. 
Page 4


  
Introduction: 
Electric energy is produced in large quantities at various electric power plants by converting 
different forms of energy fossil fuels, nuclear energy, water power, etc. Electric energy is transformed by 
the use of transformers to different voltage levels most suitable for transmission, distribution and 
consumption. Electric power is transmitted using overhead or cable lines to customers at varied distances 
from its sources. Electric energy is utilized by various conversion devices such as electric motors, electric 
ovens, lighting systems, air condition units, etc. The need for power transmission lines arises from the fact 
that bulk electric power generation is done at electric power plants remote from consumers. However, 
consumers require small amounts of energy and they are scattered over wide areas. Thus the 
transmission of energy over a distance offers a number of advantages such as the following: 
1. Use of remote energy sources. 
2. Reduction of the total power reserve of generations 
3. Utilization of the time difference between various time zones when the peak demands are not 
coincidence. 
4. Improved reliability of electric power supply. 
The different power stations located in different geographical locations are interconnected by 
transmission lines thereby forming a power system network usually referred to as the GRID. This chapter 
presents an overview of the power system structure and principles of power generation. 
STRUCTURE OF POWER SYSTEMS: 
Generating stations, transmission lines and the distribution systems are the main components of 
an electric power system. Generating stations and a distribution station are connected through 
transmission lines, which also connect one power system (grid, area) to another. A distribution system 
connects all the loads in a particular area to the transmission lines. For economical and technological 
reasons, individual power systems are organized in the form of electrically connected areas or regional 
grids (also called power pools). Each area or regional grid operates technically and economically 
independently, but these are eventually interconnected* to form a national grid (which may even form an 
international grid) so that each area is contractually tied to other areas in respect to certain generation 
and scheduling features. Nigeria has a 330kV national grid. 
The major advantages of interconnecting power systems include the following: 
? Increased reliability: In the event of a forced or planned outage of a power station, the affected 
system can be fed from other stations. River flow, storage facilities, floods, and draughts are the 
factors that may affect hydrogenation, for example. Outages can easily be met by load transfer once 
systems are interconnected. 
? Reduction in total installed capacity: In an isolated system reserve units must be maintained 
separately in power station. However, the reduction in total installed capacity depends on the 
characteristics of the interconnected system and the desired degree of service reliability. 
? Economic operation. 
Components of electric power systems: 
There Are 4 Components of Electrical Power System 
1. Power system Generation  
2. Transmission  
3. Distribution  
4. Utilization 
Power system Generation: 
Electricity generation is the process of generating electric power from energy. The fundamental 
principles of electricity generation were discovered during the 1820s and early 1830s by the British 
scientist Michael Faraday. His basic method is still used today: electricity is generated by the movement of 
a loop of wire, or disc of copper between the poles of a magnet. For electric utilities, it is the first process 
in the delivery of electricity to consumers. The other processes, electricity transmission, distribution, and 
electrical power storage and recovery using pumped-storage methods are normally carried out by 
the electric power industry. Electricity is most often generated at a power station by electro mechanical 
generators, primarily driven by heat engines fueled by chemical combustion or nuclear but also by other 
means such as the kinetic energy of flowing water and wind. Other energy sources include solar photo 
voltaic and geothermal power. 
There are seven fundamental methods of directly transforming other forms of energy into electrical 
energy: 
? Static electricity, from the physical separation and transport of charge (examples: triboelectric 
effect and lightning) 
? Electromagnetic induction, where an electrical generator, dynamo or 
alternator transforms kinetic energy (energy of motion) into electricity. This is the most used 
form for generating electricity and is based on Faraday's law. It can be experimented by simply 
rotating a magnet within closed loops of a conducting material (e.g. copper wire) 
? Electrochemistry, the direct transformation of chemical energy into electricity, as in 
a battery, fuel cell or nerve impulse 
? Photoelectric effect, the transformation of light into electrical energy, as in solar cells 
? Thermoelectric effect, the direct conversion of temperature differences to electricity, as 
in thermocouples, thermopiles, and thermionic converters. 
? Piezoelectric effect, from the mechanical strain of electrically anisotropic molecules or crystals. 
Researchers at the US Department of Energy's Lawrence Berkeley National Laboratory (Berkeley 
Lab) have developed a piezoelectric generator sufficient to operate a liquid crystal display using 
thin films of M13 bacteriophage.  
? Nuclear transformation, the creation and acceleration of charged particles 
(examples: betavoltaics or alpha particle emission) 
? Static electricity was the first form discovered and investigated, and the electrostatic generator is 
still used even in modern devices such as the Van de Graaff generator and MHD generators. 
Charge carriers are separated and physically transported to a position of increased electric 
potential. 
? Almost all commercial electrical generation is done using electromagnetic induction, in 
which mechanical energy forces an electrical generator to rotate. There are many different 
methods of developing the mechanical energy, including heat engines, hydro, wind and tidal 
power. 
? The direct conversion of nuclear potential energy to electricity by beta decay is used only on a 
small scale. In a full-size nuclear power plant, the heat of a nuclear reaction is used to run a heat 
engine. This drives a generator, which converts mechanical energy into electricity by magnetic 
induction. 
? Most electric generation is driven by heat engines. The combustion of fossil fuels supplies most 
of the heat to these engines, with a significant fraction from nuclear fission and some 
from renewable sources. The modern steam turbine (invented by Parsons in 1884) currently 
generates about 80% of the electric power in the world using a variety of heat sources. 
 
