electric power systems (module 1)
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BEE 3243ELECTRIC POWER SYSTEMS
(Module 1)
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BEE 3243 Electric Power Systems – Module 1
Objectives
(1) To understand the electric power systems
(2) To have knowledge on the main components of an electric power systems
(3) To learn the basic knowledge of power flow
(4) To conduct fault analysis in power systems
(5) To get approach on power systems protection schemes
Lecture Plan
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BEE 3243 Electric Power Systems – Module 1
Learning Outcomes
At the end of this course, student should have the ability to:
(1) describe the structure and the main energy sources for an electric power systems
(2) explain the basic components which are consist in an electric power systems
(3) determine various types of generating system such as thermal, hydro, nuclear, and renewable energy station
Cont…
Lecture Plan
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BEE 3243 Electric Power Systems – Module 1
Learning Outcomes
(4) analyse the short, medium, and long transmission lines
(5) perform and study of simple power flow program
(6) describe the important elements in a distributionsystem and its protection schemes
(7) analyse the possible fault in an electric power systems
(8) design various protection schemes for electric power systems
Lecture Plan
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BEE 3243 Electric Power Systems – Module 1
Syllabus
• Module 1 – Introduction to Power System (1-2)• Module 2 – Components of an Electric Power System (3-4)• Module 3 – Generation System (5)• Module 4 – Transmission System (6-7)• Module 5 – Distribution System (7-8)• Module 6 – Introduction to Power Flow Studies (9-10)• Module 7 – Fault in Electric Power System (11-12)• Module 8 – Power System Protection (13-14)
Lecture Plan
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BEE 3243 Electric Power Systems – Module 1
Teaching & Assessment Approaches
Teaching Approaches• Lecture (14 weeks)• Tutorial (Each module)• Project & Assignment
– Prototype of Electrical Power System (Due: Week 5)– Matlab Simulation on Power Flow/ Fault Analysis
Assessment Approaches1. Quiz : 05%2. Assignment : 05%3 Test : 30%4. Project : 15%5. Others : 05%6. Final Examination : 40%
Total : 100%
Lecture Plan
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BEE 3243 Electric Power Systems – Module 1
References1. Electrical Machines, Drives and Power Systems; Theodore Wildi, Prentice
Hall, 2006.2. Electric Machinery and Power System Fundamentals; Chapman Stephen J.,
McGraw-Hill, 2002.3. Power System Analysis (2nd Edition); Hadi Saadat, Prentice Hall, 2004.4. Electric Power Systems (4th Edition); Weedy B. M. and Cory B. J., John
Wiley & Sons, 1998.
Other References :1. Electrical Power and Controls (2nd Edition); Timothy L. S, William E. D.,
Prentice Hall, 2004.2. Power System Analysis and Design (3rd Edition); J. Duncan Glover and
Mulukutla S. Sarma,a. Brooks/ Cole Thomson Learning, 2002.3. Introduction to Power System Technology; Theodore R. Bosela, Prentice
Hall, 1997.
Lecture Plan
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Introduction to Power System
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BEE 3243 Electric Power Systems – Module 1
Introduction to Power System
1.1 Introduction1.2 History of Electric Power System1.3 The Sources of Electric Energy1.4 Modern Electric Power System1.5 National Grid, Malaysia1.6 Representation of Electric Power System1.7 Basic Computer Analysis of Electric Power System
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BEE 3243 Electric Power Systems – Module 1
Introduction
What is Electric Power System?Electric power system is a composite system of generation, transmission, and distribution systems.
Generation Stations
Transmission Lines
Distribution Systems
Step-up Transformers
Step-down Transformers Consumers
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BEE 3243 Electric Power Systems – Module 1
Introduction
The electricity produced by a generator travels along cables to a transformer, which changes electricity from low voltage to high voltage. Electricity can be moved long distances more efficiently using high voltage.
Transmission lines are used to carry the electricity to a substation.
Substations have transformers that change the high voltage electricity into lower voltage electricity.
From the substation, distribution lines carry the electricity to homes, offices and factories, which require low voltage electricity.
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BEE 3243 Electric Power Systems – Module 1
Introduction
How is Electricity Measured?
Electricity is measured in units of power called WATTS. 1 W = 1 J/s
1 hp = 745.7 W – use in machine rating.
A kilowatt represents 1,000 watts.
A kilowatt-hour (kWh) is equal to the energy of 1,000 watts working for one hour.For example, if you use a 100 W light bulb 8 hours a day, you have used 800 W of power, or 0.8 kWh of electrical energy.
