lectric Power Transmission

7/30/2019 lectric Power Transmission

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EE2022 Electrical Energy Systems

Panida Jirutitijaroen

Department of Electrical and Computer Engineering

2/19/2013 EE2022: Electric Power Transmission by P. Jirutitijaroen 1

Lecture 11: Electric Power Transmission – Overhead Line VS Underground Cable

21/02/2013



Detailed Syllabus


31/01/2013 Three-phase power systems: Introduction to three-phase circuit. Balanced three-phase

systems. Delta-Wye connection. Relationship between phase and line quantities05/02/2013 Three-phase power systems: Per-phase analysis. Three-phase power calculation. Examples.

07/02/2013 Generation: Simple generator concept. Equivalent circuit of synchronous generators

14/02/2013 Generation: Operating consideration of synchronous generators, i.e. excitation voltage

control, real power control, and loading capability

19/02/2013 1st Mid-term test

AC circuit, power factor, power factor correction, 3-phase circuit (Tutorials 1-3)

21/02/2013 Generation: Principle of asynchronous generators. Examples.

Transmission: Overhead VS Underground cable.

05/03/2013 Transmission: Four basic parameters of transmission line.

07/03/2013 Transmission: Long transmission line model, Medium-length transmission line model, Short

transmission line model.

12/03/2013 Transmission: Operating consideration of transmission lines i.e. voltage regulation, line

loadability, efficiency. Examples.14/03/2013 Distribution: Principle of transformer. Ideal transformer. Reflected load. Impedance

matching. Practical transformer. Three-phase transformer. Examples

19/03/2013 Per unit analysis: Single-phase per unit analysis.

21/03/2013 Per unit analysis: Three-phase per unit analysis. Examples.

02/04/2013 2nd Mid-term test

Generators, transmission lines, and transformers (Tutorials 4-6)



IN THIS LECTURE

Learning outcomes

Outline

References




Learning Outcomes

• Use electrical engineering principles to explain

the basic operation of the electrical generator,

transmission line and transformer in an

electrical energy system and able to identifyand construct their equivalent circuits

appropriately.




Outline

• Overhead transmission line

• Underground cable

•

Transmission line design consideration




Reference

• Pieter Schavemaker and Lou Van Der Sluis,“Electrical Power System Essentials”.

– Chapter 3 The Transmission of Electric Energy

– Appendix E The Representation of Lines and Cables




IMPORTANCE OF TRANSMISSIONNETWORKS

Isolated grids

Advantage of Interconnected System




A Three-Phase Circuit System


3-Phase Generation

system.

3-Phase Transmission

system.

Generation (11 – 36 KV) Transmission (110 – 765 KV) Industrial customer

(23 – 138 KV)

Commercial customer

(4.16 – 34.5 KV)

Residential customer(120 – 240 V)

Generation Transmission and Distribution Load

Three-phase voltage source Three transmission lines Three-phase load



Isolated Grids


Source:

http://www.edisontechcenter.

org/HistElectPowTrans.html

- Early electric power plants are built in aremote area.

-By integrating these areas, the grid

became more stable and reliable.

-Economic operation, be able to

dispatch/use the cheap units.

-Safeguard during emergencies



Advantage of Interconnected System

• Better system efficiency – Allow different choices of energy source: wind, solar,

geothermal.

• Improve reliability –

In case some generator fail, the other can help to support thesystem.

• Smaller frequency deviation – When a load increases, an immediate reaction of a generator is

a drop in frequency because the mechanical torque can not beadjusted instantanously. With interconnection, more generatorscan share this effect which helps to alleviate the frequency drop.

• Cover large geographical area – Integration of renewable energy sources.




(Future?) Electricity Grid in Asia Pacific

• Solar power, geothermal,wind and wave energyfrom Australia.

• Geothermal power of Indonesia's volcanoes.

• Wind farm-lined in SouthChina Sea to China .

• Hydro power in Laos.

• Solar power in Thailand.

