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# Power system planning & operation [eceg 4410]

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### Power system planning & operation [eceg 4410]

1. 1. Ayele Nigussie
2. 2.  Accurate electric load forecasting is crucial forpower system planning and operation. The forecasted load should be close to the loaddemand on the power system. Load forecasting is always associated with someuncertainty. Power systems, however, are to be planned insuch a way that changing load developments canbe accommodated by the expansion of the system.
3. 3.  load forecasting helps a company to decide◦ Purchasing electric power◦ Generating electric power◦ Load switching◦ Infrastructure development Three types of forecasts:1. short-term forecasts- which are usually from one hourto one week2. Medium-term forecasts- which are usually from aweek to a year3. long-term forecasts- which are longer than a year
5. 5.  The precise application of the different methodscannot be determined exactly. And combinations of the methods are usuallyapplied.
6. 6.  This method is based on the existing load and theincrease in the previous years and estimates thefuture load increase by means of exponentialincrease: s=rate of increase per year P0 = previous load Pn=load at the nth year n=year
7. 7.  This method is simple but cannot considerexternally measured variables and is hardlysuitable to provide reliable load and energypredictions.Example: Assume the pick load on Haramaya substation is 5MW and the annual growth rate is 7%. What willbe the pick load after 10 solid years? Ans: P10=9.84 MW
8. 8.  An increase in accuracy is obtained if the loadforecast is carried out separately for the individualconsumption sectors, such as households,commercial, public supply and industrial sectors. Then the individual results are summed for eachyear to obtain the total system load. Another model for load forecasting is based on thephenomenological description of the growth ofelectrical energy consumption as shown next:
9. 9.  With this model, adjustments can be combined withthe process of load development of the past withdifferent increases and saturation effects for the future.
10. 10.  Load forecast calculated with the loaddevelopment model (curves for various values of kand l ).
11. 11.  As the economy of a country grows, so does thepower demand. Load forecast with economic characteristic dataobtained from energy statistics assumes differentrelations between economic growth, availability ofenergy resources, energy consumption andrequirements in general, such as the increase inenergy consumption due to growth of population, andin special applications, such as energy requirementsof industry.
12. 12.  The requirement for electrical energy per capita of thepopulation is determined to a large extent by the standard ofliving and the degree of industrialization of a country. However, high consumption of energy can be also anindicator of high waste of energy. The increase of electrical energy consumption inindustrialized countries is less affected by the growth ofpopulation and predominantly by the growth of the grossdomestic product ( GDP ) and/or the gross national product (GNP ).
13. 13. Example: In the GTP, the GDP of Ethiopia is supposed to grow at 15%.Before the GTP period, the power demand was growing at arate of 23% (GDP growth=11%). Assuming a direct relationshipbetween the economy and the power demand,a. What is the rate of power demand growth in the GTP period?b. In 2002 E.C, the national power demand was approximately1500 MW. What will be the expected power demand in 2007E.C?
14. 14.  In power system expansion, development plan isvital in forecasting the power requirement. For instance, we can use the table on the nextslide in power system planning.
15. 15. Example: Near Addis, a business area of 10km-squared is to beelectrified. Forecast the power demand. Land development plans contain general informationabout the area development and use of land, and thesize, location and types of residential, industrial andcommercial areas, without allowing one to be able toderive detailed individual measures from them.
16. 16.  Another way of load forecasting is based on theannual energy consumption of individual consumer orconsumer groups, which can be taken from the annualelectricity bill. The system load can be determined by means ofstandardized load curves for different consumergroups such as◦ Residential◦ Commercial◦ Public sectors◦ industrial
17. 17.  As consumption profiles of the particular customergroups not only change with time of day but also showday - of - week and seasonal changes, characteristicdays are defined, such as working - day, Saturday,Sunday (or Friday in Islamic countries) and holiday aswell as seasonal differences in winter, summer andtransition periods. Based on the load curves we can forecast the future loadfor a particular hour, a particular day and a particularyear.
18. 18.  Summer sunday
19. 19.  Summer working day
21. 21.  Nowadays, fuzy logic, ANN, and other algorithmsare used in power system planning to forecastload. These algorithms have artificial learningcapabilities. And thus, by taking the past into consideration,they can predict the future.
