This chapter deals with the generation of different power system parts which includes the generation, transmission and distribution systems. This slide is specifically prepared for ASTU 5th year power and control engineering students.

1. POWER SYSTEM
PLANING AND
OPERATION
(PCE5312)
CHAPTER TWO: PLANNING
AND DESIGN
BY: MESFIN M.

2. Outline
Part One
➢General Overview of Generation Planning
➢Unit Size and Potentials of Energy Resources
➢Methods of Energy Conversion Technologies
➢Environmental and Social Impacts of Generation
Stations
3/13/2020

3. General Overview of Generation
Planning
– The previous section presented some overall
principles and complexities of system planning and
load forecasting.
– This section examines the major issues in the
development of a long-term expansion plan for the
generating systems and T&D System.
– The forecast of electrical demand is clearly one of
the most important components of a generating
system analysis.
3/13/2020

4. Cont.….
– The forecast typically must be for:
– Power (kW),
– Energy (kW-h) and
– Load variation for time intervals within a year,
– There are two distinct types of uncertainty in demand
forecasting.
– The uncertainty that results from the randomness of
the load at any time. E.g. Weather condition
– The other type of uncertainty is associated with the
estimate of future demand, May be too high or too low.
3/13/2020

5. Cont.…
– Underestimating future demand can create serious
difficulties,
– The result may be a generating system with low
reliability and the inability to serve some portion
of demand.
– Overestimating the demand is also undesirable,
– Because excess generating equipment imposes
increased costs on the system. 3/13/2020

6. Cont.…
– Generally, the function of an electric power system
is to provide a reliable and continuous source of
electricity whenever requested.
– To provide this service, each of the three main
components of an electric power system i.e.
generation, transmission and distribution must
perform as required.
3/13/2020

7. Con....
– The generation system consists of physical facilities that
convert energy resources (e.g. coal, oil, uranium,
running bodies of water) into electricity.
– The transmission system then transports the generated
electricity to the local service communities.
– The distribution system within each community
provides the actual connection from the transmission
system to each customer, and enables the customer to
consume electricity upon demand. 3/13/2020

8. Cont.…
– An electric power system is a dynamic system which is a
balance of supply and demand:
a) The supply of electricity, consisting of physical devices that
must be designed, constructed, operated, maintained, and
eventually replaced as each device wears out, and
b) The demand for electricity, which changes as a function of
time from instantaneous (seconds, minutes), to short term
(hours, days) and to the longer term (months, years).
3/13/2020

9. Cont.…
– The major objective for an electric power system is to
keep a continual balance between the supply and
demand for electricity.
– Power system expansion planning is the process of
analysing, evaluating and recommending what new
facilities and equipment must be added to the power
system in order to replace worn-out facilities and
equipment and to meet changing demand for electricity.
3/13/2020

10. Cont.…
– The aim of generation planning is to seek the most
economical generation expansion scheme achieving
a certain reliability level according of the forecast of
demand increase in a certain period of time.
– The following questions are to be answered
a) When to invest in new generating units?
b) Where to invest in new generating unit?
c) What type of generating unit to install?
d) What capacity of generating unit to install? 3/13/2020

11. Cont.…
– During generation planning the following issues shall be
addressed:
– The Generation type, location, technology, size, potential,
construction period and timing of future generation
plants that will be added to the power system.
– The generation investment cost, Operating and
Maintenance (O&M) cost both fixed and variable
costs
3/13/2020

12. Cont.…
– Generation fuel consumption or running cost for thermal
plants
– Environmental and social impacts and their associative costs
– Retirement plan for existing generation stations
– The annual average and firm energy of the generation
plants for the expected life time of each generation
plants.
– Long-run marginal generation cost for each kWh energy
unit.
3/13/2020

13. Unit size and Potentials of Energy
Resources
– The key parameters relevant to generating units
include unit sizes and the set of factors that
determine unit availabilities.
– The unit availability can be described in terms of
three contributing elements:
– Forced outage rates,
– Repair times and
– Scheduled maintenance.
3/13/2020

