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Production and distribution of electricity

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Lecture slides from my Production and distribution of electricity -course for Sustainable building engineering (SBE) students in Metropolia.

Lecture slides from my Production and distribution of electricity -course for Sustainable building engineering (SBE) students in Metropolia.

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  • http://www.abb.com/cawp/seitp202/c646c16ae1512f8ec1257934004fa545.aspxhttp://www.ieee-pes.org/enews-update/542-dc-vs-ac-the-second-war-of-currents-has-already-begun
  • http://en.wikipedia.org/wiki/File:COGAS_diagram.svg
  • http://en.wikipedia.org/wiki/File:PressurizedWaterReactor.gif
  • Source: Wikipedia
  • http://en.wikipedia.org/wiki/File:Boiling_water_reactor_english.svg
  • http://en.wikipedia.org/wiki/File:Pylon_ds.jpg
  • http://www.tukes.fi/fi/Rekisterit/sahko-ja-hissit-rekisterit/sahkotapaturmat/kuva-sahkotapaturmat/
  • http://www2.amk.fi/digma.fi/www.amk.fi/material/attachments/vanhaamk/etuotanto/5hNnu4mrg/tehomitoitus_asuinhuoneisto.pdf
  • http://upload.wikimedia.org/wikipedia/commons/e/ef/Schuko_plug_and_socket.png
  • http://www.tukes.fi/kodinsahkoturvallisuus/1_3.html
  • http://www.vernimmen.net/ftp/An_introduction_to_distributed_generation.pdf

Production and distribution of electricity Production and distribution of electricity Presentation Transcript

  • Production and Distribution ofElectricity http://www.flickr.com/photos/31119160@N06/8007585111/Vesa Linja-aho — Spring 2013
  • Technical details of the course Classes:  Mon 14:00-16:45 @ ETYA1124 (Leppävaara)  Wed 14:00-15:45 @ G406 (Kallio) Excursion: Ensto Group @ Porvoo, Tuesday 5 th of February 2013 at 10:00-12:40  We must depart at about 8:30 and we’ll be back at about 13:30, more information about transportation will follow later. The final exam is on Monday 25 th of February Attending the class is not mandatory, but highly recommended. All course material will be shared through Tuubi 2
  • About me Vesa Linja-aho, M. Sc. in electrical and electronics engineering. Professional background:  7 years at Aalto university (research and teaching)  1 year in Computerworld Finland magazine (editor)  3 years at Metropolia, senior lecturer in automotive electronics. firstname.lastname@metropolia.fi, +358404870869 My office is at Kalevankatu 43, Helsinki 3
  • We start with prerequisite exam 4
  • Why… is electric power usually generated in large plants instead of local generators? are high voltage levels used in power transmission and distribution? is alternating current used in power transmission and distribution? 5
  • It is fairly easy to distribute electricitywith low losses The distribution losses (from plant to end user), for distances of couple of hundreds of kilometers, are couple of percents (< 5 %). There are certain advantages with large-scale production of electricity  Emission control  Large electric machines have an efficiency near 100 %. 6
  • Homework Read the following article:  http://en.wikipedia.org/wiki/War_of_Currents We will discuss it on Monday 7
  • Homework Read the following article:  http://en.wikipedia.org/wiki/War_of_Currents We will discuss it on Monday 8
  • War of Currents Why was DC more common in the very early power systems? What inventions lead to the victory of AC? Why was DC transmission inferior to AC transmission? How about the future? Does DC have any advantages? 9
  • Three-phase system http://www.wolframalpha.com/input/?i=sin%28 2*pi*50*t%29%2C+sin%282*pi*50*t%2B2pi* %281%2F3%29%29%2C+sin%282*pi*50*t%2B 2pi*%282%2F3%29%29 Smooth power flow The currents cancel each other -> saves wiring material. Rotating magnetic field -> easy to design electric machines. 10
  • AC Pros  Easy to change the voltage level with transformers.  Arcing will cease automatically (zero-point) Cons  Ventricular fibrillation hazard  Losses via inductive and capacitive coupling 11
  • DC Pros  Low losses with long distances  Modern electronic and electric appliances use DC.  Many alternative power sources output DC  Easy to use with batteries Cons  Changing the voltage level is not simple  This is changing with development of power electronics.  Arcing hazard  Efficient electric generators produce AC by nature. 12
  • Second coming of DC? Using DC in buildings can result in 10-20 % savings. Solar panels, wind power, fuel cells, … Greater capacity for power lines Lower EMI. 13