Electric-power transmission: 
 
? Electric-power transmission is the bulk transfer of electrical energy, from generating power 
plants to electrical substations located near demand centers. This is distinct from the local wiring 
between high-voltage substations and customers, which is typically referred to as electric power 
distribution. 
? Transmission lines, when interconnected with each other, become transmission networks. In the 
US, these are typically referred to as "power grids" or just "the grid." In the UK, the network is 
known as the "National Grid". North America has three major grids, the Western 
Interconnection, the Eastern Interconnection and the Electric Reliability Council of Texas (ERCOT) 
grid, often referred to as the Western System, the Eastern System and the Texas System. 
? Historically, transmission and distribution lines were owned by the same company, but starting in 
the 1990s, many countries have liberalized the regulation of the electricity market in ways that 
have led to the separation of the electricity transmission business from the distribution business.  
? Most transmission lines use high-voltage three-phase alternating current (AC), although single 
phase AC is sometimes used in railway electrification systems. High-voltage direct-
current (HVDC) technology is used for greater efficiency in very long distances (typically hundreds 
of miles (kilo meters), or in submarine power cables (typically longer than 30 miles (50 km)). 
HVDC links are also used to stabilize against control problems in large power distribution 
networks where sudden new loads or blackouts in one part of a network can otherwise result in 
synchronization problems and cascading failures. 
? Electricity is transmitted at high voltages (110 kV or above) to reduce the energy lost in long-
distance transmission. Power is usually transmitted through overhead power lines. Underground 
power transmission has a significantly higher cost and greater operational limitations but is 
sometimes used in urban areas or sensitive locations. 
? A key limitation in the distribution of electric power is that, with minor exceptions, electrical 
energy cannot be stored, and therefore must be generated as needed. A sophisticated control 
system is required to ensure electric generation very closely matches the demand. If the demand 
for power exceeds the supply, generation plants and transmission equipment can shut down 
which, in the worst cases, can lead to a major regional blackout, such as occurred in the US 
Northeast blackouts of 1965, 1977,2003, and other regional blackouts in 1996 and 2011. To 
reduce the risk of such failures, electric transmission networks are interconnected into regional, 
national or continental wide networks thereby providing multiple redundant alternative routes 
for power to flow should (weather or equipment) failures occur. Much analysis is done by 
transmission companies to determine the maximum reliable capacity of each line (ordinarily less 
than its physical or thermal limit) to ensure spare capacity is available should there be any such 
failure in another part of the network. 
 
Electricity distribution systems: 
? Electricity distribution is the final stage in the delivery 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 (1kV to 72.5kV)
[1]
 power lines, substations 
and pole-mounted transformers, low-voltage (less than 1 kV) distribution wiring and some times 
meters. 
? The modern distribution system begins as the primary circuit leaves the sub-station and ends as 
the secondary service enters the customer's meter socket by way of a service drop. Distribution 
Page 5


