Cibulka_presentation.pdf

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Mitigating the Impacts of ElectricTransmission Linespresented to:

The UC Center SacramentoSacramento, CA

November 1, 2012

by:Lloyd Cibulka

Electric Grid ResearchThis presentation is based in part on work sponsored by the California Public InterestEnergy Research (PIER) program administered by the California Energy Commission; it

does not necessarily represent the views of, nor has it been approved or disapproved by,the Energy Commission.


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Background

Transmission lines in California (and elsewhere) arebecoming increasingly constrained, while load continuesto grow.

Californias RPS goals will put added demands on the

existing transmission system, and will almost certainlyrequire new lines and corridors. Transmission lines are difficult to site and permit, and the

process can take 810 years, far longer than it takes for

renewable generation to be ready. Public opposition to lines tends to focus on their visualand environmental impacts.

2 2012 UC/CIEE uc-ciee.org


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Impacts of Transmission Lines

Physical Right of way (ROW)requirements, construction, etc.

Pollution Ozone, heat, RFI, corona Electric and magnetic fields Hazards to humans and wildlife

Visual

2012 UC/CIEE uc-ciee.org3


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Objectives and Benefits of Using NewTransmission Technologies Increase power-carrying capacity within

existing (constrained) ROWs. Reduce/minimize impacts of transmission

lines: environmental, visual, footprint, etc. Maximize the use of valuable corridors and

transmission assets. Facilitate the siting and permitting processes

for both new lines and upgrades.

while maintaining system reliability and keeping additional costs to a minimum.



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Candidate Transmission Technologies

Re-rating (static) Real-time (dynamic) rating Sagging Line Mitigator (SLiM) Reconductoring Bundled conductors

Single-circuit to double-circuit conversion High-temperature, low-sag conductors Compact lines Voltage uprating Advanced and creative towers & conductors

High phase order design Underground cables (AC) HVDC (conventional) HVDC (new VSC-based) Superconducting cables

C o s t & C

o m p l e x i t y



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Re-rating of Transmission Lines

Re-evaluate line rating assumptions to determine newstatic rating: ambient temperature, wind speed, solarinsolation, emissivity of conductor, line clearance, etc.,according to acceptable level of overloading risk.

The static rating of a transmission line is defined as themaximum sustained current the line can carry and notexceed its limiting temperature or violate its minimumclearance, under the assumed limiting environmentalconditions.

IEEE Standard 738 provides recommendedprocedures and default parameters for performing linerating calculations.



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Static Rating of Transmission Lines



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Re-rating of T/Ls: Pros and Cons

2012 UC/CIEE uc-ciee.org

Pro: capacity increase ~2530%

over static rating withminimal increase of risk

can be used for both

continuous and emergency(contingency) situations no modifications to ROW

required least expensive option (no

hardware upgrades or

monitoring systems) no additional operatingrequirements

no additional visual impacts

Con: need environmental studies or

other analyses to support newassumptions

some physical work may be

needed: splice replacement,re-tensioning, clearanceassessment,relay/transformer/CBupgrades, etc.

slight increase in line losses

possible slight increase in lineoverloading risk possible reduction in conductor

life increase in EMFs, RFI, corona

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Re-rating of T/Ls: Other Constraints


Loading limits on adjacent lines Stability constraints: transient

(disturbances), dynamic (low-leveloscillations, etc.), N1 limitations (RAS &SPS)

Voltage profile

Maintenance and age (loss-of-life) issues

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Dynamic Rating of Transmission Lines


Graphic courtesy of The Valley Group

Use of real-time line and ambient environmental data to produce lineratings closer to actual thermal and clearance limits than staticratings. Also called real-time rating.

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Dynamic Rating of T/Ls: Pros and Cons


Pro: capacity increase up to

100%, depending onconditions and time frame

enables contingency

(emergency) management:takes advantage of short-term overload capability ofthe conductor

if on-line monitors are used,some (very minimal) visualimpacts

Con: may require meteorological

or on-line monitors: cost &maintenance issues,communications, etc.

relay upgrade/re-calibration increased transformerloading

increased line losses increased overloading risk

reduced conductor life increased EMFs, RFI,corona

implementation problematicwith MRTU

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Dynamic Rating of Transmission Lines


Schematic Showing Two Possib le Attachment Loc ations For ConductorGround Clearance/Sag Monitoring Sensors

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SLiM (Sagging Line Mitigator)*


*Developed with support from the California Energy Commission PIER Program.

