1. ECE 333 Renewable Energy Systems Lecture 5: Transformers, Harmonics, Power Industry History Prof. Tom Overbye Dept. of Electrical and Computer Engineering University of Illinois at Urbana-Champaign overbye@illinois.edu

2. Announcements Be reading Chapter 3 from the book Homework 2 is 2.16, 3.5, 3.8, 3.12, 3.13 It will be covered by an in-class quiz on Thursday Feb 5 Talk by Jana Sebestik, "Sparking Interest in Smart Grid Stuff", Friday Feb 6 at 1pm in NCSA Auditorium 1

3. Internships: San Diego Gas & Electric 2

4. In the News In a report released on Jan 29, 2015, the World Resources Institute released a report stating that Western governments made a mistake supporting large-scale conversion of plants into fuel Key point is biofuels are so inefficient they are unlikely to ever supply a substantial portion of global energy demand – Biofuel claims have been vastly exaggerated – Inherent competition between using plants and land for biofuels versus their use for food and carbon storage; 30 to 40% of US corn crop is currently converted to fuel 3 Source: NYTimes, "New Report Urges Western Governments to Reconsider Reliance on Biofuels," Jan 28, 2015

5. US Corn Prices, Last Five Years 4 http://spendmatters.com/wp/wp-content/uploads/2014/05/Corn-CBOT.jpg (CBOT is Chicago Board of Trade)

6. Transformers Overview Power systems are characterized by many different voltage levels, ranging from 765 kV down to 240/120 volts. Transformers are used to transfer power between different voltage levels. The ability to inexpensively change voltage levels is a key advantage of ac systems over dc systems. In 333 we just introduce the ideal transformer, with more details covered in 330 and 476. 5

7. Distribution Transformer Picture 115 – 35 kV distribution transformer Radiators W/Fans LTC 6

8. Transmission Level Transformer 230 kV surge arrestors 115 kV surge arrestors Oil Cooler Radiators W/Fans Oil pump 7

9. Ideal Transformer We’ll develop the voltage/current relationships for an ideal transformer – no real power losses – magnetic core has infinite permeability – no leakage flux We’ll define the “primary” side of the transformer as the side that usually takes power, and the secondary as the side that usually delivers power. – primary is usually the side with the higher voltage, but may be the low voltage side on a generator step-up transformer. 8

10. Ideal Transformer Relationships 9

11. Current Relationships 10

12. Current/Voltage Relationships 11

13. Impedance Transformation Example Example: Calculate the primary voltage and current for an impedance load on the secondary 12

14. Real Transformers Real transformers – have losses – have leakage flux – have finite permeability of magnetic core Also issues about how three phase transformers are connected Details are covered in ECE 330 and 476 13

15. Residential Distribution Transformers Single phase transformers are commonly used in residential distribution systems. Most distribution systems are 4 wire, with a multi-grounded, common neutral. 14

16. Power System Harmonics So far class has talked about fundamental frequency analysis. Many traditional loads only consume power at the fundamental frequency. However, some loads, mostly electronic-based, tend to draw current in non-linear pulses, which gives rise to harmonics. – If current has half-wave-symmetry (values are equal and opposite when separated by T/2) then there are no even harmonics 15

17. Quick Review of Fourier Analysis. 16

18. Quick Review of Fourier Analysis. 17

19. Switched-Mode Power Supply Current Source: www.utterpower.com/commercial_grid.htm 18

20. Harmonic Current Spectrum The below figure shows the harmonic current components for an 18-W, electronic-ballast compact fluorescent lamp. Source: Fig 2.34 of “Renewable and Efficient Electric Power Systems” by Masters, 1st edition 19

21. Current Waveform for CFL Figure 2.35 20

22. Total Harmonic Distortion (THD) 21

23. Key Problems with Harmonics A key problem with the third harmonic is neutral current since the fundamental 120 degree phase shift becomes 360 degrees for the third harmonic so the third harmonic values do not cancel (also true for other triplen harmonics) – Delta-grounded wye transformers prevent triplen harmonic currents from flowing into the power grid Harmonics cause transformer overheating since core losses are proportional to frequency Harmonic resonance, particularly with shunt capacitors (can be around 5 th or 7 th harmonic values) 22