  
Introduction: 
Electric energy is produced in large quantities at various electric power plants by converting 
different forms of energy fossil fuels, nuclear energy, water power, etc. Electric energy is transformed by 
the use of transformers to different voltage levels most suitable for transmission, distribution and 
consumption. Electric power is transmitted using overhead or cable lines to customers at varied distances 
from its sources. Electric energy is utilized by various conversion devices such as electric motors, electric 
ovens, lighting systems, air condition units, etc. The need for power transmission lines arises from the fact 
that bulk electric power generation is done at electric power plants remote from consumers. However, 
consumers require small amounts of energy and they are scattered over wide areas. Thus the 
transmission of energy over a distance offers a number of advantages such as the following: 
1. Use of remote energy sources. 
2. Reduction of the total power reserve of generations 
3. Utilization of the time difference between various time zones when the peak demands are not 
coincidence. 
4. Improved reliability of electric power supply. 
The different power stations located in different geographical locations are interconnected by 
transmission lines thereby forming a power system network usually referred to as the GRID. This chapter 
presents an overview of the power system structure and principles of power generation. 
STRUCTURE OF POWER SYSTEMS: 
Generating stations, transmission lines and the distribution systems are the main components of 
an electric power system. Generating stations and a distribution station are connected through 
transmission lines, which also connect one power system (grid, area) to another. A distribution system 
connects all the loads in a particular area to the transmission lines. For economical and technological 
reasons, individual power systems are organized in the form of electrically connected areas or regional 
grids (also called power pools). Each area or regional grid operates technically and economically 
independently, but these are eventually interconnected* to form a national grid (which may even form an 
international grid) so that each area is contractually tied to other areas in respect to certain generation 
and scheduling features. Nigeria has a 330kV national grid. 
The major advantages of interconnecting power systems include the following: 
? Increased reliability: In the event of a forced or planned outage of a power station, the affected 
system can be fed from other stations. River flow, storage facilities, floods, and draughts are the 
factors that may affect hydrogenation, for example. Outages can easily be met by load transfer once 
systems are interconnected. 
? Reduction in total installed capacity: In an isolated system reserve units must be maintained 
separately in power station. However, the reduction in total installed capacity depends on the 
characteristics of the interconnected system and the desired degree of service reliability. 
? Economic operation. 
Components of electric power systems: 
There Are 4 Components of Electrical Power System 
1. Power system Generation  
2. Transmission  
3. Distribution  
4. Utilization 
Power system Generation: 
Electricity generation is the process of generating electric power from energy. The fundamental 
principles of electricity generation were discovered during the 1820s and early 1830s by the British 
scientist Michael Faraday. His basic method is still used today: electricity is generated by the movement of 
a loop of wire, or disc of copper between the poles of a magnet. For electric utilities, it is the first process 
in the delivery of electricity to consumers. The other processes, electricity transmission, distribution, and 
electrical power storage and recovery using pumped-storage methods are normally carried out by 
the electric power industry. Electricity is most often generated at a power station by electro mechanical 
generators, primarily driven by heat engines fueled by chemical combustion or nuclear but also by other 
means such as the kinetic energy of flowing water and wind. Other energy sources include solar photo 
voltaic and geothermal power. 
There are seven fundamental methods of directly transforming other forms of energy into electrical 
energy: 
? Static electricity, from the physical separation and transport of charge (examples: triboelectric 
effect and lightning) 
? Electromagnetic induction, where an electrical generator, dynamo or 
alternator transforms kinetic energy (energy of motion) into electricity. This is the most used 
form for generating electricity and is based on Faraday's law. It can be experimented by simply 
rotating a magnet within closed loops of a conducting material (e.g. copper wire) 
? Electrochemistry, the direct transformation of chemical energy into electricity, as in 
a battery, fuel cell or nerve impulse 
? Photoelectric effect, the transformation of light into electrical energy, as in solar cells 
? Thermoelectric effect, the direct conversion of temperature differences to electricity, as 
in thermocouples, thermopiles, and thermionic converters. 
? Piezoelectric effect, from the mechanical strain of electrically anisotropic molecules or crystals. 
Researchers at the US Department of Energy's Lawrence Berkeley National Laboratory (Berkeley 
Lab) have developed a piezoelectric generator sufficient to operate a liquid crystal display using 
thin films of M13 bacteriophage.  
? Nuclear transformation, the creation and acceleration of charged particles 
(examples: betavoltaics or alpha particle emission) 
? Static electricity was the first form discovered and investigated, and the electrostatic generator is 
still used even in modern devices such as the Van de Graaff generator and MHD generators. 
Charge carriers are separated and physically transported to a position of increased electric 
potential. 
? Almost all commercial electrical generation is done using electromagnetic induction, in 
which mechanical energy forces an electrical generator to rotate. There are many different 
methods of developing the mechanical energy, including heat engines, hydro, wind and tidal 
power. 
? The direct conversion of nuclear potential energy to electricity by beta decay is used only on a 
small scale. In a full-size nuclear power plant, the heat of a nuclear reaction is used to run a heat 
engine. This drives a generator, which converts mechanical energy into electricity by magnetic 
induction. 
? Most electric generation is driven by heat engines. The combustion of fossil fuels supplies most 
of the heat to these engines, with a significant fraction from nuclear fission and some 
from renewable sources. The modern steam turbine (invented by Parsons in 1884) currently 
generates about 80% of the electric power in the world using a variety of heat sources. 
 