14. Cont.…
➢It is important in reliability analysis to recognize that unit
sizes directly influence forced outage rates on overall system
reliability.
– For example, a single unit rated at 1000 MW with a forced
outage rate of 10% does not result in the same performance
as 10 units rated at 100 MW each, all with forced outage
rates of 10%.
3/13/2020

15. Energy Resource Options
– They can be defined as net providers of energy
– Primary Energy Resources are subdivided into
– Non-renewable energy sources: fossil fuels (coal, oil,
natural gas (CH4)). Nonrenewable energy is energy
obtained from static stores of energy that remain bound
unless released by human interaction. Nonrenewable
energy supplies are also called finite supplies.
3/13/2020

16. Cont.…
– Renewable energy sources: solar energy, wind energy,
Hydropower, biomass sources; geothermal energy are
seasonally and slowly recovered energy sources.
– Renewable energy is the term used to cover those
energies that occur naturally and repeatedly in the
environment and can be harnessed for human benefit.
– The ultimate sources of most of these energies are the sun,
gravity and the earth’s rotation
3/13/2020

17. 1. Fossil fuel energy Recourses (Non-
Renewable Energy Resources)
– Energy technologies using oil, gas and coal are the basis of
most commercial energy supply systems.
– The systems that extract, process, transport and deliver fossil
fuels are characterized by large centralized facilities (e.g.
refineries, pipelines, coal mines).
– Obviously, the use of fossil fuels involves many different
stages and each stage has a variety of alternative
approaches.
3/13/2020

18. 2. Renewable Energy Resource
– Renewable resources are an important part of the energy
supply available to a country and must therefore be
considered as part of the resource base.
– However, these resources cannot be characterized in the
same way as fossil fuels.
– The definitions of the different types of 'reserves' do not
make sense for renewable.
– In some cases, for example solar and wind, the concept of
a reserve base has no real meaning.
3/13/2020

19. Cont.…
– Each renewable resource must be treated
somewhat differently and characterized separately
for planning purposes.
– Note that in almost all cases it is necessary to make
some assumptions about the performance of the
technology used to extract usable energy in order
to arrive at an estimate of the resource base.
– This is quite different from the process used for
fossil fuels.
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20. Cont.…
– Another factor complicating the analysis of
renewable resources is that many systems are not
large centralized facilities that can be analysed by
traditional project analysis techniques.
– Rather, there are many small decentralized systems
(solar water heaters, small wind electric generators,
biogas plants, mini-hydro plants, etc.) which must
be analysed in a different manner.
3/13/2020

21. Cont.…
– The user chooses the renewable system or the
conventional system on the basis of his perception
of.
– The delivered cost of energy (including investment
cost, fuel cost, operating costs, reliability,
convenience, etc.).
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22. Cont.…
– The different methods of renewable generation systems with the
corresponding types of fuel energy resources are indicated here.
3/13/2020

23. Methods of Energy
Conversion Technologies
➢Various technologies are currently available as
candidates for expanding electrical generating
systems.
➢Each has a unique set of characteristics that must
be considered from a system viewpoint to
determine the mix of future additions that provides
the best outcome for the stated objectives for
expansion. 3/13/2020

24. Cont.…
– In addition to existing technologies, long-term studies of
generation expansion must consider whether advanced
technologies will become available and, if so, what their
costs and characteristics will be.
– Power generation technologies may be classified into
existing major options and potential future options 3/13/2020

25. Cont.…
– Electrical power can be generated from several sources
of energy as given below:
a) By Conversion of Chemical Energy: in Coal, oil, Peat,
gas or other conventional fuels into heat by burning
and then into mechanical energy by hot gas or steam
rising and using it in a Gast or steam turbine
respectively. The Gas turbine or steam turbine drives a
generator which in turn produce electrical energy.
3/13/2020

26. Cont.…
b) By Conversion of Potential Energy in water stored in
elevated reservoirs to kinetic energy and then to
mechanical and electrical energy using hydraulic
turbines and generators.
c) By Conversion of Kinetic Energy in wind using wind
turbines and Generators
d) By Conversion of Nuclear Energy via heat and steam
into electrical power 3/13/2020