  • The change is slow The life cycle of the main components (cables and transformers) is very long  For underground cables: 100 years  For transformers overhead power lines > 50 years. 14
  • How much? 110 kV overhead power line: 80 000 €/km 20 kV overhead power line: 20 000 €/km 110 kV / 20 kV substation: 0,5-3 M€ 15
  • How much power and how far? 110 kV: tens of megawatts for about 100 km. 20 kV: couple of megawatts for about 20-30 km. 16
  • The pricing The cost of the transmission is typically 15-50 % of the total price of the electricity. (average for consumers: 30 %). 17
  • What if I used a personal generator? Cost of fuel? Heat of Combustion? Cost of equipment? Efficiency? 18
  • Environmental aspects in distribution andtransmission of electricity Landscape protection Wood preservation agents Transformer oil leaks SF 6 in circuit breakers Noise 19
  • Landscape protection Where to put the power lines?  On open fields?  In the forest?  Next to roads?  Under ground?  20 kV:  uninsulated: 20 k€/km  coated: 26 k€/km  underground: 43-100 k€/km 20
  • Tricks for landscape protection When crossing a road, hide the poles in the forest. In hilly landscape, locate the line so that it’s silhouette is not against the sky. By using coated wires, the line can be made more compact and the wires can be camouflaged. 21
  • Wood preservation agents 20 kV and 110 kV lines usually have wooden poles (they are cheap). Preservation agents raise the life cycle of the poles from 10 years to over 50 years. Chrome, copper and arsenic (CCA) preservation agents are forbidden in new constructions and they are handled as toxic waste. Creosote oil is toxic also, but it is currently the best option Experimental: Pine oil and other oils. 22
  • Transformer oil Transformer oil is an insulator and coolant. Large substation transformers have a leakage pool under them, but small pole transformers do not (and they can contain 30-300 liters of oil). Leakage to ground water is a large risk, but oil leaks are very rare. In areas with ground water, dry and resin- insulated transformers can be used to eliminate the risk. 23
  • SF 6 - Sulfur hexafluoride Used as insulating agent in circuit breakers  very strong insulator  arc-suppressive  does not corrode switchgear Very strong greenhouse gas 24
  • Recycling of equipment Wires Poles Transformers 25
  • Noise 50 Hz / 60 Hz hum High voltage switchgear 26
  • Electric and magnetic fields Lot of research is done and AC electric power lines have existed for 100 years. The safety limits have a lot of overhead Currently:  there is no scientific evidence on harmfullness of low frequency fields (with low intensity)  same concerns the cell phone radiation 27
  • How to increase efficiency? Raise the voltage Use an extra 1 kV step in distibution (for distances of couple of kilometers). 28
  • Environmental aspects of ElectricityProduction Heat CO 2 Particles Accidents Water usage Nuclear waste Mining and refining Loss of land … 29
  • Most significant sources in the world Coal 41 % Natural Gas 21 % Hydroelectric 16 % Nuclear 13 % Oil 5 % Other 3 % 30
  • Renewable Hydroelectric 92 % Wind 6 % Geothermal 1,8 % Solar photovoltaic 0,06 % Solar thermal 0,004 % 31
  • Efficiency Depends greatly on the fact is the extra heat used for district heat or similar (cogeneration). For simple coal or nuclear power plant, the efficiency is about 33 %. For combined cycle gas turbine plants, the efficiency is over 50 %. If the waste heat is used for district heating, the total efficiency can be over 80 %. 32
  • Environmental aspects of ElectricityProduction Heat CO 2 Particles Accidents Water usage Nuclear waste Mining and refining Loss of land … 33
  • Most significant sources in the world Coal 41 % Natural Gas 21 % Hydroelectric 16 % Nuclear 13 % Oil 5 % Other 3 % 34
  • Renewable Hydroelectric 92 % Wind 6 % Geothermal 1,8 % Solar photovoltaic 0,06 % Solar thermal 0,004 % 35
  • Efficiency Depends greatly on the fact is the extra heat used for district heat or similar (cogeneration). For simple coal or nuclear power plant, the efficiency is about 33 %. For combined cycle gas turbine plants, the efficiency is over 50 %. If the waste heat is used for district heating, the total efficiency can be over 80 %. 36
  • Examples of power output Average electric power in world: 2,3 TW Average electric power in Finland: 10 GW Hoover Dam (1936): 2 GW Three Gorges Dam (2008): 22,5 GW Petäjäskoski (Finland’s largest HPP): 182 MW Kashiwazaki-Kariwa NPP: 8,2 GW Olkiluoto NPP 1,2 GW  Additional 1,6 GW in construction Inkoo CPP: 1 GW 37