22. 22. Planning and Design of hydro generationstationsAyele Nigussie
23. 23. 1. Introduction2. Layout3. Environmental Effects of HPPs4. Economic Aspects of HPPs5. Designing HPPs6. Summary
24. 24.  Hydroelectric power captures the energy releasedfrom falling water. Potential Energy  Kinetic energy  ElectricalEnergy Hydroelectric power plants are categorized as◦ Micro hydropower plants [<100 kW)◦ Mini Hydropower Plants [100 kW – 1 MW]◦ Small Hydropower Plants [1 MW – 30 MW]◦ Large Hydropower Plants [>30 MW] In Ethiopia, more than 96% of the electricity is hydro.
25. 25.  The effects are: Physical -◦ change the ecosystem,◦ effect on downstream,◦ Loss of habitat◦ Loss of farms◦ Deforestation◦ Effect on micro-climate level Biological-◦ Flora◦ Fauna◦ Humans
26. 26.  High initial cost of construction. Electricity is cheap. Energy is green. In an HPP construction, costs to be considered:◦ land/land rights,◦ structures and improvements,◦ equipment, reservoirs, dams, waterways, roads, railroads, andbridges.◦ protecting fish and wildlife.◦ Operation and maintenance costs◦ hydraulic expenses, electric expenses, and rents.
27. 27.  When designing a hydroelectric power plant a number ofelements and equipment need to be taken intoconsideration. Dam size, retention basin size and depth, inlet valves,weir and control gates, penstock length and diameter,turbines, generators, transformers and excitationequipment, and efficiency all have to be examined. Elevation or head and stream flow have to beestablished as well.
28. 28.  Firm power:
29. 29.  Based on the firm power:◦ Mechanical Engineers design the hydraulicturbines.◦ Electrical engineers design the generators,transformers, the switch yards and theprotection system.◦ Dams, canals, intakes, penstocks, tailraces andpower houses are designed by civil engineers. Firm power is also one of the main factors thatdecides the feasibility of an HPP.
30. 30.  Feasibility study contains:◦ Site visit and selection◦ Capacity analysis◦ Economic analysis◦ Environmental impact analysis Feasibility study is the first step in HPP construction.
31. 31.  In planning an HHP, the generalrequirements are:◦ Determining location of the powerhouse , location ofswitchyard ,◦ Laying out the highway and railroad access, other sitefeatures,◦ Determining types of powerhouse, structures,◦ selection of type of powerhouse,◦ location of main transformers, powerhouse andswitchyard, equipment, powerhouse Auxiliary Equipment
32. 32.  Architectural design requirements are:◦ Exterior Design◦ Exterior Details◦ Interior Design◦ Interior Details◦ Schedule of Finishes◦ Painting◦ Design memorandum◦ Drawings
33. 33.  The structural requirements are:◦ All the civil works are under this category.
34. 34. Ayele Nigussie
35. 35. 3.1 Introduction3.2 What is a substation?3.3 Important points3.4 Classification of substations3.5 Substation equipments3.6 Substation Configurations3.7 Substation design3.8 Planning of substations3.9 Conclusion
36. 36.  A substation is a nodal point in a powersystem. Internationally standardized voltage levelfor substations: 66 kV, 110 kV, 132 kV, 150 kV, 220kV, 380 kV, For very long transmission distances : 500kV, 800 kV
37. 37. Tasks of substation: Distribution of power towards load circuit Separation of different network groups (reductionof short circuit power) Coupling of different voltage level via powertransformers Measuring, signaling and monitoring of networkdata (e.g. U, I, P, Q, f)
38. 38. 3.2 What is aSubstation ?The assembly ofapparatus used tochange somecharacteristics (e.g.voltage, a.c. to d.c. ,freq,p.f. etc..) of electricalsupply is called asubstation.
39. 39.  It should be located at a proper site(i.e. atthe center of gravity of load). It should provide safe and reliablearrangement. It should be easily operated andmaintained. It should involve minimum capital costs.
40. 40. SubstationAccording to service requirement According to constructional feature
41. 41. According to Service requirement: Transformer Substation: Transformers are installed totransform voltage from one level to another as per needs. Switching Substations: This substations mean for switchingoperation of powerlines with out transforming the voltage. Power factor correction Substation: This substations areinstalled to increase the power factor to minimise losses. Frequency Changer Substation: This substations are installedwhere speed control of motors is required. Converting Substation: This substations convert a.c to d.c orvice versa. Industrial Substation: This substations are installed to supplypower only to an industries.