• Natural gas from Burma,Malaysia, and Indonesia.


Source: The benefits of an intercontinental

energy grid by Stewart Taggart

http://www.sciencealert.com.au/opinions/2

0092001-18696.html

“The plan would entail building a 10,000-kilometer

long electricity transmission system stretching from

Beijing to the Great Australian Bight.”



US Electric Power Grid




Singapore Electric Power Grid

• Fully underground

cable.

• 400 kV grid

• 230 kVNorthern/Southern

block

– To alleviate power

quality issue.

• 66 kV/22 kV distribution




Solar that Floats on Water


Source: http://www.youtube.com/watch?v=RIBcQe5tbxU



Types of Transmission Lines

• Overhead transmission line – Main features of overhead transmission lines

– Issues with overhead transmission lines

•

Underground cable – Types of underground cables

– Issues with underground cables

• Comparison between overhead lines and

underground cables. – Cost

– Electrical properties




OVERHEAD TRANSMISSION LINE

Main features of a transmission line

Issues with overhead transmission lines




Overhead Transmission Line

• Support structure

• Conductors

• Insulators

• Shield wires (earth

wire)


Source:

http://www.nationalgrid.com/uk/LandandDevelopment/

DDC/devnearohl_final/appendix2/



High Voltage Conductors


3M

Aluminum

Conductor

Composite

Reinforced

(ACCR)

Source:

http://www.realwire.com/release

_detail.asp?ReleaseID=13698

Source: http://www.faqs.org/sec-

filings/091214/COMPOSITE-TECHNOLOGY-

CORP_10-K/



Insulators

• Insulators are used to isolate the transmission lines fromthe tower that is connected to ground.

• Traditionally insulators are made from glass or porcelain.

• For new technology, insulators are made from composite

materials


Source: Electrical Power System

Essentials by Pieter Schavemaker

and Lou Van Der Sluis



Shield (Ground) Wires


Protected against large

lightening currents.

Small lightening currentscan still hit the tower or the

three-phase conductors.

Source: Electrical Power System Essentials



Galloping Lines


Source:

http://www.youtube.com/watch?v=ko4g

oyw1Q84&feature=related

Conductor vibration

damper

Source: Electrical Power System Essentials



Severe Weather Impact on T-Lines


Severe weather swept through west

central Minnesota on Aug. 1, 2011.

The tower was designed to withstand120 mph winds. The transmission line

operated reliably since it was energized

in 1978

2005 Hurricane Rita Damage to Gulf Transmission Lines



Environmental Impact


These pictures are taken by my friend

(P. Boonyasiriwat) in Phuket, 09/2011.

Something you don’t

see in Singapore.



UNDERGROUND CABLE

Underground cables

Types of underground cables

Issues with underground cables




Underground Cable

• The main differencebetween underground

cables and overhead

transmission line is that

for underground cable

the conductor must be

insulated from the

ground.


Source:

http://scienceservice.si.edu/pages/014005.htm

1938

G.B. Shanklin, engineer of the cable section

of the General Electric Company, points out

one of the three gas channels in a section

of gas-filled cable.



Types of Underground Cables

• Two types of cables

• Pipe-type

– All three phase conductors are contained in one pipe.

• Self-contained

– Individual phase conductor in each cable.


Pipe-Type cable Self-contained cableSource: http://electrical-engineering-portal.com/understanding-underground-electric-transmission-cables



Types of Insulation

• Three main types of insulation

• Paper-Oil insulation

– High-pressure, fluid-filled pipe (HPFF)

– Self-contained fluid-filled (SCFF)

• Paper-Gas insulation

– High-pressure, gas-filled pipe (HPGF)

• Plastic insulation

– Solid cable, cross-linked polyethylene (XLPE)




High-Voltage Underground Cable


6/10 kV cable

Source: Electrical Power

System Essentials byPieter Schavemaker and

Lou Van Der Sluis

220/380 kV cable

Self Contained

Liquid-Filled (SCLF)Cables

High Pressure Liquid-Filled Pipe-Type Cables (HPLF)