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BEE 3243 Electric Power Systems – Module 1
History of Electric Power Systems
Thomas A. Edison opens Pearl St. Station, NYCWaterwheel-driven dc generator
installed in Appleton, Wisconsin
Frank J. Sprague produces dc motor for Edison systems
Nikola Tesla presents paper on two-phase ac induction and synchronous motors
First three-phase ac transmission line in Germany (12 kV, 179 km)
First transmission lines installed in Germany (2400 V dc, 59 km)
William Stanley develops commercially practical transformer
First single-phase ac transmission line in US, in Oregon (4 kV, 21 km)
First three-phase ac transmission line in US, in California (2.3 kV, 12 km)
1882
1884
1885/6
1888
1889
1891
1893
1882
1882
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BEE 3243 Electric Power Systems – Module 1
• Electricity – flow of electrical power or charge from one
point to another– The secondary energy sources that generated
from the conversion of other sources of energy, such as hydro, boimass,etc
Sources of Electric Energy
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BEE 3243 Electric Power Systems – Module 1
Sources of Electric Energy
Conventional/ Primary SourcesFossil Fuels
Coal
Oil (Diesel/ Petroleum)
Natural Gas
Nuclear power
Hydropower
Renewable/ Secondary SourcesGeothermal power
Solar power
Wind powerTidal power
Biomass
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BEE 3243 Electric Power Systems – Module 1
Coal – fossil fuel extracted from the ground
Sources of Electric Energy
-Has been used since the Industrial Revolution
-Easy to use because they require simple direct combustion
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BEE 3243 Electric Power Systems – Module 1
Natural Gas – gaseous fossil fuel consisting primarily of methane
Sources of Electric Energy
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BEE 3243 Electric Power Systems – Module 1
Nuclear power – is a method in which steam is produced by heating water through a process called nuclear fission
Sources of Electric Energy
- Other methods for nuclear reaction: nuclear fusion and radioactive decay
- All utility-scale reactors heat water to produce steam, which is then converted into mechanical work for the purpose of generating electricity or propulsion.
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BEE 3243 Electric Power Systems – Module 1
Hydropower – is a process in which flowing water is used to spin a turbine connected to a generator
Sources of Electric Energy
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BEE 3243 Electric Power Systems – Module 1
Geothermal power – is electricity generated by utilizing naturally occurring geological heat sources
Sources of Electric Energy
-Geothermal resources:
-shallow ground
-hot water and rock
-magma
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BEE 3243 Electric Power Systems – Module 1
Solar power – describes a number of methods of harnessing energy from the light of the Sun
Sources of Electric Energy
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BEE 3243 Electric Power Systems – Module 1
Wind power – is derived from the conversion of the energy contained in wind into electricity
Sources of Electric Energy
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BEE 3243 Electric Power Systems – Module 1
Biomass – (wood, agricultural waste, such as rice husk and bagasse, are some other energy sources for producing electricity.
Sources of Electric Energy
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BEE 3243 Electric Power Systems – Module 1
Sources of Electric Energy
Energy Generation According to Fuel Mix in Malaysia - 2003
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BEE 3243 Electric Power Systems – Module 1
• Future Trends of Energy Sources
Sources of Electric Energy
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BEE 3243 Electric Power Systems – Module 1
Modern Electric Power Systems
A modern complex interconnected power system can be subdivided into 4 major parts:Generation
Transmission & Subtransmission
Distribution
Loads
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BEE 3243 Electric Power Systems – Module 1
Generation• Generators 3-phase ac synchronous generator or alternator. Have 2 rotating fields – rotor (synchronous speed and
excited by dc current) & stator windings (3-phase armature current).
Size of generators – 50 MW to 1500 MW. Mechanical power – prime mover (hydraulic turbines,
steam turbines, gas turbines). Steam/ Gas turbines – high speeds, 1800/ 3600 rpm. Hydraulic turbines – low speed, 150 – 300 rpm.
Modern Electric Power Systems
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BEE 3243 Electric Power Systems – Module 1
Modern Electric Power Systems
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BEE 3243 Electric Power Systems – Module 1
• Transformers Step-up transformers are used to increase the voltage
level for long distances power transmission. The power transferred to the secondary is almost the
same as the primary. In modern utility system, the power may undergo 4 or 5
transformations between generator and ultimate user.
