0-electrical Intro
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ELECTRIC CIRCUITS THEORY
These lecture slides have been compiled by Mohammed SalahUdDin Ayubi. LECTURE 0
Electrical Technology Introduction 05 August 2005
Engineer M S Ayubi
1
ELECTRIC CIRCUIT IS AN INTERCONNECTION OF ELECTRICAL COMPONENTS
L R1 R2 vS
+ vO −
+ -
C TYPICAL LINEAR IRCUIT 05 August 2005
Engineer M S Ayubi
2
EE Subdisciplines • • • • • •
Power Electromagnetics Communication/Signal Processing Digital Controls Solid State
05 August 2005
Engineer M S Ayubi
3
Power • • • •
Generation of electrical energy Storage of electrical energy Distribution of electrical energy Rotating machinery-generators, motors
05 August 2005
Engineer M S Ayubi
4
Electromagnetics • • • •
Propagation of electromagnetic energy Antennas Very high frequency signals ~ 108 Hz Fiber optics ~ 1G b/s
05 August 2005
Engineer M S Ayubi
5
Communications/Signal Proc. • Transmission of information electrically and optically • Modification of signals – enhancement – compression – noise reduction – filtering 05 August 2005
Engineer M S Ayubi
6
Digital • Digital (ones and zeros) signals and hardware • Computer architectures • Embedded computer systems – Microprocessors – Microcontrollers – DSP chips 05 August 2005
Engineer M S Ayubi
7
Controls • Changing system inputs to obtain desired outputs • Feedback • Stability
05 August 2005
Engineer M S Ayubi
8
Solid State • Devices – Transistors – Diodes (LED’s, Laser diodes) – Photodetectors • Miniaturization of electrical devices • Integration of many devices on a single chip (VLSI) 05 August 2005
Engineer M S Ayubi
9
Electric Power
05 August 2005
Engineer M S Ayubi
10
The Electrical Power System • Power is one of the main subdisciplines of EE. • The power generation, transmission and distribution system is something we all use all the time. • It is an excellent example of a case where electrical networks are used to model the flow of energy. 05 August 2005
Engineer M S Ayubi
11
Consider what we do here. • We usually generate a huge amount of power in a centralized location. • We ship it to you when you flip the switch • You then decide that you will light a desk lamp located 18 inches above your desk, about 2 feet in on the right. • You can easily change your mind and put the lamp on the left! • This is magic.
05 August 2005
Engineer M S Ayubi
12
Electric Load •
•
•
•
The load changes continuously – Daily – Seasonal The daily maximum occurs around 4-6 PM , the minimum at night. The load or demand is defined as the average load (MW) for 15 minutes Seasonal changes: Summer load is higher than the winter load in AZ.
• • •
Base load (large thermal and nuclear plants) Intermediate loads (medium steam and hydro) Peak load (gas turbine and combined cycle plants)
Typical Daily Load Curve P_max
Peak load Intermediate load Base load 0
05 August 2005
Engineer M S Ayubi
6
12
18
24 13
What to notice about what follows • We do NOT create energy out of nowhere. • Instead, we convert some form of energy. In a fossil power plant, chemical energy is converted to a mechanical motion of a rotating turbine and generator. The result is electric energy.
05 August 2005
Engineer M S Ayubi
14
Electrical Power Transmission 1) The generating station converts the energy of gas, oil, coal or nuclear fuel to electric energy. The generator voltage is around 15-25 kV
2) The main transformer increases the voltage to 230-765 kV. This reduces the current and losses. 3) The high voltage transmission line transports the energy from the generating station to the large loads, like towns. Example: Energy generated at Palo Verde is transported by 500 kV lines to Phoenix, San Diego, Los Angeles, Albuquerque and El Paso.
05 August 2005
Engineer M S Ayubi
15
Electrical Power Transmission 4) The high voltage substation reduces the voltage to 120-69 kV. The substation serves as a node point for several lines. 5) The sub-transmission lines (69 kV-120 kV) connect the high voltage substation with the local distribution station. 6) Distribution lines (12 -15 kV) distribute the energy along streets or underground. Each line supplies several step down transformers distributed along the line. 7) The distribution transformer reduces the voltage to 230/115V, which supplies the houses, shopping centers etc..
05 August 2005
Engineer M S Ayubi
16
Generating Station Type of Generation stations • Thermal Power Plant. The large (more than 500 MVA) plants carry constant load (base load plant), Smaller plants loads are regulated but they operate continuously. Minimum down time is 20-35 hours. •
Nuclear Power Plant. These plants carry constant load and are used as base loads plants.
•
Hydroelectric Plants. It is economically desirable to load these plants to the maximum capacity, because of the low energy cost. (Water is free). Other factors: flood control, irrigation and salmon migration.
•
Combined steam and Gas-Turbine Power Plants. High efficiency plants for variable load.