Solid cable,

cross-linked

polyethylene

(XLPE)

Liquidchannel

Source:

http://coppercanada.ca/

publications/pub21e/21

e-Section6.html



Singapore Underground Power Cables


Voltage Level 400 KV 230 kV 66 kV

Cable Type Single-core self-

contained

Single-core self-

contained

Single-core

Insulator fluid-filled

Polypropylene

Laminated Paper

(PPLP) insulated with

copper conductor

and seamless

aluminium sheath

Either fluid-filled

kraft paper insulated

or XLPE insulated

with copper

conductor and

seamless aluminium

sheath

XLPE insulated

with copper

conductor and

seamless

aluminium

sheath

Power rating 1000 MVA 500 MVA 100 MVA

Source: SP powergrid http://www.sppowergrid.com.sg/items2.htm



Underground Cable Construction


Source:

http://psc.wi.gov/thelibrary/pub

lications/electric/electric11.pdf



Issues with Underground Cables


Source: SP

Powergrid

“Working

together to

prevent cable

damage”



Underground Cable Damages


Source: SP Powergrid “Working together to prevent cable damage”



Singapore Power Cable Tunnel


Source: www.singaporepower.com.sg September 17 th 2012,

“Singapore Power today announced a S$2 billion Transmission Cable Tunnel Project to ensure that households and businesses inSingapore continue to enjoy reliable, secure and quality power supply to meet future demand. Two cross-island cable tunnels will be

constructed 60 metres underground to provide a long-term solution to the on-going upgrading and renewal of the power cable

grid infrastructure in Singapore. The deep tunnels are designed to overcome the existing congestion of underground

space and utility services in Singapore. They will facilitate faster and more efficient maintenance and replacement of cables,

thereby reducing the frequency of road-digging works and thus minimising inconvenience to the public

in the long run.”

Source: www.straitstimes.com

Singapore Power staff and the mediaon a tour inside the Labrador

Substation that is 30m underground.

-- ST PHOTO: CAROLINE CHIA

http://www.singaporepower.com.sg/

http://www.straitstimes.com/

http://www.straitstimes.com/

http://www.singaporepower.com.sg/



Electricity Cable Tunnel Project


Sewage, current power grid and natural gas

pipes: 1-3 meters deep

Underground MRT: 30 meters deep

Drainage system: 40 meters deep

Electricity transmission main artery: 60

meters deep

18.5km

long

North-

South

tunnel

16.5km

long East-West

tunnel



Cost Comparison

• Median ratio of underground to overhead costs*

– 3.8 to one at 115 kV




• The ratio may go even higher for life cycle cost

that includes maintenance, outage repair costs.


Source: Report of the Joint Legislative Audit and Review Commission To the Governor and

The General Assembly of Virginia “Evaluation of Underground Electric Transmission Lines

in Virginia”, HOUSE DOCUMENT NO. 87 2006, available online http://jlarc.state.va.us/reports/Rpt343.pdf



Overhead/Underground Comparison

Overhead Lines• Lower construction cost and

cable cost.

• Advantage of air for cooling

and insulation of the line.

• Vulnerable to strong wind

and severe weather.

• Negative visual impact.

• Easier maintenance/repair

work

Underground Cables• Expensive pipe work and

cable cost (because of thespecial insulations)

•

Less vulnerable to thesevere weather because it isburied underground.

• Environment and aestheticadvantage.

• Tedious and costlymaintenance/repair work.


What about electrical properties?



Why Three-Phase? (again)




Summary

• Transmission network helps to improve

system efficiency, reliability, and reduce

frequency deviation.

• Advantages and disadvantages of overhead

transmission lines and underground cables




Next Lecture (05/03/2013)

• Four basic parameters of a conductor model.

2/19/2013 EE2022 El t i P T i i b P Ji titij 39

Documents

lectric Power Transmission