1. 35kV Assessment
SWEDE 2007
May 10, 2007

2. 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

3. 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

4. Major Items Past system costs & expansion Reliability
Linear capacity optimization
Automation
Backbone philosophy
Progress and performance measurement

5. 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.”

6. 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

7. 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

8. 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

9. Reliability Drivers Number of Customers Protection Philosophy
Construction Standards
Others – length, equipment, procurement, conductor size, construction to engineering feedback

10. 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

11. Protection Philosophy
Breaker, fuses & sectionalizers
Limited use of reclosers
Large fuses for URD loops
Limited breaker reclosing

12. Construction Standards
BIL of structures
Grounding
Topology
Stress due to faults

13. Conceptual Feeder

14. 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

15. 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

16. 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