Power System Lecture Notes

lecture notes on power system operation and control and lecture notes on power system transients pdf free download
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VEER SURENDRA SAI UNIVERSITY OF TECHNOLOGY BURLA, ODISHA, INDIA DEPARTMENT OF ELECTRICAL ENGINEERING Power System-I Lecture Notes Subject Code: BEE1507 Lecture Notes Power System-I Syllabus MODULE-I (10 HOURS) Introduction to different sources of energy and general discussion on their application to generation,general introduction to power transmission by DC and AC overhead lines & underground cables, Perunit system, Single line diagram Choice of size and number of generating units: Review of the terms maximum demand, load factor,diversity factor, plant capacity and use factor, load & load duration curve and their effect on thegenerating capacity. Reserve units (hot, cold and spinning- reserve), different types of power tariffs,brief idea about national grid and its operational problems. MODULE-II (10 HOURS) Hydro plant: classification of plants, base load and peak load station, Turbines, head gate, penstock,surge tank, scroll case, draft tube and tail race, power plant auxiliaries. Thermal Power: Block diagrams, Boilers, steam turbines, super heater, economizer, air preheater, dustcollection, draft fans and chimney; condensers, feed water heaters, cooling water system; Governors,plant layout and station auxiliaries. MODULE-III (10 HOURS) Nuclear Power: Fission & fusion, reactor construction, controlled chain reaction, operational controlof reactors, Reactors (Boiling water, pressurized water, sodium graphite, breeder), layout of nuclearpower plant. Electrical System: excitation system, AVR: magnetic amplifier and thyristor converter type/DVR.Main transformer, unit transformer and station reserve transformer, commissioning tests of alternatorsand transformers. MODULE-IV (10 HOURS) Substation & Earthing: Types of substations, arrangement of bus-bars and control equipments, solidearthing, resistance earthing and Peterson coil,Distribution System; types of distributors and feeders (radial & ring), voltage drop and loadcalculation, Primary and secondary distribution network, Capacitor placement in distribution network,Distribution system planning, Service area calculation. Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 3 Lecture Notes Power System-I Important Terms Demand Factor = Maximum Demand / Connected Load Connected Load: sum of continuous ratings of all outlets in a distribution circuit Maximum Demand: maximum power that the distribution circuit is likely to draw at any time Group Diversity Factor = Sum of individual maximum demands / Maximum demand of the group GDF is always greater than unity Peak Diversity Factor =sum of maximum demand of a consumer group / demand of the consumer group at the time of maximum demand Load Factor =Average Load / Peak Load Capacity Factor = Average Demand / Installed Capacity Utilization Factor = Maximum Load / Rated Plant Capacity Load Curve: It is the curve between load (MW) versus time. Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 15 Lecture Notes Power System-I Load Duration Curve: It is the rearrangement of all the load elements of a load curve in a descending order plotted as a function of time. Energy Load Curve: It plots the cumulative integration of area under the load curve. Mass Curve It gives the total energy used by the load up to each hour of the day. Figure 1: Load Curve Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 16 Lecture Notes Power System-I Figure 2: Load Duration Curve Figure 3: Domestic Load (DF=0.5) Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 17 Lecture Notes Power System-I Figure 4: Industrial Load (DF=0.8) Figure 5: Commercial Load Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 18 Lecture Notes Power System-I Operating Reserves  How much generating capacity should be committed and how much should be left for future expansion?  In electricity networks, the “operating reserve” is the generating capacity available to system operator within a short interval of time to meet the changing demand or in case a generator is out of service. Table 2: Operating Reserves Spinning Reserve Non-spinning Reserve (Hot Reserves) (Cold Reserves) It is the extra generating capacity that is It is the reserve which can be brought ONLINE available by increasing the power output of the after a short delay. It also includes imported generator that are already connected to power power. system. In other words, it is the unloaded generation In other words, cold reserve is the reserve i.e. synchronized and ready to serve the generating capacity that is available for service additional demand. but not in operation. Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 19 Lecture Notes Power System-I Tariffs Objectives  Capital recovery  Operational cost of distribution utility  Cost of metering, billing and collection  Simple and comprehensible to general public  Uniform for a large population  Should provide incentives for using power in off-peak hours  Should have a provision of penalty for low power factor. General Tariff Form A = cx + dy + f Where A= total amount of bill for a certain period x=maximum demand during a period (kW or kVA) y= total energy consumed during the period in kWh c=unit charge for maximum demand (Rs/kWh or Rs/kVA) d=unit cost of energy (Rs/kWh) f= constant charge Flat Demand Rate A = cx Straight Meter Rate A = dy Block Meter Rate A=d1y1 +d2y2 + … Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 20 Lecture Notes Power System-I Spot Pricing  It is the half hour price of whole sale electricity market.  The spot price is published by the pricing manager for each point of connection on the national grid.  The electricity market uses spot electricity prices for each trading period to schedule available generation so that the lowest cost generation is dispatched first. Availability based Tariff It is a frequency based pricing mechanism for electric power. The ABT falls under electricity market mechanisms to charge and regulate power to achieve short term and long term network stability as well as incentives and disincentives to grid participants against interruption in committed supplies. National Grid Table 3: Grids in India  From 2006, all the northern grids connected to form central grid  Since 2013, the southern and central grid unified, but not fully. Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 21 Lecture Notes Power System-I Module-2 Hydro Power Potential P = gρQH Where P = Power available in water 2 g = 9.81 m/s 3 Q = flow or discharge (m /s) H = Height of fall of water or head (m) -3 P = 9.811000QH10 kW = 9.81 QH kW P= 9.81 QHη kW where η = efficiency of the turbine-generator assembly  Rain falling on earth’s surface has potential energy relative to oceans.  