•
Gas-turbine. Peak load plants, high operating and low investment cost
• Solar, Wind. Loaded to the maximum capacity, when sun or wind power available.
05 August 2005
Engineer M S Ayubi
17
Hydro Power Plant • The water is stored in the lake, which is at higher ground (Lake Pleasant). • A canal and pipe system transfers the water to the power house. • The potential energy of the water is transformed to mechanical energy in the turbine. • The turbine drives the generator and converts the water mechanical energy to electrical energy.
05 August 2005
Engineer M S Ayubi
18
Motion to Electricity
When magnets are moved near a wire, an electric current is generated in that wire.
05 August 2005
Engineer M S Ayubi
19
Generating Station
05 August 2005
Engineer M S Ayubi
20
Transmission Lines Type of transmission lines: •
•
Extra high voltage lines – 345 kV, 500 kV, 785 kV – Interconnection between systems. (National Grid) High Voltage lines – 120 kV, 220 kV – Inter connection between substations.
05 August 2005
•
•
•
Sub-transmission lines – 45 kV, 69 kV, 120 kV – Substation and large customer Distribution Line – 2.4 kV- 45 kV , 15 kV – Supplies houses High Voltage DC lines – 120 kV- 600 kV – Interconnection between regions. (Oregon-California)
Engineer M S Ayubi
21
AC versus DC • AC is alternating current • AC quantities always vary sinusoidally in time • Usually, we will know the frequency and solve for the amplitude and phase. 05 August 2005
• DC is direct current • DC quantities are always constant in time. • DC can not be directly transformed to lower or higher voltages.
Engineer M S Ayubi
22
Why do we use AC for power transmission? • Power levels correspond to V2. Therefore, to get a huge power out of Palo Verde, we need huge V’s. We need to step the voltage down before it reaches our classroom. The power company wants to do this in a lossless fashion. AC allows them to do this by using transformers.
05 August 2005
Engineer M S Ayubi
23
Why Are There Three Conductors in Power Transmissions Lines? • Most AC power transmission systems have three conductors. • The voltage on each phase (referenced with respect to earth ground) is a sinusoid with a phase difference of 120° from the voltages in the other two phases.
05 August 2005
Engineer M S Ayubi
24
Three Phase • A three conductor transmission system is called a three-phase system. • The power delivered by a three phase system (assuming a balanced load) is constant, even though the voltages in each phase vary sinusoidally. • Three phase systems are more efficient than single systems due to reduced power losses.
05 August 2005
Engineer M S Ayubi
25
These lecture slides have been compiled by Mohammed SalahUdDin Ayubi. LECTURE 0
Electrical Technology Introduction 05 August 2005
Engineer M S Ayubi
1
ELECTRIC CIRCUIT IS AN INTERCONNECTION OF ELECTRICAL COMPONENTS
L R1 R2 vS
+ vO −
+ -
C TYPICAL LINEAR IRCUIT 05 August 2005
Engineer M S Ayubi
2
EE Subdisciplines • • • • • •
Power Electromagnetics Communication/Signal Processing Digital Controls Solid State
05 August 2005
Engineer M S Ayubi
3
Power • • • •
Generation of electrical energy Storage of electrical energy Distribution of electrical energy Rotating machinery-generators, motors
05 August 2005
Engineer M S Ayubi
4
Electromagnetics • • • •
Propagation of electromagnetic energy Antennas Very high frequency signals ~ 108 Hz Fiber optics ~ 1G b/s
05 August 2005
Engineer M S Ayubi
5
Communications/Signal Proc. • Transmission of information electrically and optically • Modification of signals – enhancement – compression – noise reduction – filtering 05 August 2005
Engineer M S Ayubi
6
Digital • Digital (ones and zeros) signals and hardware • Computer architectures • Embedded computer systems – Microprocessors – Microcontrollers – DSP chips 05 August 2005
Engineer M S Ayubi
7
Controls • Changing system inputs to obtain desired outputs • Feedback • Stability
05 August 2005
Engineer M S Ayubi
8
Solid State • Devices – Transistors – Diodes (LED’s, Laser diodes) – Photodetectors • Miniaturization of electrical devices • Integration of many devices on a single chip (VLSI) 05 August 2005
Engineer M S Ayubi
9
Electric Power
05 August 2005
Engineer M S Ayubi
10
The Electrical Power System • Power is one of the main subdisciplines of EE. • The power generation, transmission and distribution system is something we all use all the time. • It is an excellent example of a case where electrical networks are used to model the flow of energy. 05 August 2005
Engineer M S Ayubi
11
Consider what we do here. • We usually generate a huge amount of power in a centralized location. • We ship it to you when you flip the switch • You then decide that you will light a desk lamp located 18 inches above your desk, about 2 feet in on the right. • You can easily change your mind and put the lamp on the left! • This is magic.