A device that uses a reverse-temperature tensioning material to

increase transmission line tension, and hence ground clearance andampacity, with increased current (and power).

Photo: Material Integrity Solutions, Inc.


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Reconductoring of T/Ls


Pro: capacity increase ~2X or more

in same ROW no tower mods needed least expensive hardware option

(~$200K/mi for conductors) reduced line losses minimal additional visual

impacts

Con: some line hardware costs: new

clamps, connectors, etc. relaying system upgrades &/or

re-calibration transformer replacement (?)

Replace existing conductors with ones of greater sizeand current-carrying capacity.

Graphic courtesy of 3M Corp.


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Bundling Conductors


Pro: capacity increase ~200% or

more in same ROW may be able to use existing

insulators and crossarms; if

so, costs are similar toreconductoring increase in visual impacts is

not great

Con: relay upgrade/re-calibration transformer replacement or

addition possible insulator, tower &

crossarm upgrades new hardware: clamps,

connectors, spacers increase in EMFs, RFI, and

corona

Add another conductor to an existing conductor (1 ormore per phase).

A B C A B C


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High-Temperature, Low-Sag Conductors


Conductors in which the inner core material carries all the

tension, and the aluminum wires carry almost all the current.Consequently, the conductor can carry more current whilesagging less at higher operating temperatures.

Developed with support from the California Energy Commission PIER Program.


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High-Temperature, Low-Sag Conductors



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High-Temperature, Low-SagConductors: Pros and Cons


Pro: capacity increase of 2X-

5X on existing structuresand ROWs

appearance almostidentical to conventionalconductors

minimal upgrades totowers, crossarms orother hardware

installation techniquesvery similar toconventional conductors

Con: conductors about 5X more

costly per foot than ACSR(but can be used for limitedlengths critical spans)

protection systems will needupgrade/re-calibration

splices need specialattention

increased transformer &adjacent circuit loading increased line losses (%) increased EMFs


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Compact Transmission Lines


Pro: smaller ROWs for reduced

visual impacts existing towers,

conductors and insulatorscan sometimes be used as

is

Con: may require new insulators

and line hardware, e.g.,spacers, crossarms, etc.

maintenance more difficultand expensive, with possiblesafety implications

somewhat increasedcapacitive effects

More or less conventional lattice-tower design, but withreduced spacing between conductors. Typicallyaccomplished with tighter tensioning on more and closertowers, and high-dielectric insulators.


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Single-Circuit to Double-CircuitLine Conversion


Rebuild towers to put two circuits in the same space as one line.

Conventional Single CircuitStructure

Conventional Double CircuitStructure


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Single-Circuit to Double-CircuitLine Conversion: Pros and Cons


Pro: capacity increase ~200%

or more in same ROW EMFs can be lower withproper phasingconfiguration

Con: relay upgrade/re-

calibration transformer addition significant costs for tower

upgrades and hardware higher visual impacts,

RFI, corona increased maintenance

costs


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Voltage Uprating


Pro:

increases capacity by theratio Vnew /Vold existing towers,

conductors andinsulators can sometimes

be used as is decreased losses voltage levels up to

1100 kV in use today

Con:

may require newinsulators and linehardware

transformer replacementrequired

additional visual impacts reactive compensation an

important factor,increases costs

Convert the transmission line from the existing voltagelevel to a new, higher voltage level, e.g., from 115 kV to230 kV.


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High Phase Order Design


Pro: capacity increase

~2X4X (oversingle-circuit line)

feasibility proven atNYSEG in 1997

cost-effective atlonger distances

Con: little actual experience

with this design in US expensive tower design conductor spacers or

limited span lengthsrequired

maintenance issues dueto tight clearancesbetween phases

special phase-shiftingtransformers required atsubstations

Three conventional phases plus three additional phases spaced60 degrees (electrically) between the original phases, in acompact tower arrangement.