42. 42. According To Constructional Features: Indoor SubstationsIndoor Substations: In this substations, the apparatus areinstalled with in the substation building. Till 66 kV. Outdoor SubstationsOutdoor Substations: this substations are installed in open land.This substations are employed for voltage levels beyond 66k.v. Underground SubstationsUnderground Substations: This: This substations are installed underground in densely populated cities where cost of the land ismore. Pole-Mounted SubstationsPole-Mounted Substations: This substations are erected fordistribution of power in localities. This is employed fortransformers up to 250 kVA.). Foundation Mounted SubstationsFoundation Mounted Substations: This substations are installed3.4 Classification ofSubstation …
43. 43.  Busbar: is a conductor connectingpower line to substation equipment. Insulators & fittings: fix and isolate thebusbar system. Isolating Switch: is used fordisconnecting equipment formaintenance and repair.
44. 44.  Relays & Circuit Breaker: open andclose a circuit under normal and faultconditions. Power Transformers: are used insubstations to step up or step downthe voltages. Instrument Transformers: used formeasuring .
45. 45.  Metering & Indicating Instruments:used to watch over the circuitquantities. Power line carrier communicationsystems: used for SCADA. Coupling capacitors and wave traps
46. 46. AC/DC supply: is used for auxillaries and DC supply forrelay operation.Oil handling system: used for purifying oil frommoisture.Illumination: should be properly illuminated for safety.Compressed air system: for functioning of CB.Service bay: to carry the equipments to installation side.Fire extinguishers
47. 47. Lightning/Surge Arresters
48. 48.  Isolating switches:
49. 49. • Circuit Breakers3.5 Substation equipments…
50. 50. 3.5 Substation equipments…
51. 51. 3.5 Substation equipments…
52. 52. 3.5 Substation equipments…
53. 53. Piezoelectric motorsPiezoelectric motorsPiezo GeneratorsPiezo GeneratorsActuatorsActuatorsUltrasonic TransducersUltrasonic TransducersAnd many more…And many more…
54. 54. What are to be considered? Site selection Design of structures Design of foundation for transformers &structures(IE Rules 64) Control room building Cable trench & drainage Design of earthing Protection schemes & interlocks
55. 55. Conventional substations (AIS): Construction according to standardized minimaldistances (clearance) between phase and earth Normally used for outdoor substations, just in very fewcases used for indoor substations Based on single power system equipments◦ Replacement of single equipment by equipments from othermanufacturers is possible. Simple to expand (in case that space is not an issue) Excellent overview, simple handling and easy access
56. 56.  Minimum clearance in air according to IEC 61936-1
57. 57.  Minimum clearance in air according to IEC 61936-1
58. 58. Basis requirements for new substations: Optimal location of substations within power system (load flow, shortcircuit, customer requirements, long term planning, land space) Selection of substation design Calculation of short-circuit currents and long term development(ratings) Selection of power system requirements Adaption of design according to available space, fixing of busbarconfiguration (e.g. using wire conductor or tubular conductor) Detailed planning of: primary and secondary equipment, auxiliaryequipment, basement, steel structure, building, earthing system
59. 59.  You can find important standards for power systeminstallations: Planning and Design of a substation normally startswith the development of the electrical single linediagram. A single line diagram shows number of busbars andsubstation bays including the relevant equipment.
60. 60.  Selection of substation layout depends on◦ Its importance within the power system(power system reliability in case offailures and maintenance activities)◦ Power system operation
61. 61. Substation is the heart of apower system. Hence, itsdesign should be such that itwill provide continuous ,quality & desired power withsafety.
62. 62.  Read further on substations.
63. 63. THANK YOU
64. 64. Electrical Considerations for T.L. Design: Low voltage drop Minimum power loss for high efficiency ofpower transmission. The line should have sufficient currentcarrying capacity so that the power can betransmitted without excessive voltagedrop or overheating.