Modern Electric Power Systems
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BEE 3243 Electric Power Systems – Module 1
Modern Electric Power Systems
Transformer at Kenyir
Dam Hydroelectric
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BEE 3243 Electric Power Systems – Module 1
Transmission and Subtransmission Transfer electric energy from generating units at various
locations to the distribution system. Transfer of power between regions during emergencies. In Malaysia, transmission voltage are standardized at 66
kV, 132 kV, 275 kV, and 500 kV line-to-line. Subtransmission connects the HV substation through
step-down transformers to the distribution substation. Typical subtransmission voltage level ranges from 66 kV
to 132 kV. Capacitor banks/ reactor banks are used to maintain the
transmission line voltage.
Modern Electric Power Systems
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BEE 3243 Electric Power Systems – Module 1
Modern Electric Power Systems
Step Down Transformer at Subtransmission Network
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BEE 3243 Electric Power Systems – Module 1
Distribution The primary distribution lines are ranging from 6.6 kV to 33
kV. The secondary distribution lines are normally at 415 V and
240 V. Distribution systems are both overhead and underground.
Modern Electric Power Systems
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BEE 3243 Electric Power Systems – Module 1
Loads Divided into industrial, commercial, and residential. Very large industrial loads may be served from the
transmission system. Industrial loads – mostly induction motors. Commercial & residential loads – lighting, heating, and
cooling. Greatest value of load during a 24-hr period is called peak or
maximum demand. Daily Load factor = average load X 24 hr/ peak load X 24 hr.
Modern Electric Power Systems
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BEE 3243 Electric Power Systems – Module 1
National Grid, Malaysia
• National Grid is the primary electricity transmission network linking the electricity generation, transmission, distribution and consumption in Malaysia.
• It is operated and owned by Tenaga Nasional Berhad (TNB).
• More than 420 substations in Peninsular Malaysia are linked together by the extensive network of transmission lines operating at 132, 275 and 500 kilovolts (kV).
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BEE 3243 Electric Power Systems – Module 1
National Grid, Malaysia
• The power generation capacity connected to the National Grid is 18,391 MW.
• The generation capacity is about :82% : thermal power stations 18% : hydroelectric power stations.
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BEE 3243 Electric Power Systems – Module 1
National Grid, Malaysia
• Listed below are the power connected to the Malaysian National Grid on Malaya:
• Tenaga Nasional – with 11,296 MW installed capacity
• Malakoff – with 4,393 MW installed capacity • Powertek – with 1,490 ME installed capacity
• YTL Power – with 1,212 MW installed capacity.
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BEE 3243 Electric Power Systems – Module 1
National Grid, Malaysia
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BEE 3243 Electric Power Systems – Module 1
National Grid, Malaysia
Tenaga Nasional Berhad • Tenaga Nasional Berhad is the largest
electricity utility company in Malaysia and also the largest power company in Southeast.
• TNB's core activities are in the generation, transmission and distribution of electricity.
• The TNB Group has a generation capacity of 11,296 MW.
• TNB generates electricity mainly from two major types of plant; hydroelectric plants and thermal plants.
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BEE 3243 Electric Power Systems – Module 1
Representation of EPS
One-line Diagram
BY
R
3-phase system single-phase system
One-line diagram is a simplified single-phase circuit diagram of a balanced three-phase electric power system.
It is indicated by a single line and standard apparatus symbols.
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BEE 3243 Electric Power Systems – Module 1
Representation of EPS
Apparatus Symbols of One-line Diagram
Machine or rotating armature
Two-winding power transformer
Three-winding power transformer
Power circuit breaker, oil/ liquid
Air circuit breaker
Load
Or
Or
Or
Or
Cont…
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BEE 3243 Electric Power Systems – Module 1
Representation of EPS
Apparatus Symbols of One-line Diagram
A
VOr
Current transformer
Busbar
Transmission line
Fuse
Potential transformer
Three-phase, three-wire delta connection
Three-phase wye, neutral ungrounded
Three-phase wye, neutral grounded
Ammeter
Voltmeter
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BEE 3243 Electric Power Systems – Module 1
Representation of EPS
One-line DiagramThe information on a one-line diagram is vary according to the problem at hand and the practice of the particular company preparing the diagram.
Load/ Power Flow Study
Transient Stability Study
Example :
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BEE 3243 Electric Power Systems – Module 1
Advantages of One-line Diagram Simplicity. One phase represents all three phases of the balanced
system. The equivalent circuits of the components are replaced
by their standard symbols. The completion of the circuit through the neutral is
omitted.
Representation of EPS
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BEE 3243 Electric Power Systems – Module 1
Representation of EPS
Impedance and Reactance Diagrams Impedance (Z = R + jX) diagram is converted from one-
line diagram showing the equivalent circuit of each component of the system. It is needed in order to calculate the performance of a system under load conditions (Load flow studies) or upon the occurrence of a short circuit (fault analysis studies).