27. Cont.…
e) By Conversion of Geothermal energy in the Earth
using steam turbines to derive generators which in
turn generate Electrical power.
f) By Conversion of Solar Energy directly in to electrical
energy using solar cells and/or heat by solar radiation
and then into mechanical energy by steam turbines
which derives a generator to produce electrical power.
3/13/2020

28. Cont.…
– Existing Energy Conversion Methods and Process 3/13/2020

29. TYPES OF POWER GENERATING
PLANTS
– The existing types of power plants may be divided
mainly into the following groups.
✓Base,
✓Intermediate and
✓Peak loads
– These are classified according to the plant capacity
factor that defines rate at which the plant operates
throughout a year. 3/13/2020

30. Cont.…
– Plant Capacity Factor: is the ratio of the actual energy
produced to the maximum possible energy.
𝑷𝒍𝒂𝒏𝒕 𝑪𝒂𝒑𝒂𝒄𝒊𝒕𝒚 𝑭𝒂𝒄𝒕𝒐𝒓
= (𝑨𝒗𝒆𝒓𝒂𝒈𝒆 𝑳𝒐𝒂𝒅 + 𝑳𝒐𝒔𝒔𝒆𝒔)/𝑷𝒍𝒂𝒏𝒕 𝒊𝒏𝒔𝒕𝒂𝒍𝒍𝒆𝒅 𝒄𝒂𝒑𝒂𝒄𝒊𝒕𝒚
= [(𝑷𝒆𝒂𝒌 𝒍𝒐𝒂𝒅 ∗ 𝑳𝒐𝒂𝒅 𝑭𝒂𝒄𝒕𝒐𝒓)
+ (𝑳𝒐𝒔𝒔𝒆𝒔)]/𝑷𝒍𝒂𝒏𝒕 𝑪𝒂𝒑𝒂𝒄𝒊𝒕𝒚
= 𝒌𝑾𝒉 𝒈𝒆𝒏𝒆𝒓𝒂𝒕𝒆𝒅 𝒊𝒏 𝒂 𝒚𝒆𝒂𝒓/(𝒌𝑾𝒊𝒏𝒔𝒕 ∗ 𝟐𝟒 ∗ 𝟑𝟔𝟓)
3/13/2020

31. Cont.…
– For base load operation the chief requirements are:
✓low specific operating cost (i.e. cost/kWh supplied)
✓high availability
✓High capital cost, since it can be spread over a large
amount of energy, is normally acceptable
✓The ability to provide a rapidly changing output is not
important
3/13/2020

32. Cont.…
– For a peak load operations the desired requirements are:
✓Ability to start and provide full output within, say, 30 minutes.
✓Low capital cost (because this can only be spread over a small
amount of energy), with operating cost being only secondary
considerations.
✓A siting near generation centres or accessible transmission
facilities so as to minimize transmission costs and losses.
✓It is advantageous if the peak load plant can in emergency be
used as a back up to supply the base load.
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33. – For maximum reliability and economy it would be desirable to have a close match between
system generation capacity and system demand.
– The power system planner should take these factors into account when considering system
requirements.
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34. Environmental and Social
Impacts of Generation Station
– During the conceptual and design phases of a new power
plant, or during expansion of an existing facility,
environmental factors should be considered;
1. Emissions into the atmosphere
– Sulphur dioxide is produced by combustion of the sulphur
contained in coal.
– Particulates come from ash in the fuel being burned. They have
been linked to a variety of lung diseases, soiling of buildings and
clothing, and crop damage.
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35. Cont.…
2. Thermal pollution
– No process is completely efficient, and thermal emissions occur in
thermal power plants (fossil or nuclear).
– The difference between the theoretical and actual amounts is the
thermal emission from the power plant.
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36. Outline
Part Two
– Classification and Characteristics of Transmission Lines
– Critical Considerations for Transmission system Planning
– Transmission Design and Modelling
– Distribution system planning
3/13/2020

37. T&D Planning and Design
– Transmission and distribution (T&D)
system consists of thousands of
transmission and distribution lines,
substations, transformers, and other
equipment scattered over a wide
geographical area and interconnected
so that all function concerted to
deliver power as needed to the
utility's customers.
3/13/2020