65. 65.  Conductivity of Conductor:R = ρ.L/A , orR = L/Ϭ. AWhere:L: Conductor length.A: Conductor cross sectional area.ρ: resistivityϬ: Conductivity (Ϭ= 1/ρ)
66. 66.  The conductor conductivity must be veryhighto reduce Conductor resistance R andhence reduce lossesPL= 3 I2.R
67. 67. Mechanical Considerations for T.L.Design: The conductors and line supports shouldhave sufficient mechanical strength:- to withstand conductor weight, ConductorTension and weather conditions (wind,ice).- The Spans between the towers can belong.- Sag will be small.- Reducing the number and height of towersand the number of insulators.
68. 68. • Heat expansion coefficient must be verysmall.Rt = R0. (1 + α0 .t)αt = α0/(1+ α0.t)α t is the heat expansion coefficient at t.
69. 69. TYPES OFCONDUCTORSMATERIALS
70. 70. lowest cost – low mechanicalstrengthUsed for small span
71. 71. 1- Steel strands2- Aluminum strandsACSR (26/7)
72. 72. • High mechanical strength can be utilizedby using spans of larger lengths.• A reduction in the number of supports alsoinclude reduction in insulators and the riskof lines outage due to flash over or faultsis reduced.• losses are reduced due to larger diameterof conductor.• High current carrying capacity.
73. 73.  Wooden Poles Reinforced Concrete Poles Steel Poles Lattice Structure Steel Towers
74. 74. Wooden Poles
75. 75. Reinforced Concrete Poles
76. 76. Steel Poles
77. 77. 1- Suspension Tower2- Tension Tower3- Angle Tower4- End Tower
78. 78. This type of towers exist in the beginningand at the end of the line which exposedto tension in one side.
79. 79. Sag of T.L depends on:- Conductor weight.- Span length,- Tension in the conductor, T- Weather conditions (wind , ice).- Temperature.
80. 80. kV C (m)0.4 5.511 5.533 6.066 6.2132 6.2220 7.0400 8.4
81. 81. Spacing = (S )0.5+ V/150Where:S: Sag in meters.V: Line voltage in kV.
82. 82. Electrical Considerations for T.L. Design: Low voltage drop Minimum power loss for high efficiency ofpower transmission. The line should have sufficient currentcarrying capacity so that the power can betransmitted without excessive voltagedrop or overheating.
83. 83.  Conductivity of Conductor:R = ρ.L/A , orR = L/Ϭ. AWhere:L: Conductor length.A: Conductor cross sectional area.ρ: resistivityϬ: Conductivity (Ϭ= 1/ρ)
84. 84.  The conductor conductivity must be veryhighto reduce Conductor resistance R andhence reduce lossesPL= 3 I2.R
85. 85. Mechanical Considerations for T.L. Design: The conductors and line supports should havesufficient mechanical strength:- to withstand conductor weight, ConductorTension and weather conditions (wind, ice).- The Spans between the towers can be long.- Sag will be small.- Reducing the number and height of towers andthe number of insulators.
86. 86. • Heat expansion coefficient must be verysmall.Rt = R0. (1 + α0 .t)αt = α0/(1+ α0.t)α t is the heat expansion coefficient at t.
87. 87. TYPES OFCONDUCTORSMATERIALS
88. 88. lowest cost – low mechanicalstrengthUsed for small span
89. 89. 1- Steel strands2- Aluminum strandsACSR (26/7)
90. 90. • High mechanical strength can be utilizedby using spans of larger lengths.• A reduction in the number of supports alsoinclude reduction in insulators and the riskof lines outage due to flash over or faultsis reduced.• losses are reduced due to larger diameterof conductor.• High current carrying capacity.
91. 91.  Wooden Poles Reinforced Concrete Poles Steel Poles Lattice Structure Steel Towers
92. 92. Wooden Poles
93. 93. Reinforced Concrete Poles
94. 94. Steel Poles
95. 95. 1- Suspension Tower2- Tension Tower3- Angle Tower4- End Tower
96. 96. This type of towers exist in the beginningand at the end of the line which exposedto tension in one side.
97. 97. Sag of T.L depends on:- Conductor weight.- Span length,- Tension in the conductor, T- Weather conditions (wind , ice).- Temperature.
98. 98. kV C (m)0.4 5.511 5.533 6.066 6.2132 6.2220 7.0400 8.4
99. 99. Spacing = (S )0.5+ V/150Where:S: Sag in meters.V: Line voltage in kV.