This energy is converted to shaft work when the water falls through a vertical distance.  This shaft work is used to drive water turbines to generate electricity. Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 22 Lecture Notes Power System-I Hydrology • First requirement – Q (discharge) • Hydrology deals with occurrence and distribution of water over and under earth’s surface. – Surface Water Hydrology – Ground Water Hydrology • Watershed, catchment area or drainage area: length of the river, size and shape of the area it affects, tributaries, lakes, reservoirs etc. • Investigation of run-off for past few years is required for power potential studies of a HPP. Objectives of Hydrology • To obtain data regarding the stream flow of water that would be available, • To predict the yearly possible flow • To calculate the mean annual rainfall in the area under consideration from a record of the annual rainfall for a number of years, say 25 to 30 • To note the frequency of dry years • To find maximum rainfall and flood frequency Various terms related to Hydrology • Rainfall is also known as precipitation and can be measured by rain gauges. • Some part of precipitation is lost due to evaporation, interception and transpiration. • Transpiration: Plants absorbing moisture and giving it off to the atmosphere • Stream flow = precipitation – losses • Stream flow = surface flow + percolation to ground • Surface flow is also known as run-off. • Hydrograph: 3 – shows the variation of stream flow in m /s with time for a particular river site. The time may be hour, week, month or a year. – The area under hydrograph gives the total volume of flow Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 23 Lecture Notes Power System-I • Flow duration curve: – shows the percentage of time during the period when the flow was equal to greater than the given flow. – The area under FDC gives the total quantity of run-off during a period • Mass curve – indicates the total volume of run-off in cubic meters up to a certain time. – the slope of the curve at any point shows the rate of flow at that time – Used for estimating the capacity of storage reservoir • Storage: – to ensure water availability during deficient flow and thus increasing the firm capacity – Storage also results in more energy production • Pondage: – Storing water in small ponds near the power plant as the storage reservoir is away from plant – To meet the power demand fluctuations over a short period of time e.g. 24 hours • Primary Power: power that will be available 90 % of the time • Secondary Power: power that will be available 75 % of the time • Dump Power: power that will be available 50 % of the time. • Maximum flow estimation: gives estimation of floods and helps in design of dam and spillway. Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 24 Lecture Notes Power System-I Site Selection for Hydropower Plants • Availability of Water: Run-off data for many years available • Water Storage: for water availability throughout the year • Head of Water: most economic head, possibility of constructing a dam to get required head • Geological Investigations: strong foundation, earthquake frequency is less • Water Pollution: excessive corrosion and damage to metallic structures • Sedimentation: capacity reduces due to gradual deposition of silt • Social and Environmental Effects: submergence of areas, effect on biodiversity (e.g. western ghat), cultural and historic aspects • Access to Site: for transportation of construction material and heavy machinery new railway lines or roads may be needed • Multipurpose: power generation, irrigation, flood control, navigation, recreation; because initial cost of power plant is high because of civil engineering construction work Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 25 Lecture Notes Power System-I Types of Dams Figure 6: Earth and Rockfill Dam Figure 7: Arc Dam Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 26 Lecture Notes Power System-I Figure 8: Arc Gravity Dam Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 27 Lecture Notes Power System-I Classification of Hydropower Plants According to water flow regulation: 1. Runoff river plants without pondage 2. Runoff river plants with pondage 3. Hydroelectric plants with storage reservoir According to Load: 1. Base load plants 2. Peak load plants 3. Pumped storage plants According to head: 1. High head plants (100m) 2. Medium head plants (30-100 m) 3. Low head plants (30 m) Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 28 Lecture Notes Power System-I Components of a HPP Figure 9: Schmatic of a Hydropower Plant The various components of HPP are as follows: 1. Catchment area 2. Reservoir 3. Dam 4. Spillways 5. Conduits 6. Surge tanks 7. Draft tubes 8. Power house 9. Switchyard for power evacuation Dam  Develops a reservoir to store water  Builds up head for power generation Spillway  To safeguard the dam when water level in the reservoir rises Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 29 Lecture Notes Power System-I Intake  Contains trash racks to filter out debris which may damage the turbine Forebay  Enlarged body of water just above the intake Figure 10: Forebay Conduits  Headrace is a channel which lead the water to the turbine  Tailrace is a channel which carries water from the turbine  A canal is an open waterway excavated in natural ground following its contour.  A flume is an open channel erected on a surface above ground.  A tunnel is a closed channel excavated through an obstruction.  A pipeline is a closed conduit supported on the ground.  Penstocks are closed conduits for supplying water “under pressure” from head pond to the turbines. Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 30 Lecture Notes Power System-I Figure 11: Forebay with Penstock Figure 12: Penstocks Surge Tank  A surge tank is a small reservoir in which the water level rises or falls to reduce the pressure swings so that they are not transmitted to the penstock.  Water Hammer o Load on the turbine is suddenly reduced Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 31 Lecture Notes Power System-I o Governor closes turbine gates o Sudden increase of pressure in the penstock  Negative Pressure o Load on the generator is suddenly increased o Governor opens the turbine gates o Tends to cause a vacuum in the penstock  When the gates are closed, water level rises in the surge tank and when the gates are suddenly opened, surge tank provides the initial water supply. Figure 13: Surge Tank Draft Tubes The function of the draft tube is to  To reduce the velocity head losses of the water  To allow the turbine to be set above the tailrace to facilitate inspection and maintenance Department of Electrical Engineering, Veer Surendra Sai University of Technology Burla Page 32

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