  • Fossil fuel power generation Basic idea: burn something, generate steam for turbine. Efficiency: 33-48 % 38
  • Cogeneration, CHP combined heat&power Efficiency: over 80 %. 39
  • Combined cycle power plant Gas turbine + steam turbine. Efficiency over 60 % (even 90 % with CHP) 40
  • 41
  • Hydroelectric power plant Water rotates a turbine Efficiency little over 90 % 42
  • Nuclear power PWR (Pressurized water reactor) BWR (Boiling water reactor) Efficiency: about > 30 % 43
  • Pressurized water reactor PWR 44
  • Boiling water reactor (BWR) 45
  • Turbogenerators Large electric generators can achieve over 99 % efficiency , if cooled with hydrogen. Why hydrogen?  Low density  High specific heat and thermal conductivity Rotating speed: typically 3000 or 1500 rpm Output voltage typically 2-30 kV and output power up to 2 GW. 46
  • Elements of the transmission anddistribution system Substations  Transformers  Protective equipment Transmission and distribution lines 47
  • Transmission and distribution voltage 400 kV 220 kV 110 kV (45 kV) 20 kV (10 kV) (1 kV) 400 V (230 V between neutral and phase) 48
  • Other voltage levels in Finland 25 kV (railway overhead lines) 750 VDC (subway) 600 VDC (tram overhead lines) Estlink HVDC: 150 kV Fenno-Skan 1: HVDC: 400 kV Fenno-Skan 2: HVDC: 500 kV  Damaged by ship anchor Feb 2012  Estimated damage to electricity consumers: 80 M€ 49
  • 50
  • Insulators The length of the insulator is about 1 m / 100 kV 110 kV: 6-8 insulator disks 220 kV: 10-12 insulator disks 400 kV: 18-21 insulator disks 20 kV lines have usually small pin insulators, or couple of disks. Near the insulator, there are vibration suppression plates on the wire Insulators may have a thin conductive coating, for de-icing the insulators. Arcing horns protect the insulator from significant over voltage 51
  • Voltage drop in distribution In cities: 2-3 % In rural areas: 5 % According to SFS-EN 50160, the voltage can vary +6 %/-10 % (207-244 V). 52
  • Reliability 90 % of blackouts are caused by middle voltage network failures. Under 10 % are from low- voltage network. High-voltage network failures are very infrequent. Automatic fast reconnect typically solve 75 % of the failures. Delayed reconnect will solve 15 % of the failures and the remaining 10 % require repair work. 53
  • Electric safety in Finland Electric work is regulated  Typical: degree from vocational school + 1 year of experience.  Electric safety course every 5 years. In the company, a nominated head of electric work, who has  a degree (vocational, bachelor or master)  0.5-2 years of electric work experience  passed the electric safety examination 54
  • Three classes of electric qualification EQ 1 (general). EQ 2 (low-voltage). EQ 3 (low-voltage repair). 55
  • Electric deaths in Finland (moving average) non-professionals professionals 56
  • Electric deaths in Finland 2012  Electric shock from railway wire 2011  Electric shock from railway wire 2010  Young electrician died when measuring a newly built transmission line.  A person died from a shock from self- repaired extension cord.  Electric shock from railway wire. A detail: last time a small child has died in electric accident was in year 1996. 57
  • Most common causes for electric accidents Plain stupidity (railway wires) Self-made dangerous connections (protect earth misconnected). Professionals do not follow the safety regulations  Typical one: after disconnecting the voltage, the electrician does not verify that the installation is really dead. 58
  • Electric network in buildings Small buildings: 400 V / 230 V Larger buildings: own 20 kV transformer Industry: 110 kV input 59
  • Approximating the peak power: one way One way:  Lighting: 10 W/m 2  Appliances: 6 kW for < 75 m 2, 7,5 kW for > 75 m 2  + power of sauna  The other way:  Like the first, but appliances: 6 kW + 20 W/m 2 With electric heating:  the total maximum power heating power of the radiators, 3 kW for appliances 60
  • Structure of the network All wall sockets are grounded (since 1997). Three-wire system Wiring color system:  Black (or brown or purple or white) = live  Blue = neutral  Yellow-green: protect earth 61
  • Class I plug + socket 62
  • Protection systems Basic insulation (Class 0) Protect earth (Schuko) (Class I) Double insulation (Class II) 63
  • Basic protection The ”traditional” wall socket and plug. For new buildings, illegal since 1997. The appliances can be used. Problem: single insulation fault can make the chassis live. 64
