Underground vs. Overhead Transmission TOTL Citizen Advisory Group - - PowerPoint PPT Presentation
Underground vs. Overhead Transmission TOTL Citizen Advisory Group April 15, 2015 Transmission and Distribution Transmission System Distribution System Transmission lines Distributes electricity connect power to each customer's
TOTL Citizen Advisory Group April 15, 2015
Transmission lines
Distributes electricity
Transmission System Distribution System
Transmission Distribution
Undergrounding
Underground cables
Undergrounding
Transmission Distribution
Design Construction Repair and Maintenance Cost Aesthetics
Design Issues
Specialized engineering skills required Extensive study required to determine site-specific
Longer timeframe for design Need to provide larger budget contingency Flood plain and wetland issues require special
Environmental impacts
Construction Concerns
Space for large vaults (8’ x 10’ X 20’) Longer construction time frame Dewatering in wet areas during construction Significantly more impacts to surrounding properties
Open trenches
min. 5’ wide x 5’ deep
Specialized backfill
Operational Concerns
Difficult to identify outage location Requires specialized work force Long lead time for delivery of materials
Need to warehouse specialized spare materials
Increased maintenance Shorter life span Dewatering and cleaning of equipment in vaults
Cost
Typical underground costs are 8 to 10 times the cost of
Typical life of underground is approximately one-half the
Depending on route may have significantly more
4-Cable system required to increase reliability which adds
Specialized workforce increases cost Wetland mitigation may be substantially more depending
Warehousing of spare materials and equipment
Generally used:
in densely populated and urban settings where sufficient right-of-way is not available to reduce visual impacts
riser poles at each end of the underground cable are large
Reliability
May have fewer outages than overhead When outages occur they will be more difficult to