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.”

Substation Statistics Voltage # of Substations # of Transformers # of Circuits 2004 Loads Avg. # of Customers 35kV 25 40 119 1851 MW 2401 13kV 51 105 379 1980 MW 817 Ratio 35/13 0.49 0.38 0.31 0.93 2.94

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 Statistics Voltage Average SAIDI SAIFI Total # of Operations Avg. # of Interruptions 35kV 0.2669 .01673 752 6.32 13kV .0442 .00253 965 2.55 Ratio 35/13 6.0385 6.6130 0.78 2.48

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

Conceptual Feeder

Conceptual Performance Example Number of Interruptions Customer Hours Interrupted Feeder SAIDI SAIFI CAIDI 1 3 2400 3.0 1.0 2 6 14400 6.0 10800 4.5 4 9600 4.0

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