Electric-power transmission: 
 
? Electric-power transmission is the bulk transfer of electrical energy, from generating power 
plants to electrical substations located near demand centers. This is distinct from the local wiring 
between high-voltage substations and customers, which is typically referred to as electric power 
distribution. 
? Transmission lines, when interconnected with each other, become transmission networks. In the 
US, these are typically referred to as "power grids" or just "the grid." In the UK, the network is 
known as the "National Grid". North America has three major grids, the Western 
Interconnection, the Eastern Interconnection and the Electric Reliability Council of Texas (ERCOT) 
grid, often referred to as the Western System, the Eastern System and the Texas System. 
? Historically, transmission and distribution lines were owned by the same company, but starting in 
the 1990s, many countries have liberalized the regulation of the electricity market in ways that 
have led to the separation of the electricity transmission business from the distribution business.  
? Most transmission lines use high-voltage three-phase alternating current (AC), although single 
phase AC is sometimes used in railway electrification systems. High-voltage direct-
current (HVDC) technology is used for greater efficiency in very long distances (typically hundreds 
of miles (kilo meters), or in submarine power cables (typically longer than 30 miles (50 km)). 
HVDC links are also used to stabilize against control problems in large power distribution 
networks where sudden new loads or blackouts in one part of a network can otherwise result in 
synchronization problems and cascading failures. 
? Electricity is transmitted at high voltages (110 kV or above) to reduce the energy lost in long-
distance transmission. Power is usually transmitted through overhead power lines. Underground 
power transmission has a significantly higher cost and greater operational limitations but is 
sometimes used in urban areas or sensitive locations. 
? A key limitation in the distribution of electric power is that, with minor exceptions, electrical 
energy cannot be stored, and therefore must be generated as needed. A sophisticated control 
system is required to ensure electric generation very closely matches the demand. If the demand 
for power exceeds the supply, generation plants and transmission equipment can shut down 
which, in the worst cases, can lead to a major regional blackout, such as occurred in the US 
Northeast blackouts of 1965, 1977,2003, and other regional blackouts in 1996 and 2011. To 
reduce the risk of such failures, electric transmission networks are interconnected into regional, 
national or continental wide networks thereby providing multiple redundant alternative routes 
for power to flow should (weather or equipment) failures occur. Much analysis is done by 
transmission companies to determine the maximum reliable capacity of each line (ordinarily less 
than its physical or thermal limit) to ensure spare capacity is available should there be any such 
failure in another part of the network. 
 
Electricity distribution systems: 
? Electricity distribution is the final stage in the delivery 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 (1kV to 72.5kV)
[1]
 power lines, substations 
and pole-mounted transformers, low-voltage (less than 1 kV) distribution wiring and some times 
meters. 
? The modern distribution system begins as the primary circuit leaves the sub-station and ends as 
the secondary service enters the customer's meter socket by way of a service drop. Distribution 
circuits serve many customers. The voltage used is appropriate for the shorter distance and 
varies from 2,300 to about 35,000 volts depending on utility standard practice, distance, and load 
to be served. Distribution circuits are fed from a transformer located in an electrical substation, 
where the voltage is reduced from the high values used for power transmission. 
? Conductors for distribution may be carried on overhead pole lines, or in densely-populated areas 
where they are buried underground. Urban and suburban distribution is done with three-
phase systems to serve residential, commercial, and industrial loads. Distribution in rural areas 
may be only single-phase if it is not economical to install three-phase power for relatively few 
and small customers. 
? Only large consumers are fed directly from distribution voltages; most utility customers are 
connected to a transformer, which reduces the distribution voltage to the relatively low voltage 
used by lighting and interior wiring systems. The transformer may be pole-mounted or set on the 
ground in a protective enclosure. In rural areas a pole-mount transformer may serve only one 
customer, but in more built-up areas multiple customers may be connected. In very dense city 
areas, a secondary network may be formed with many transformers feeding into a common bus 
at the utilization voltage. Each customer has a service drop connection and a meter for billing. 
(Some very small loads, such as yard lights, may be too small to meter and so are charged only a 
monthly rate.) 
? A ground connection to local earth is normally provided for the customer's system as well as for 
the equipment owned by the utility. The purpose of connecting the customer's system to ground 
is to limit the voltage that may develop if high voltage conductors fall on the lower-voltage 
conductors, or if a failure occurs within a distribution transformer. If all conductive objects are 
bonded to the same earth grounding system, the risk of electric shock is minimized. However, 
multiple connections between the utility ground and customer ground can lead to stray 
voltage problems; customer piping, swimming pools or other equipment may develop 
objectionable voltages. These problems may be difficult to resolve since they often originate 
from places other than the customer's premises. 
 
Electric utility: 
? An electric utility is an electric power company (often a public utility) that engages in 
the generation, transmission, and distribution of electricity for sale generally in a regulated 
market. The electrical utility industry is a major provider of energy in most countries. It is 
indispensable to factories, commercial establishments, homes, and even most recreational 
facilities. Lack of electricity causes not only inconvenience, but also economic loss due to reduced 
industrial production.