38. Cont.…
– The transmission planning determines the expansion or
rehabilitation plan of transmission system based on the
existing system, forecasted demand, generation schedule
and generation location at a least cost, stable, reliable and
efficient planning criteria.
– Some of the issues to be consider in the transmission
network planning are:
3/13/2020

39. Cont.…
– The need for new substations and transmission lines as
well as the need for reinforcement in the existing
system
– The voltage levels and right-of-way constraints
– The investment cost, O&M cost
– Line loadability, reliability, stability analysis
– substation Capacity, reliability and switching stability
3/13/2020

40. Cont.…
– Compensating equipment requirements for voltage
stability
– System network stability (Voltage magnitude,
generator angle or voltage angle and Frequency) and
reliability during contingency and fault cases
– Modelling each component of a power system and
analysis the steady state and transient stabilities as well
as the fault levels at each node of the network. 3/13/2020

41. Cont.…
– Power transmission from generating stations to
industrial sites and to substations is the fundamental
objective of the transmission systems.
– This function is accomplished by
– Overhead AC or DC transmission lines
– Underground cables
3/13/2020

42. Cont.…
– The conception of a transmission line and substations
starts in.
– Long-term planning: with initial system evaluations
– Medium-term planning:
– Finally with the detail design and installation of the
line and then the granting of operation licence and
approval.
3/13/2020

43. Cont.…
– For completing the preliminary studies of a new line, some
complementary studies of performance assessment are carried
out such as:
3/13/2020
– Rout length alternatives,
– Line load ability,
– Voltage level and number
of circuits,
– Reactive compensation
needs,
– load-flows and stability,
– Transposition needs,
– Switching surge over
voltages,
– Short-circuit levels,
– Reliability evaluation and
Contingency evaluations.

44. Cont.…
– Finally, the line owner proceeds to the line basic design
and then detailed design with all associated activities.
– The last stages consist in establishing the rights-of-way,
performing and approving environmental impact
studies and providing compensation to the land owners
affected by the new line in order to obtain their
agreement.
– The commissioning of the line and start-up of
operation ends the process.
3/13/2020

45. Classification and Characteristics of
Transmission Lines
– Electrical power system consist:
– Generation system,
– Transmission system -132-765 kV
– Sub-transmission system - 34.5 – 115 kV
– Distribution system - below 34.5 kV
– Since the long distance transmission at high voltage is cheap
and, low voltages are required for utility purposes, the
voltage level goes on decreasing from bulk transmission
system to the distribution system.
3/13/2020

46. Cont.…
– An electric transmission line has four parameters, namely
resistance, inductance, capacitance and shunt conductance.
– These parameters are uniformly distributed along the whole
line.
– The line parameters are functions of the line-geometry,
construction material and operational frequency.
– The line resistance and inductance form the series
impedance of the line. While the capacitance and
conductance form the shunt admittance of the line.
3/13/2020

47. Cont.…
– These parameters together with the load current and
power factor determine the electrical performance of
the line.
– The term performance includes the calculation-end
voltage, sending-end current, sending-end power
factor, Power loss in the line, efficiency of
transmission, regulation and limits of power flow
during steady-state and transient conditions.
3/13/2020

48. Cont.…
➢Transmission lines are classified in to:
– Short- up to 80 km: For over head line the capacitance C
and shunt conductance G are negligibly small but for
cable lines the effect of capacitance can not ignored
– medium - from 80 to 240 km: For these lines, the
capacitance of the line cannot be neglected but
conductance is neglected.
– long- more than 240 km: The long line treatment takes
all the four parameters in to account
3/13/2020

49. Cont.…
– According to their voltage class, there are five types
power transmission lines:
– Low-voltage (LV) lines - less than 1000 volts, provide
power to buildings, factories, and houses to drive
motors, electric stoves, lamps, heaters, and air
conditioners. The lines are insulated conductors,
usually made of aluminium
3/13/2020

50. Cont.…
– Medium-Voltage (MV)- between 2.4 kV and 69 kV,
Such medium voltage radial distribution systems are
preferred in larger cities.
– High-Voltage (HV) lines- from 69 kV to 230 kV,
connect the main substations to the generation
stations; connect two isolated sub-transmission
systems or two separate generation stations
3/13/2020