Reactance (jX) diagram is further simplified from impedance diagram by omitting all static loads, all resistances, the magnetizing current of each transformer, and the capacitance of the transmission line. It is apply to fault calculations only, and not to load flow studies.
Impedance and reactance diagrams sometimes called the Positive-sequence diagram.
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BEE 3243 Electric Power Systems – Module 1
1
2
3
Load B
T2T1
Load A
Representation of EPS
Impedance and Reactance Diagrams
Example : One-line diagram of an electric power system
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BEE 3243 Electric Power Systems – Module 1
E1 E2 E3
Gen. 3
Load B
Transformer T2
Transmission Line
Transformer T1
Load A
Generators 1 and 2
Impedance diagram corresponding to the one-line diagram of Example 1.2
Representation of EPS
Impedance and Reactance Diagrams
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BEE 3243 Electric Power Systems – Module 1
Reactance diagram corresponding to the one-line diagram of Example 1.2
E1 E2 E1
Generators 1 and 2
Transmission Line
Transformer T2
Gen. 3
Transformer T1
Representation of EPS
Impedance and Reactance Diagrams
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BEE 3243 Electric Power Systems – Module 1
Representation of EPS
Per-unit Representation Common quantities used in power system analysis are
voltage (kV), current (kA), voltamperes (kVA or MVA), and impedance (Ω).
It is very cumbersome to convert currents to a different voltage level in a power system having two or more voltage levels.
Per-unit representation is introduced such that the various physical quantities are expressed as a decimal fraction or multiples of base quantities and is defined as:
quantity of valuebase
quantity actualunit-perin Quantity
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BEE 3243 Electric Power Systems – Module 1
Representation of EPS
Example :
For instance, if a base voltage of 275 kV is chosen, actual voltages of 247.5 kV, 275 kV, and 288.75 kV become 0.90, 1.00, and 1.05 per-unit.
For simplicity, per-unit is always written as pu. For single-phase systems:
11
11
1
2LN
LN
LN
1
MVA baseMW power, Base
kVA basekW power, Base
MVA base
)kV voltage,(baseimpedance Base
A current, base
V voltage,baseimpedance Base
kV voltage,base
kVA baseA current, Base
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BEE 3243 Electric Power Systems – Module 1
Representation of EPS
33
33
3
2LL
LL
3
MVA baseMW power, Base
kVA basekW power, Base
MVA base
)kV voltage,(baseimpedance Base
kV voltage,base X 3
kVA baseA current, Base
For three-phase systems:
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BEE 3243 Electric Power Systems – Module 1
Representation of EPS
Example :
A three-phase, wye-connected system is rated at 100 MVA and 132 kV. Express 80 MVA of three-phase apparent power as a per-unit value referred to
(a) the three-phase system MVA as base and
(b) the single-phase system MVA as base.
(a) For the three-phase base,
Base MVA = 100 MVA = 1 pu
and Base kV = 132 kV (LL) = 1 pu
so Per-unit MVA = 80/100 = 0.8 pu
(b) For the single-phase base,
Base MVA = 1/3 X 100 MVA = 33.333 MVA = 1 pu
and Base kV = 132/√3 = 76.21 kV = 1 pu
so Per-unit MVA = 1/3 X 80/33.333 = 0.8 pu
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BEE 3243 Electric Power Systems – Module 1
Representation of EPS
Changing the Base of Per-unit Quantities The impedance of individual generators and
transformers are generally in terms of % or pu quantities based on their own ratings (By manufacturer).
For power system analysis, all impedances must be expressed in pu on a common system base. Thus, it is necessary to convert the pu impedances from one base to another (common base, for example: 100 MVA).
Per-unit impedance of a circuit element
2kV) voltage,(base
MVA) (base X ) impedance, (actual
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BEE 3243 Electric Power Systems – Module 1
Representation of EPS
old
new
2
new
oldoldnew MVA base
MVA base
kV base
kV baseunit Z-perunit Z-Per
The equation shows that pu impedance is directly proportional to base MVA and inversely proportional to the square of the base voltage.