  • Protect earth The chassis of the equipment is grounded If the PE wire is intact, there is no way the chassis would hold a dangerous voltage. Ground fault will blow the fuse 65
  • Safety insulation (Class II) All devices to be sold in EU are either Class I or Class II devices (or Class III with extra low voltage). In Class II, no single fault can make the chassis live. 66
  • RCD residual-current device (RCD) = residual- current circuit breaker (RCCB) = ground fault condition interrupter (GFCI), ground fault interrupter (GFI) or an appliance leakage current interrupter (ALCI) Monitors the current difference between live and neutral connectors. http://upload.wikimedia.org/wikipedia/common s/9/91/Fi-rele2.gif Mandatory in new installations (with certain exceptions) 67
  • Distributed production of electricity Centralized vs. distributed? 68
  • Benefits of centralized production Economics of scale Higher efficiency Low-loss transmission Reliability Environment (plants away from cities) 69
  • Why distributed production? Less pollution Better total efficiency More diverse energy source distribution Easier placement of power plants Back up generation Generation during power peaks Price level of power generators has decreased and will decrease 70
  • Distributed generation in EU (2004) 71
  • Less pollution ”Free” fuel (hydroelectric, wind) Production near the end user  less transmission losses. Easier cogeneration 72
  • Economic benefits Lower threshold for entering the market Modularity and easy expandability Faster construction Lower capital costs 73
  • Support from the state Subvention for production Tax relief Product development aid Obligation for network company to buy the electricity in fixed price. 74
  • Examples Small wind farm Small CHP for greenhouses Fuel cell, solar, combustion engine or microturbine plant 75
  • Challenges The network sees a generator as a negative load. The voltage at the end of the line will rise -> less losses.  Sizing of the wire can usually not be altered.  Very high power output can cause problem with overvoltage. The protection equipment should be aware of the generation. 76
  • Group work Article: Rural Electrification in Developing Countries. From book Lakervi, Partanen: Sähkönjakelutekniikka. 3. ed. 2008. Otatieto. Pp. 286—295. 77
  • Rural electrification (in developingcountries) Form three groups and each group will take one topic:  Social aspects in rural electrification  Economical aspects in rural electrification  Technical aspects in rural electrification Read from the article (about 20 minutes): intro + one of the chapters (area data, economical issues or technologies applied) It is great if your add aspects from your home country, was it industrialized or developing country. Write down your findings. After this, one will stay at the group and the others will go to next table. 78
  • Rural electrification in developingcountries About 4 billion people have access to electricity (of 7 billion people). Social impact. Economic impact. Environmental impact. 79
  • Conditions vary considerably Some relatively poor countries have high percentage in rural electrification (Costa Rica, Tunisia). 80
  • Area data Small houses + lamps = 100-200 W / person Refridgerators & TV:s = 400-500 W / person Electric heating of small houses = 1000-1500 W / person. If cooking is included = practically same as in industrialized countries. 81
  • Solutions Hydroelectric power, if available, is the best solution (almost zero maintenance). Diesel unit a popular choice. 82
  • Challenges Governmental intervention accelerate the electrification process. In turn, governmental intervention may include corruption. For sustainable distribution systems, a long- term financial balance is necessary. A well-functioning supply of electricity promotes social stability. 83
  • Challenges The wealthy demand high reliability and voltage stability. The poor demand low tariffs and fast progression of electrification. 84
  • Smart Grid Grid + modern automation technology + ICT = smart grid. Smart grid is a bunch of technologies to make grid more reliable, efficient and flexible. 85
  • History Electricity metering Dual tariff system 86
  • Problems with traditional grids How to cope with demand peaks?  Use peaking generators.  Black out certain areas.  Suffer from low power quality. Reliability in crisis situations:  Power distribution is pretty sensitive to terrorist attacks. Reading the electricity meters costs manpower. 87