51. Cont.…
– Extra high Voltage (EHV) - from 230kV to 760 kV,
are used when generating stations are very far from
the load centres.
– Ultra-high-Voltage (UHV) - above 760 kV, transfer
bulk electrical energy from remote large scale power
stations to the extra-high or high voltage
substations.
3/13/2020

52. Voltage selection for transmission of
electrical energy
3/13/2020

53. Cont.…
– The system voltage very much affects the capital cost
of a transmission line,
– The weight of conductor material, the efficiency of
the line, the voltage drop in the line and the system
stability depend upon the system voltage thus, choice
of voltage becomes major factor in the line design.
3/13/2020

54. Cont.…
𝑃 = 𝑉𝐼 cos 𝜙 ; 𝐼 =
𝑃
𝑉 cos 𝜙
; 𝐴 =
𝐼
𝛼
=
𝑃
𝛼𝑉 cos 𝜙
𝑤ℎ𝑒𝑟𝑒 𝛼 𝑖𝑠 𝑐𝑢𝑟𝑟𝑒𝑛𝑡 𝑑𝑒𝑛𝑠𝑖𝑡𝑦 𝐴/𝑚2
– The resistance of each conductors is given by
𝑅 = 𝜌
𝐿
𝐴
=
𝜌𝐿𝛼𝑉 cos 𝜙
𝑃
– Power loss: the power loss in the line per phase
𝑃𝐿 = 𝐼2
𝑅 =
𝑃
𝑉 cos 𝜙
2
.
1
𝑃
(𝜌𝐿𝛼𝑉 cos 𝜙) =
𝛼𝜌𝐿𝑃
𝑉 cos 𝜙
𝑊
3/13/2020

55. Cont.…
– Voltage drop in the resistance : the voltage in the resistance
per phase is = 𝐼𝑅 = 𝐴𝛼𝜌
𝐿
𝐴
= 𝛼𝜌𝐿
– The percentage voltage drop in resistance in a line is =
𝐼𝑅
𝑉
×
100% =
𝛼𝜌𝐿
𝑉
× 100%
– The voltage drop in the resistance per phase is, therefore,
constant for a given value of current density and percentage
voltage drop in resistance decreases with increase in the
system voltage.
3/13/2020

56. Cont.…
– Weight of Conductor Material : Let 𝛿 is the density of the
material ;the weight of the conductor material required for
each phase is:
𝑤 = 𝐴𝐿𝛿 =
𝑃𝐿𝛿
𝛼𝑉 cos 𝜙
– Transmission efficiency:
𝜂 𝑇 =
𝐿𝑖𝑛𝑒 𝑜𝑢𝑡𝑝𝑢𝑡
𝐿𝑖𝑛𝑒 𝑜𝑢𝑡𝑝𝑢𝑡 + 𝐿𝑖𝑛𝑒 𝑙𝑜𝑠𝑠
=
𝑃
𝑃 +
𝛼𝜌𝐿𝑃
𝑉 cos 𝜙
= (1 +
𝛼𝜌𝐿
𝑉 cos 𝜙
)−1 = 1 −
𝛼𝜌𝐿
𝑉 cos 𝜙
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57. Assignment I (5 pts)
1. Explain EHVAC and HVDC Transmission Systems
2. Explain HVDC Transmission- Advantages and
Disadvantages
3. List common tower configurations of HVAC and
HVDC transmission systems.
Due date: 12/03/2020
3/13/2020

58. Assignment II (5 pts)
1. Explain reactive power compensation and its
importance in power system.
2. Explain the two basic types of system compensation
3. List different compensation devices found in a
substation.
Due date: 12/03/2020
3/13/2020

59. Critical Considerations for
Transmission system Planning
– In general, planning a new transmission addition
includes several important aspects of the overall
power system, namely:
3/13/2020
❖Real and Reactive Power
Flow Analysis
❖Economics of the new
transmission line
❖Stability issues due to
the new line
❖Interchange capability
❖Reliability issues
❖Environmental impact

