Power Transmission lines

Diego Flores

EE4347 Applied electromagnetics

December 10, 2014

Dr. Raymond C. Rumpf

Summery I will be talking about transmission lines; what are they, what they do and some components that are important to know. I will also be talking about some problems that underground transmission lines have and the reason why we don’t use them as much as an overhead transmission line. I will also be comparting transmission line with under ground transmission lines.

Types of power transmission lines

• Transmission Nominal Voltage: +/- 400 kV HVDC

Type: Tower Typical Tower Height: 145-180 feet Typical Right-of-Way Width: 160-180 feet

• Transmission Nominal Voltage:500 kV Type: Tower Typical Tower Height: 90-150 feet Typical Right-of-Way Width: 160-200 feet

• Transmission Nominal Voltage:345 kV Type: Double Ckt Pole Typical Tower Height: 115-150 feet Typical Right-of-Way Width: 140-160 feet

• Transmission Nominal Voltage:230 kV Type: H-Frame Typical Tower Height: 60-90 feet Typical Right-of-Way Width: 100-160 feet

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Transmission Nominal Voltage: 161 kV Type: Single Pole Typical Tower Height: 70-95 feet Typical Right-of-Way Width: 100-150 feet

Transmission Nominal Voltage:115 kV Type: Single Pole Typical Tower Height: 55-80 feet Typical Right-of-Way Width: 90-130 feet

Transmission Nominal Voltage: 69 kV Type: Single Pole Typical Tower Height: 50-70 feet Typical Right-of-Way Width: 70-100 feet

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What is power transmission line A transmission line is the bulk transfer of electrical energy, from generating power plant to electrical substations located near demand centers.

How electricity is deliver

• Transformers at the generator plats increase the voltage up to 69kv, 115kv,230kv, 500kv,765kv .

• Transformers reduction [2]

Transmission substation (69 kv,34kv)[2]

Local distribution substation (69 kv,34kv)[2]

• Large industrial user (2400 to 2400 volts ) [2]

• Distribution lines (120/240) or (120/208 volts)[2]

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Components of the transmission line system

• 3 wires

• A shield wire

• Spacers

• Insulators

3 wires on a transmission line

• The 3 wires that the transmission line has are call conductor.

• The electricity is transmitted at high voltages to reduce the energy lost in long distance transmission.

shield wire

• Shield wires are use to protect the tower from lighting.

• They can sometimes contain fiber optics communication cables.

Spacers

• Spacers are designed to keep the individual wires in a bundle separated by a fixed distance, usually 18 inches.

Insulators

• Transmission line insulators are devices used to contain, separate or support electrical conductors on high voltage electricity supply networks.

Problems with Underground transmission lines

Transfer high voltage

Cost Four to fifteen times the cost

Repairs

Line length challenges

Network

Life expectancy

EMF of transmission lines

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Fields surrounding wires

• Electric fields are weakened by materials ,therefor, it is not dangerous.

• One problem with magnetic fields is that they can pass through most materials, therefor, people are expose to small magnetic fields and that can cause health problems such as skin cancer, brain cancer, breast cancer, leukemia.

Future of transmission lines

• Smart Grid

– It’s a better way to communicate with the utility, and the costumer.

– It will be quicker to restore electricity after power disturbance.

– It will be a better way to save money because there will be a better control over the electricity been use.

References

• [1] http://www.classroom-energy.org/energy_09/new-window/4_electric_transmission.html

• [2] http://www.minnelectrans.com/transmission-system.html • [3]http://www.emfs.info/sources/overhead/ • [4] http://www.electrical4u.com/electrical-power-transmission-

system-and-network/ • [5]http://psc.wi.gov/thelibrary/publications/electric/electric09.pdf • [6]http://emlab.utep.edu/pdfs/Summary%20of%20Transmission%

20Lines.pdf • [7]https://www.smartgrid.gov/the_smart_grid • [8] http://www.niehs.nih.gov/health/topics/agents/emf/