  • Solutions Here already: smart metering. Dynamic demand management: for large customers. Real-time electricity pricing: in power peak, raise the price in real time until the demand sags. 88
  • Reliability Automatic fault detection and healing. 89
  • Efficiency Many high-power equipment work with duty cycle (they run with full power or are off). Example: many air conditioning units. Making these equipment demand-aware can reduce the peak power requirement without impact to the end user. Another example: a popular tv-show begins. Demand-aware tv sets would have small delay for powering on and they operate with reduced brightness, so that the power plants have time to increase their output. 90
  • Flexibility Traditional network protection gear is designed for one-way power flow. 91
  • Sustainability Large amounts of renewable energy need sophisticated network automation. For example, solar power output changes suddenly. 92
  • Charging electric vehicles When electric vehicles become more general, they will impact the sizing of the grid. During demand peaks, it is reasonable to pause the charging. 93
  • Concerns and challenges Privacy: who can access your electricity usage data? Complex tariff system – easy to unfairly trick the customers. Remote shutdown of electric supply. RF emissions (although not scientifically confirmed, people are afraid of them). Cyberterrorism Relatively high cost of investment 94
  • Asset management in electricitydistribution Grid development Grid maintenance Grid operation 95
  • Grid development process Based on the network strategy (environment, basic principles, present state, main measures for development) 96
  • The current state of the network Voltage drop Voltage elasticity (= how much does the voltage drop when adding more power demand to certain point). Loading of the wires Power losses Short circuit / earth fault currents Cost of power interruptions 97
  • Investment planning and prioritization If the yearly growth of the load is small, the driving factor for reconstruction is the useful life of the network components. The most important goal is to keep the grid to qualify the requirements of legislation. The task is a complex optimization process. 98
  • Grid maintenance Fixing maintenance Preventive maintenace  TBM = time based maintenance  CBM = condition based maintenance  RBM = reliability based maintenance 99
  • Reliability based maintenancec repairon overhauldit testi Service ifo necessaryn significance 100
  • Reliability based maintenance According to safety standards, overhead power lines must be inspected every 5 years. The inspection data is used to decide when to, for example, renew the pylons. 101
  • Examples of routine maintenance Clearance of the right-of-way of the power lines. Monitoring the oil temp of transformers Thermal imaging 102
  • Grid operation Grid operation = maintaining the short-term power quality, safety, customert service quality and economy. The operation is lead from control room  …which can be the operator’s laptop . The head of operation has very strict liability of the electric and work safety. 103
  • Main functions of grid operation Follow-up and control of the grid state. Planning the operation procedures of the grid Fault management Practical arrangements for maintenance of the grid components 104
  • Monitoring the grid High voltage and middle voltage network is highly automated. The low voltage network is not. The only way the operator gets the information of the fault, is usually customer report.  The situation is changing, thanks to AMR systems. 105
  • High voltage, middle voltage, low voltage In terms of electric safety:  High voltage = HV: > 1000 VAC, > 1500 VDC  Low voltage = LV: > 50 VAC, > 120 VDC  Extra low voltage: ELV: < 50 VAC, < 120 VDC In terms of electricity distribution:  Middle voltage: 1…45 kV 106
  • SCADA Supervisory Control and Data Acquisition:  Logging the events  Control of the state of the switches in grid.  Remote control  Distant reading  Reporting SCADA = high reliability information system for operating the grid 107
  • Communications Radio link Optical fiber (sometimes with 110 kV shield wires). DLC (Distribution Line Carrier):  20 kV, 3-5 kHz carrier. Will pass the distribution transformers.  Typical application: day/night tariff control.  In low-voltage network, a carrier of 150-200 kHz is used. 108
  • Power quality (SFS-EN 50160) Frequency (+/- 1 %) Voltage (+10 %, - 15 %) Fast transients Voltage dips Transient overvoltage (1,5 kV, 6 kV) Short blackouts (< 3 min) Long blackouts Harmonics 109