60. Cont.…
3/13/2020
The logic diagram for transmission expansion study.

61. Transmission Line Design
✓It would be necessary to transmit a certain amount of power, at given power
factor, a given distance and be with the limit of the given voltage regulation and
efficiency
✓ The line should withstand the weather conditions (wind pressure, temperature
variation, ice etc) of locality in which they are laid
❑The electrical design involves selection of:-
- transmission voltage
- conductors (type, size, and number of bundle per-phase)
- the number and type of insulator disc per phase
- spacing of conductors (phase-to-phase clearance, phase-to ground clearance
(tower))
- the number, type and location of shield wires 3/13/2020

62. ❑Selection of transmission (distribution) voltage:- The line voltage is
determined by the load and distance over which it is to be transmitted.
❑The most economical voltage is given by the empirical formula
for three-phase system.
Where
V = Line voltage in kV
L = Line length (distance), km
P = Load in MW
3/13/2020
V = 5.5 ×
L
1.6
+ 10P
Cont.…

63. ✓Then the selected voltage should be the largest nearest standard
voltage.
❑Selection of conductor size:- The size of conductor is selected in
view of the following factors:
- current carrying capacity
- allowable voltage drop (or voltage regulation)
- corona discharge
- mechanical strength (break down strength) 3/13/2020
Cont.…

64. ❑ Spacing of conductors:-
➢ The spacing of conductors is determined by voltage of the lines and spans length used.
➢ The practically recommended spacing of conductor in general will be given in mechanical
design consideration latter.
➢ For approximate calculation either of the following formulas may be used for aluminum
conductor
Where, D is in m, V is line-to-line voltage in kV, and S0 is sag in m.
Or
Where D = spacing in mm
V = line to line voltage in kV
L = span length in m
3/13/2020
D = S0 +
V
150
D = 500 + 18V +
L2
50
Cont.…

65. ❑Insulator selection: -
➢ The insulator type and number of insulator discs
➢Up to line voltage of 35kV pin-type insulators are normally used.
➢Above this voltage suspension type insulators are used.
➢ One disc in suspension insulator can with stand approximately rated
voltage of 13-15kV.
3/13/2020
Cont.…

66. ❑Mechanical design consideration of over head T & D lines
• Transmission lines should be designed with necessary mechanical strength
to counter the stress due to weather conditions in the area in which the
transmission lines are located.
• The conductors supported on poles (tower) should be designed in such a
way that the tension does not exceed the permissible limit.
• The characteristics of conductors, sag-tension relation, permissible clearance
from the ground and effect of variation of temperature and consequent
changes in the stress should be considered in stringing procedures f
insulator discs in transmission line 3/13/2020
Cont.…

67. ✓The span, sag and tension have the following relations:
3/13/2020
S0 =
W.g.L2
8.T
,m
Where W = weight of conductor per unit length (kg/m)
L = span length (m)
g = gravitational constant (1kgf = 9.81N)
T = tension on conductor (N)
sag-tension relation,
Cont.…

68. ✓The span, sag and tension have the following relations:
3/13/2020
• The overall height of pole or tower is calculated
Ho = C + S0 + 3SA + SB + SC + SE
Where: C = stationary clearance to ground
SA = length of insulator suspension set
SB, SC, SE = vertical distance between cross arm and
conductor, cross- arm and earth wire
S0 = sag of conductor proportional to square of span (L)
Cont.… Permissible clearance from the ground

69. ✓The minimum clearance for different voltage level
3/13/2020
Cont.…

70. Distribution system planning
– Distribution planners must determine the peak load
magnitude and its geographic location
– Then distribution substations must be placed and
sized in such a way as to serve a certain load at
minimum cost by minimizing feeder losses and
construction costs, while considering the constraints
of service reliability, such as the voltage of substations
and feeders, and capacity constraints.
3/13/2020

71. Cont.…
– Physically, the primary distribution system can be
divided into two distinct subsystems:
– The substations and
– The primary feeder circuit.
3/13/2020

72. Cont.…
– In each subsystem a number of variables must be
considered in the planning stage, as follows:
1. Substations: location, number, transformer rating
and loading, and service areas;
2. Primary feeder circuit: number of primary feeders,
feeder routing, feeder branch loading, and conductor
size.
3/13/2020

73. End of Chapter Two
Next
Chapter Three
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