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Experience you can trust.
Hurricane Hardening
Commission Staff Workshop on Electric Utility InfrastructureRichard E. Brown, PhD, [email protected]
Tallahassee, FloridaJanuary 23rd 2006
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About the Presenter
Richard E. Brown is a management and technical consultant for the electric power industry. He has published more than 70 technical papers related to power system reliability and infrastructure management; is a regular instructor on these topics; is author of the book Electric Power Distribution Reliability; and is a registered professional engineer. He is a senior member of the IEEE, chair of its working group on Distribution Planning and Implementation, and recipient of the Walter Fee Outstanding Young Engineer award. Richard earned his BSEE, MSEE, and PhD from the University of Washington in Seattle, and his MBA from the University of North Carolina at Chapel Hill. [email protected]
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Agenda
Design criteria Hurricanes Hardening
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Power Systems
GenerationPlant
GenerationSubstation
TransmissionTransmission
Substation
Subtransmission
DistributionSubstation
Distributio
nDistributionTransformer
ServiceDrop
Customer
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Should a system be designed to withstand this?
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Design Criteria
National Electrical Safety Code (NESC)– Grades of Construction– Extreme Wind Conditions
Reliability– Sometimes set by regulators– Sometimes set by utilities
Economic– Improve spending efficiency– Spend money to save money
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NESC for Distribution Poles
Freeway crossings “Grade B” Railroad crossings “Grade B” Most other locations “Grade C”
Grade B is 50% stronger than Grade C
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Distribution Pole Strength*
* Grade C is the minimum requirement for most distribution poles. Extreme wind based on 145 mph gusts.
0.0
0.5
1.0
1.5
2.0
2.5
3.0
WoodGrade C
WoodGrade B
Wood(Extreme
Wind)
ConcreteGrade C
ConcreteGrade B
Concrete(Extreme
Wind)
Rel
ativ
e S
tren
gth
.
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HurricanesHurricanes
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Damage
Wind only
Trees
Debris
Flooding
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Wind Only
Hurricane Wilma was strong enough to snap concrete poles
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Trees
Tree damage is usually notpreventable by the utility
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Debris
Flying debris is usually notpreventable by the utility
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Flooding
Flooding can delay restoration efforts
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HardeningHardening
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Wind onPole
Wind Forces on a Pole Wind onConductors
Wind onAttachments
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Design for Extreme Winds
Based on 3-second gusts
Extreme wind rating (equivalent)– Grade B 104 mph– Grade C 85 mph
Florida extreme winds– Southern Coast 145 mph– North Central 95 mph
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Extreme Wind Speeds (3 second gusts)
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Hurricane Categories
0
50
100
150
200
250
1 2 3 4 5Huricane Category
Win
d S
pee
d (
mp
h)
.
1 minute average3 second gust
104
85
145
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“Storm Hardening” Toolkit
Stronger poles More guying Shorter spans Anti-cascading Conductor size Fewer attachments Undergrounding Vegetation management
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Cost of Hardening
New 3-Phase Construction
– Typical Overhead: Typical cost– Hardened Overhead: 2 to 4 times typical– Underground: 5 to 10 times typical
Existing System
– Much more expensive– Much more complicated– Could take 15 to 30 years
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Hardening“Roadmap”
Some Hardening Approaches
Entire system New construction Critical customer facilities Customer-driven Targeted hardening
10-20Years
Now