Photo: Siemens Corp. and NYSEG


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High Phase Order Design: Spacing

A

B

C

Original 3 Phases: A-B-C120 apartf = 60 Hz

A'

B'

C'

New 3 Phases @ 60: A'-B' -C'

Phase-to-Phase Spacing (Original)

Phase-to-Phase Spacing (New)



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Underground Cables (AC)


Pro: visual impacts are zero EMFs lower than O/H

lines generally more

acceptable in urban andcongested areas

less susceptible to damagefrom storms lower risk of sparking fires no hazard to wildlife,

especially migratory birds

High-pressure gas or oil filled pipe-type cable system [ ].


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Underground Cables (AC)


Con: costs are typically 5X10X that

for overhead lines

construction is difficult, costly andhas environmental impacts maintenance & corrosion issues thermal considerations limit

operation

outages generally more difficultand expensive to repair

potential leakage of SF 6 gas oroil

expensive to upgrade lengths limited to ~40 miles due

to capacitance effects splices are a maintenance and

reliability issue

Solid dielectric cable system [ ].


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HVDC Lines: Pros and Cons


Pro: need only one conductor,

with earth return, to transmitpower

can achieve at least 2X-3Xthe power density as AC in

the same size ROW lower costs than AC fordistances over ~400 miles

no AC no EMFs lower line losses

better control of power flow no practical limit on linelength

can use U/G cables as wellas O/H lines

Con: high costs of converter

equipment need lots of substation

space for converters need lots of reactive

support in the form offilter capacitors more expensive than

O/H AC for distancesunder ~400 miles (butthe economics aregetting better)


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Conversion of AC Line to DC


Pro:

typically ~3X-5X increasein corridor capacity isfeasible, over single-circuit

AC no EMFs

no change in visualimpacts increased control of power

flow no limit on line length

Con: high costs of converter

equipment increased footprint of

substation additional reactive

support required at theconverters (substations)

A 3-phase AC line can be converted to two HVDC lines with a

metallic return, or three HVDC lines with earth return, withoutmodifying the towers, insulators or conductors. Only theterminal equipment changes: AC/DC converters replace thetransformers.


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VSC-based HVDC


Pro: all the benefits of conventional

HVDC, but with lower costs andreactive requirements

can use existing AC lines forconversions

can use solid-dielectric, direct-buried or submarine cables, withlower environmental impacts

4-quadrant operation forenhanced control of power flow

cables can easily be direct-buried under existing AC linesor in other ROWs (highwaymedians, railroads, etc.)

Con: at present, voltage limited to

300 kV, power to ~500 MWper circuit

fairly new technology withrelatively positive, albeitlimited, operating experience

still relatively expensive,compared to conventionaloverhead AC

An HVDC technology using voltage-source converter (VSC)power electronics instead of line-commutated high-powerthyristors.


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HVDC Lines in Highways



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HVDC Lines in Electric Rail ROWs



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High-Temperature SuperconductingCables


Pro: ~10X the power capacity of

much larger conventionalcable systems

no EMFs, even with ACoperation

zero losses, except forcryogenics

niche market applicationsbeing demonstrated today

Con: very expensive at present still a developing technology

limited to runs of < 1 mile splices are very tricky forlonger runs

cryogenics improvementsneeded

Transmission cables constructed ofsecond-generation (2G)superconducting wire in a liquidnitrogen bath.


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Tower Structures



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Blending In


Shiny vs. weathered conductors; lattice vs. pole; bare metal pole vs. painted.


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Topographic Background Integration



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Foreground Landscape Screening



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Landscape Background Integration



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Big & Bold Designs



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Anti-Camouflage Tower



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Other Creative Tower Designs



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Towers That Look Like Us


Choi + Shine Design for Iceland Design Competition


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Towers That Look Like Us


Choi + Shine Design for Iceland Design Competition


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Questions?

Lloyd CibulkaCalifornia Institute for Energy &

EnvironmentElectric Grid [email protected]

SAIC

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Cibulka_presentation.pdf