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35kV Assessment. SWEDE 2007 May 10, 2007. Mission/Objective. Review original decisions to utilize 35kV Review Oren E. Park Report from 1971 Understand the comparison of 13 & 35kV Performance, reliability & costs Review Navigant Findings from 2003 Review CPS Planning Guidelines for 35kV
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35kV Assessment SWEDE 2007 May 10, 2007
Mission/Objective • Review original decisions to utilize 35kV • Review Oren E. Park Report from 1971 • Understand the comparison of 13 & 35kV • Performance, reliability & costs • Review Navigant Findings from 2003 • Review CPS Planning Guidelines for 35kV • Formulate an approach going forward to maximize performance and reliability to 35kV system • Align with EDS strategy
Team Members • Les Barrow – Planning & Reliability Engineering • Albert Lara – Reliability Planning • Dwain Duke – Reliability Planning • Rick Maldonado – Substation & Dist Planning • Sam Le - Substation & Distribution Planning • George Tamez – Overhead Engineering • Blake Williams – Underground Engineering • Joe Rodriguez – Substation Design
Major Items • Past system costs & expansion • Reliability • Linear capacity optimization • Automation • Backbone philosophy • Progress and performance measurement
Parks’ Assertions • Reduce number of substations • Reduce number & size of feeders • Reduced transmission right-of-way needs • Lower reliability with higher voltage • “Standards of safety and reliability enter into the comparison, and they will temper to some degree the attractiveness of the higher voltage resulting from the economic gain.”
Estimated Costs • Substation & Transmission savings • 25 substations at $2M = $50M • 10.6 mile/substation at $500k = $132.5M • Distribution added costs • Overhead: 2435 miles at $6,500/mi = $15.8M • Underground: 2435 mi at $12,000/mi = $29.2M • Net $50M + $132.5M - $45M = $137.5M
Reliability Drivers • Number of Customers • Protection Philosophy • Construction Standards • Others – length, equipment, procurement, conductor size, construction to engineering feedback
Number of Customers • 35kV feeder approximately three times number of customers as 13kV • 35kV feeder approx. twice 13kV length • No significant protection differences • 3 times customer * 2 times length = 6 times • Reliability Indices concur
Protection Philosophy • Breaker, fuses & sectionalizers • Limited use of reclosers • Large fuses for URD loops • Limited breaker reclosing
Construction Standards • BIL of structures • Grounding • Topology • Stress due to faults
Capacity, Automation, Backbone • Linear capacity optimization - relationships of all physical components need to be reviewed for optimum utilization • Automation - utilize intelligent reclosers, switches & schemes • Backbone philosophy – required foundation • Progress and performance measurement
Recommendations • Distribution Planning to review customer number/circuit • Protection changes • Aggressive recloser installation project • Smaller fuses on smaller URD loops • Review all sectionalizers • Concurs with multi-shot approach • Construction design standards review • Investigation of linear capacity optimization by Distribution Planning • Implement backbone philosophy with automation • Progress and performance measurement by Reliability Planning