1. ET3480 Power Systems David Morrisson MS,MBA Week 1

2. Analyze the overall function of a typical residential and commercial electrical power distribution system.
Unit Learning Outcomes
List the basic elements of an electrical power distribution system.
List the apparatus and safety devices in a typical residential or commercial power riser diagram.
Label the various phase and line voltages in a typical three-phase electrical service diagram.
Explain the significance of the National Electrical Code (NEC) in establishing standards for design, safe installation, and maintenance of electrical wiring, apparatus, and equipment.
Calculate the NEC minimum demand loads for a residential or commercial occupancy using load diversity.
Determine the monthly power bill using the peak power demand, power usage, and power rate schedule.

3. Key Concepts Electrical components, apparatus, and safety devices
Riser diagrams (residential/commercial)
Three-phase electrical service diagrams
Electrical planning (load demand), design documents, and installation
Power bill

4. The Power Grid From Generation to the Home

5. The Basics
Every power grid in the U.S. has a few essential components.
These components include the following:
A source: the power plant
A transmission system
A hub: the substation
A distribution system
A user: the home or business

6. The Source: The Power Plant
Essentially, there are only a few ways to generate AC electricity.
For the vast majority of electricity in the U.S. a fuel (coal, natural gas, a nuclear reaction) is used to create electricity.
In addition, solar, wind and hydroelectric methods are used to generate electricity.

7. The Heart: The Steam Turbine
Once a fuel has created sufficient heat, steam is created.
Pressure from the steam is used to rotate the steam turbine.
The turbine has magnets attached to the end.
These magnets rotate within coils, thus generating an AC signal.

8. Electrical Generation: Coal, Natural Gas, & Diesel

9. Nuclear Generation

10. Transmission and Distribution
Once produced, electricity must be distributed.
The main device used to achieve this is the transformer.
Transformers convert AC voltages.
Step-up transformers convert from low to high voltages.
Step-down transformers convert from high to low voltages.

11. Transmission and Distribution
Power plant transformers step up voltages to reach substations and are sent at approximately 550kV.
Once at the substation, transformers are used to step down voltages to approximately 13kV.
These 13kV voltages are sent via distribution lines to your neighborhood home or business.
Once in the neighborhood, transformers are used (on poles or set on the ground) to step down the electrical voltage to 120/240.

12. Transmission and Distribution
From the power plant, via transmission lines to the substation.
From the substation, via distribution lines to the home.
All through the use of the transformer.

13. The Entire System

14. The Source: The Power Plant
Essentially, there are only a few ways to generate AC electricity.
For the vast majority of electricity in the U.S. a fuel (coal, natural gas, a nuclear reaction) is used to create electricity.
In addition, solar, wind and hydroelectric methods are used to generate electricity.

15. The Heart: The Steam Turbine
Once a fuel has created sufficient heat, steam is created.
Pressure from the steam is used to rotate the steam turbine.
The turbine has magnets attached to the end.
These magnets rotate within coils, thus generating an AC signal.

16. Electrical Generation: Coal, Natural Gas, & Diesel

17. Relevant Links http://www.earthlyissues.c om/nuclearplants.htm
any.com/learningpower/po werinfo_5.aspx
All links checked 07/11/12

18. Nuclear Generation

19. ELECTRICAL COMPONENTS
SMALL COMPONENTS

20. Circuit Protection

21. Types of Fused Protection
Circuit Protection
Types of Fused Protection
How to
pull them

22. Auto-fuse (blade type and Color coded)
Fuses
Auto-fuse (blade type and Color coded)
Mini-fuse
Maxi-fuse
A. TEST HOLES
B. REMOVAL

23. Maxi-fuses Combination blade / cartridge Protects main circuits
Safer than fusible link
Cover fewer circuits than a fusible link
Often in Power Distribution box

24. Ceramic and Glass Rated by current failure level
Three letter code for type and size
Glass style replaces ceramic
Caution in pulling

25. Two reasons for blowing
Where do they blow?
Why?

26. ? New Circuits What size of fuse should I install?
Use Watts law. Watts divided by volts

27. FUSIBLE LINKS Lighter gauge wire than main conductor
Covered with special insulation
Protect Main circuits
Usually under hood

28. Fusible Links Repair Visual checks
Location
Circuits protected
Insulation
Visual checks
Installing a new link
4 wire sizes smaller (4 numbers larger)
Soldering

29. Fuses
Male Pal fuses
Female Pal fuses
Bolt on Pal Fuses

30. Circuit Breaker
Why circuit breakers
Styles
Deterioration

31. TESTING CIRCUIT PROTECTION DEVICES
Must inspect closely
Type of failure determines cause
Best to use DVOM
Do not overload circuit by installing to large of fuse or tin foil
Connections must be tight
Do not use un-fused jumper wire