05 August 2005
Engineer M S Ayubi
12
Electric Load •
•
•
•
The load changes continuously – Daily – Seasonal The daily maximum occurs around 4-6 PM , the minimum at night. The load or demand is defined as the average load (MW) for 15 minutes Seasonal changes: Summer load is higher than the winter load in AZ.
• • •
Base load (large thermal and nuclear plants) Intermediate loads (medium steam and hydro) Peak load (gas turbine and combined cycle plants)
Typical Daily Load Curve P_max
Peak load Intermediate load Base load 0
05 August 2005
Engineer M S Ayubi
6
12
18
24 13
What to notice about what follows • We do NOT create energy out of nowhere. • Instead, we convert some form of energy. In a fossil power plant, chemical energy is converted to a mechanical motion of a rotating turbine and generator. The result is electric energy.
05 August 2005
Engineer M S Ayubi
14
Electrical Power Transmission 1) The generating station converts the energy of gas, oil, coal or nuclear fuel to electric energy. The generator voltage is around 15-25 kV
2) The main transformer increases the voltage to 230-765 kV. This reduces the current and losses. 3) The high voltage transmission line transports the energy from the generating station to the large loads, like towns. Example: Energy generated at Palo Verde is transported by 500 kV lines to Phoenix, San Diego, Los Angeles, Albuquerque and El Paso.
05 August 2005
Engineer M S Ayubi
15
Electrical Power Transmission 4) The high voltage substation reduces the voltage to 120-69 kV. The substation serves as a node point for several lines. 5) The sub-transmission lines (69 kV-120 kV) connect the high voltage substation with the local distribution station. 6) Distribution lines (12 -15 kV) distribute the energy along streets or underground. Each line supplies several step down transformers distributed along the line. 7) The distribution transformer reduces the voltage to 230/115V, which supplies the houses, shopping centers etc..
05 August 2005
Engineer M S Ayubi
16
Generating Station Type of Generation stations • Thermal Power Plant. The large (more than 500 MVA) plants carry constant load (base load plant), Smaller plants loads are regulated but they operate continuously. Minimum down time is 20-35 hours. •
Nuclear Power Plant. These plants carry constant load and are used as base loads plants.
•
Hydroelectric Plants. It is economically desirable to load these plants to the maximum capacity, because of the low energy cost. (Water is free). Other factors: flood control, irrigation and salmon migration.
•
Combined steam and Gas-Turbine Power Plants. High efficiency plants for variable load.
•
Gas-turbine. Peak load plants, high operating and low investment cost
• Solar, Wind. Loaded to the maximum capacity, when sun or wind power available.
05 August 2005
Engineer M S Ayubi
17
Hydro Power Plant • The water is stored in the lake, which is at higher ground (Lake Pleasant). • A canal and pipe system transfers the water to the power house. • The potential energy of the water is transformed to mechanical energy in the turbine. • The turbine drives the generator and converts the water mechanical energy to electrical energy.
05 August 2005
Engineer M S Ayubi
18
Motion to Electricity
When magnets are moved near a wire, an electric current is generated in that wire.
05 August 2005
Engineer M S Ayubi
19
Generating Station
05 August 2005
Engineer M S Ayubi
20
Transmission Lines Type of transmission lines: •
•
Extra high voltage lines – 345 kV, 500 kV, 785 kV – Interconnection between systems. (National Grid) High Voltage lines – 120 kV, 220 kV – Inter connection between substations.
05 August 2005
•
•
•
Sub-transmission lines – 45 kV, 69 kV, 120 kV – Substation and large customer Distribution Line – 2.4 kV- 45 kV , 15 kV – Supplies houses High Voltage DC lines – 120 kV- 600 kV – Interconnection between regions. (Oregon-California)
Engineer M S Ayubi
21
AC versus DC • AC is alternating current • AC quantities always vary sinusoidally in time • Usually, we will know the frequency and solve for the amplitude and phase. 05 August 2005
• DC is direct current • DC quantities are always constant in time. • DC can not be directly transformed to lower or higher voltages.
Engineer M S Ayubi
22
Why do we use AC for power transmission? • Power levels correspond to V2. Therefore, to get a huge power out of Palo Verde, we need huge V’s. We need to step the voltage down before it reaches our classroom. The power company wants to do this in a lossless fashion. AC allows them to do this by using transformers.
05 August 2005
Engineer M S Ayubi
23
Why Are There Three Conductors in Power Transmissions Lines? • Most AC power transmission systems have three conductors. • The voltage on each phase (referenced with respect to earth ground) is a sinusoid with a phase difference of 120° from the voltages in the other two phases.
05 August 2005
Engineer M S Ayubi
24
Three Phase • A three conductor transmission system is called a three-phase system. • The power delivered by a three phase system (assuming a balanced load) is constant, even though the voltages in each phase vary sinusoidally. • Three phase systems are more efficient than single systems due to reduced power losses.
05 August 2005
Engineer M S Ayubi
25