24. Power Supplies for AC to DC Two main types of power supplies: linear (simpler) and switched-mode (more efficient) Linear Switched-mode 23

25. A Little Background on the Electric Utility Industry First real practical uses of electricity began with the telegraph (around the civil war) and then arc lighting in the 1870’s (Broadway, the “Great White Way”). Central stations for lighting began with Edison in 1882, using a dc system (safety was key), but transitioned to ac within several years. Chicago World’s fair in 1893 was key demonstration of electricity High voltage ac started being used in the 1890’s with the Niagara power plant transferring electricity to Buffalo; also 30kV line in Germany Frequency standardized in the 1930’s 24

26. Regulation and Large Utilities Electric usage spread rapidly, particularly in urban areas. Samuel Insull (originally Edison’s secretary, but later from Chicago) played a major role in the development of large electric utilities and their holding companies – Insull was also instrumental in start of state regulation in 1890’s Public Utilities Holding Company Act (PUHCA) of 1935 essentially broke up inter-state holding companies – This gave rise to electric utilities that only operated in one state – PUHCA was repealed in 2005 For most of the last century electric utilities operated as vertical monopolies 25

27. Vertical Monopolies Within a particular geographic market, the electric utility had an exclusive franchise Generation Transmission Distribution Customer Service In return for this exclusive franchise, the utility had the obligation to serve all existing and future customers at rates determined jointly by utility and regulators It was a “cost plus” business 26

28. Vertical Monopolies Within its service territory each utility was the only game in town Neighboring utilities functioned more as colleagues than competitors Utilities gradually interconnected their systems so by 1970 transmission lines crisscrossed North America, with voltages up to 765 kV Economies of scale keep resulted in decreasing rates, so most every one was happy 27

29. History, cont’d -- 1970’s 1970’s brought inflation, increased fossil-fuel prices, calls for conservation and growing environmental concerns Increasing rates replaced decreasing ones As a result, U.S. Congress passed Public Utilities Regulator Policies Act (PURPA) in 1978, which mandated utilities must purchase power from independent generators located in their service territory (modified 2005) PURPA introduced some competition, but its implementation varied greatly by state 28

30. PURPA and Renewables PURPA, through favorable contracts, caused the growth of a large amount of renewable energy in the 1980’s (about 12,000 MW of wind, geothermal, small scale hydro, biomass, and solar thermal) – These were known as “qualifying facilities” (QFs) – California added about 6000 MW of QF capacity during the 1980’s, including 1600 MW of wind, 2700 MW of geothermal, and 1200 MW of biomass – By the 1990’s the ten-year QFs contracts written at rates of $60/MWh in 1980’s, and they were no longer profitable at the $30/MWh 1990 values so many sites were retired or abandoned 29

31. Abandoned Wind Farm Need South Point in Hawaii Source: Prof. Sanders 30

32. Electricity Prices, 1960-2010 Source: EIA, Annual Energy Review, 2010, Figure 8.10 31

33. History, cont’d – 1990’s & 2000’s Major opening of industry to competition occurred as a result of National Energy Policy Act of 1992 This act mandated that utilities provide “nondiscriminatory” access to the high voltage transmission Goal was to set up true competition in generation Result over the last few years has been a dramatic restructuring of electric utility industry (for better or worse!) Energy Bill 2005 repealed PUHCA; modified PURPA 32

34. Historic State Variation in Electric Rates 33

35. The Goal: Customer Choice 34

36. The Result for California in 2000/1 OFF 35

37. The California-Enron Effect Source : http://www.eia.doe.gov/cneaf/electricity/chg_str/regmap.html RI AK electricity restructuring delayed restructuring no activity suspended restructuring WA OR NV CA ID MT WY UT AZ CO NM TX OK KS NE SD ND MN IA WI MO IL IN OH KY TN MS LA AL GA FL SC NC W VA PA NY VT ME MI NH MA CT NJ DE MD AR HI DC 36

38. August 14 th, 2003 Blackout 37

39. My Favorite 8/14/2003 Blackout Cartoon! 38