32. Electrical Components

33. Switches Controls electrical current (N.O. or N.C.)
Single-pole, single throw (SPST)
Momentary Switch
Single-pole, double throw switch (SPDT)
Ganged Switch

34. Relays Electromagnetic Switches (Relays) Two Circuits Control Circuit
Load Circuit
Magnetic field operates contacts
Late model relays are universal

35. TESTING RELAYS Can use several methods to test
Must Check both circuits
Be careful using test light if relay is operated by computer
Can bench test if needed
Some relays have schematic on them
Must be correct resistance

36. SOLENOIDS Electromagnetic device with a iron core Does mechanical work
Core is moveable and does work
Can test with DVOM

37. STEPPED RESISTORS Usually used to control fan motor speeds
Resistance is changed by control of switch
Controls current to change speeds
Thermal fuse

38. Variable Resistors Rheostats Potentiometer
Two terminals
Higher current
Potentiometer
Three terminals
Lower current
Many uses for variable types

39. The three types of circuit defects are:
Shorts
Grounds
Opens
poor connections

40. TESTING FOR CIRCUIT DEFECTS
DVOM IS BEST TO USE!
Must know circuit operation before can diagnose problem
Must know how to use equipment and which equipment to use.

41. See the file: Industrial Electrical

43. Three-Phase Advantages
Three-Phase Circuits
Three-Phase Advantages
The horsepower rating of three-phase motors and the kVA rating of three-phase transformers are 150% greater than single-phase motors or transformers of similar frame size.
The power delivered by a single-phase system pulsates and falls to zero. The three-phase power never falls to zero. The power delivered to the load in a three-phase system is the same at any instant. This produces superior operating characteristics for three-phase motors.
A three-phase system needs three conductors; however, each conductor is only 75% the size of the equivalent kVA rated single-phase conductors.

44. Three-phase power never falls to zero.
Three-Phase Circuits
27-2
Three-phase power never falls to zero.

45. Three-phase voltages with 120 degrees
Three-Phase Circuits
27-4
Three-phase voltages with 120 degrees
of phase shift.

46. Three-Phase Circuits Basic Properties
Three-phase systems have either three or four conductors.
There are three-phase conductors identified as A, B, and C.
The three phases are 120 degrees out of phase with each other (360 divided by 3).
There is sometimes a fourth conductor, which is the neutral.

47. Three-Phase Circuits Wye Connections
The wye, or star, connection is made by connecting one end of each of the phase windings together in a common node.
Each phase winding has a voltage drop known as the phase voltage.
The line voltage is measured from phase conductor to a different phase conductor.

48. Three-Phase Circuits Wye Connections
In a wye system, the line voltage is higher than the phase voltage by a factor of the square root of 3 (1.732).
ELine = EPhase x 1.732
EPhase = ELine / 1.732

49. Three-Phase Circuits Wye Connections
In a wye system, the line current is equal to the phase current.
ILine = IPhase

50. Line and phase voltages in a wye connection.
Three-Phase Circuits
27-6
Line and phase voltages in a wye connection.

51. Line and phase currents in a wye connection.
Three-Phase Circuits
27-7
Line and phase currents in a wye connection.

52. Vector sum of typical wye system voltages.
Three-Phase Circuits
27-10
Vector sum of typical wye system voltages.

53. Three-Phase Circuits Delta Connections
In a delta system, the line current is higher than the phase current by a factor of the square root of 3 (1.732).
ILine = IPhase x 1.732
IPhase = ILine / 1.732

54. Three-Phase Circuits Delta Connections
In a delta system, the line current is equal to the phase current.
ELine = EPhase

55. Delta system voltage and current relationships.
Three-Phase Circuits
27-14
Delta system voltage and current relationships.

56. Delta system division of currents.
Three-Phase Circuits
27-15
Delta system division of currents.

57. Three-Phase Circuits
Three-Phase Power
Three-phase power can be computed in two ways, using line values or phase values.
VA =  3 x ELine x ILine
VA = 3 x EPhase x IPhase
Note that this is the same on wye or delta systems.

58. Three-Phase Circuits Three-Phase Power
Computing watts requires using the power factor (PF).
P = 3 x ELine x ILine x PF
P = 3 x EPhase x IPhase x PF
Note that this is the same on wye or delta systems.

59. Three-Phase Circuits
27-18
Example #1 given values.

60. Three-Phase Circuits
27-19
Example #2 given values.

61. Three-Phase Circuits
27-20
Example #3 given values.

62. Three-Phase Circuits
27-21
Example #4 given values.

63. Three-Phase Circuits Review:
The voltages of a three-phase system are 120° out of phase with each other.
The two types of three-phase connections are wye and delta.
Wye connections are characterized by the fact that one terminal of each of the devices is connected together.

64. Three-Phase Circuits Review:
In a wye connection, the phase voltage is less than the line voltage by a factor of The phase current and the line current are the same.
In a delta connection, the phase voltage is the same as the line voltage. The phase current is less than the line current by a factor of