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

1. Production and Distribution of
Electricity
http://www.flickr.com/photos/31119160@N06/8007585111/
Vesa Linja-aho — Spring 2013

2. 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

3. 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

4. We start with prerequisite exam
4

5. 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

6. It is fairly easy to distribute electricity
with 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

7. Homework
 Read the following article:
 http://en.wikipedia.org/wiki/War_of_Currents
 We will discuss it on Monday
7

8. Homework
 Read the following article:
 http://en.wikipedia.org/wiki/War_of_Currents
 We will discuss it on Monday
8

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. The pricing
 The cost of the transmission is typically 15-50
% of the total price of the electricity. (average
for consumers: 30 %).
17

18. What if I used a personal generator?
 Cost of fuel?
 Heat of Combustion?
 Cost of equipment?
 Efficiency?
18

19. Environmental aspects in distribution and
transmission of electricity
 Landscape protection
 Wood preservation agents
 Transformer oil leaks
 SF 6 in circuit breakers
 Noise
19

20. 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

21. 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

22. 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

23. 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

24. 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

25. Recycling of equipment
 Wires
 Poles
 Transformers
25

26. Noise
 50 Hz / 60 Hz hum
 High voltage switchgear
26

27. 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

28. How to increase efficiency?
 Raise the voltage
 Use an extra 1 kV step in distibution (for
distances of couple of kilometers).
28

29. Environmental aspects of Electricity
Production
 Heat
 CO 2
 Particles
 Accidents
 Water usage
 Nuclear waste
 Mining and refining
 Loss of land
 …
29

30. Most significant sources in the world
 Coal 41 %
 Natural Gas 21 %
 Hydroelectric 16 %
 Nuclear 13 %
 Oil 5 %
 Other 3 %
30

31. Renewable
 Hydroelectric 92 %
 Wind 6 %
 Geothermal 1,8 %
 Solar photovoltaic 0,06 %
 Solar thermal 0,004 %
31

32. 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

33. Environmental aspects of Electricity
Production
 Heat
 CO 2
 Particles
 Accidents
 Water usage
 Nuclear waste
 Mining and refining
 Loss of land
 …
33

34. Most significant sources in the world
 Coal 41 %
 Natural Gas 21 %
 Hydroelectric 16 %
 Nuclear 13 %
 Oil 5 %
 Other 3 %
34

35. Renewable
 Hydroelectric 92 %
 Wind 6 %
 Geothermal 1,8 %
 Solar photovoltaic 0,06 %
 Solar thermal 0,004 %
35

36. 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

37. 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

38. Fossil fuel power generation
 Basic idea: burn something, generate steam for
turbine.
 Efficiency: 33-48 %
38

39. Cogeneration, CHP combined heat&power
 Efficiency: over 80 %.
39

40. Combined cycle power plant
 Gas turbine + steam turbine.
 Efficiency over 60 % (even 90 % with CHP)
40

41. 41

42. Hydroelectric power plant
 Water rotates a turbine
 Efficiency little over 90 %
42

43. Nuclear power
 PWR (Pressurized water reactor)
 BWR (Boiling water reactor)
 Efficiency: about > 30 %
43

44. Pressurized water reactor PWR
44

45. Boiling water reactor (BWR)
45

46. 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

47. Elements of the transmission and
distribution system
 Substations
 Transformers
 Protective equipment
 Transmission and distribution lines
47

48. 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

49. 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. 50

51. 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

52. 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

53. 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

54. 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

55. Three classes of electric qualification
 EQ 1 (general).
 EQ 2 (low-voltage).
 EQ 3 (low-voltage repair).
55

56. Electric deaths in Finland (moving average)
non-professionals
professionals
56

57. 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

58. 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

59. Electric network in buildings
 Small buildings: 400 V / 230 V
 Larger buildings: own 20 kV transformer
 Industry: 110 kV input
59

60. 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

61. 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

62. Class I plug + socket
62

63. Protection systems
 Basic insulation (Class 0)
 Protect earth (Schuko) (Class I)
 Double insulation (Class II)
63

64. 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

65. 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

66. 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

67. 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

68. Distributed production of electricity
 Centralized vs. distributed?
68

69. Benefits of centralized production
 Economics of scale
 Higher efficiency
 Low-loss transmission
 Reliability
 Environment (plants away from cities)
69

70. 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

71. Distributed generation in EU (2004)
71

72. Less pollution
 ”Free” fuel (hydroelectric, wind)
 Production near the end user  less
transmission losses.
 Easier cogeneration
72

73. Economic benefits
 Lower threshold for entering the market
 Modularity and easy expandability
 Faster construction
 Lower capital costs
73

74. Support from the state
 Subvention for production
 Tax relief
 Product development aid
 Obligation for network company to buy the
electricity in fixed price.
74

75. Examples
 Small wind farm
 Small CHP for greenhouses
 Fuel cell, solar, combustion engine or
microturbine plant
75

76. 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

77. Group work
 Article: Rural Electrification in Developing
Countries. From book Lakervi, Partanen:
Sähkönjakelutekniikka. 3. ed. 2008. Otatieto.
Pp. 286—295.
77

78. Rural electrification (in developing
countries)
 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

79. Rural electrification in developing
countries
 About 4 billion people have access to
electricity (of 7 billion people).
 Social impact.
 Economic impact.
 Environmental impact.
79

80. Conditions vary considerably
 Some relatively poor countries have high
percentage in rural electrification (Costa Rica,
Tunisia).
80

81. 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

82. Solutions
 Hydroelectric power, if available, is the best
solution (almost zero maintenance).
 Diesel unit a popular choice.
82

83. 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

84. Challenges
 The wealthy demand high reliability and
voltage stability.
 The poor demand low tariffs and fast
progression of electrification.
84

85. 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

86. History
 Electricity metering
 Dual tariff system
86

87. 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

88. 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

89. Reliability
 Automatic fault detection and healing.
89

90. 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

91. Flexibility
 Traditional network protection gear is designed
for one-way power flow.
91

92. Sustainability
 Large amounts of renewable energy need
sophisticated network automation.
 For example, solar power output changes
suddenly.
92

93. 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

94. 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

95. Asset management in electricity
distribution
 Grid development
 Grid maintenance
 Grid operation
95

96. Grid development process
 Based on the network strategy (environment,
basic principles, present state, main measures
for development)
96

97. 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

98. 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

99. Grid maintenance
 Fixing maintenance
 Preventive maintenace
 TBM = time based maintenance
 CBM = condition based maintenance
 RBM = reliability based maintenance
99

100. Reliability based maintenance
c repair
o
n
overhaul
d
i
t test
i Service if
o necessary
n
significance
100

101. 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

102. Examples of routine maintenance
 Clearance of the right-of-way of the power
lines.
 Monitoring the oil temp of transformers
 Thermal imaging
102

103. 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

104. 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

105. 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

106. 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

107. 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

108. 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

109. 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