Therefore, to change from old base pu impedance to new base pu impedance, the following equation applies:
Example 1.5:
The reactance X” of a generator is given as 0.20 pu based on the generator’s nameplate rating of 13.2 kV, 30 MVA. The base for calculations is 13.8 kV, 50 MVA. Find X” on this new base.
pu 306.030
50
13.8
13.20.20x"
2
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BEE 3243 Electric Power Systems – Module 1
Representation of EPSExample :
A 30 MVA 13.8 kV three-phase generator has a subtransient reactance of 15%. The generator supplies two motors over a transmission line having transformers at both ends, as shown in the one-line diagram below. The motors have rated inputs of 20 MVA and 10 MVA, both 12.5 kV with x” = 20%. The three-phase transformer T1 is rated 35 MVA, 13.2Δ – 115Y kV with leakage reactance of 10%. Transformer T2 is composed of three single-phase transformers each rated at 10 MVA, 12.5Δ – 67Y kV with leakage reactance of 10%. Series reactance of the transmission line is 80 Ω. Draw the reactance diagram with all reactances marked in per unit. Select the generator rating as base in the generator circuit.
Cont…
1
2
(13.8 kV)
k n(120 kV)
l mT1 T2
p
r
(12.9 kV)
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BEE 3243 Electric Power Systems – Module 1
Representation of EPSThe three-phase rating of transformer T2 is 3 X 10 MVA = 30 MVA.
and its line-to-line voltage ratio is 12.5 – √3 X 67 = 12.5 – 116 kV.
A base of 30 MVA, 13.8 kV in the generator circuit requires a 30 MVA base in all parts of the system and the following voltage bases:
In transmission line: 13.8(115/13.2) = 120 kV.
In motor circuit: 120(12.5/116) = 12.9 kV.
The reactances of the transformers converted to the proper base are:
Transformer T1: X = 0.1 (13.2/13.8)2(30/35) = 0.0784 pu.
Transformer T2: X = 0.1(12.5/12.9)2 = 0.0940 pu.
The base impedance of the transmission line is
(120 kV)2/30 MVA = 480 Ω
and the reactance of the line is (80/480) = 0.167 pu.
Reactance of motor 1 = 0.2 (12.5/12.9)2(30/20) = 0.282 pu.
Reactance of motor 2 = 0.2 (12.5/12.9)2(30/10) = 0.563 pu.
Cont…
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BEE 3243 Electric Power Systems – Module 1
Representation of EPS
Eg Em2Em1
jo.15
j0.0784 j0.167 j0.0940
j0.282 j0.563
p r
nmlk
Reactance diagram :
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BEE 3243 Electric Power Systems – Module 1
Basic Computer Analysis of EPS
For a power system to be practical, it must be safe, reliable, and economical. Hence, many analyses must be performed to design and operate a power system.
However, the pre-requisite before the analyses can be performed is the modelling tasks – to model all components of electric power systems.
The modelling and analysis of a power system require the aid of PC.
The basic analyses of an electric power system are:– Load flow/ power flow analysis.– Fault analysis.– Stability analysis (steady state, dynamic , and transient
stabilities).
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BEE 3243 Electric Power Systems – Module 1
Basic Computer Analysis of EPS
Load Flow / Power Flow A load flow study is the steady-state solution of an
electric power system for determination of the voltage, current, power (both active, P and reactive power, Q), and power factor at various points in the network.
Load flow studies are the backbone of power system analysis and design such as planning, operation, economic scheduling, transient stability and contingency studies.
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BEE 3243 Electric Power Systems – Module 1
Fault Analysis Fault studies concern about the determination of bus
voltage and line currents during various types of faults. Faults occur in power system due to: (1) Insulation failure in the equipments.
(2) Flashover of transmission lines initiated by lightning stroke.
(3) Mechanical damage to conductors and tower.
(4) Accidental faulty operation.
Faults are divided into three-phase balanced faults and unbalanced faults (single line-to-ground fault, line-to-line fault, and double line-to-ground fault).
The relative frequency of occurrence of various faults are 3-Φ fault (5%), double line-to-ground fault (10%), line-to-line fault (15%), and 1-Φ to ground fault (70%).
Basic Computer Analysis of EPS
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BEE 3243 Electric Power Systems – Module 1
Basic Computer Analysis of EPS
Stability Analysis Because the power system stability is an electro-
mechanical phenomena, it is thus defined as the ability of designated synchronous machines in the system to remain in synchronism with one another following disturbances such as fault and fault removal at various locations in the system.
Three types of stability are of concern: steady state, dynamic, and transient stability. Steady state stability relates to the response of a synchronous machine to a
gradually increasing load. Dynamic stability involves the response to small disturbances that occur in the
system, producing oscillation. Also known as small signal stability. Transient stability involves the response to large disturbances, which may cause
rather large changes in rotor speeds, power angles, and power transfer.
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