1. APS Underground Distribution Cable Replacement Project
Scott Gudeman
Manager Const Projects and Support Svcs
September 27, 2012

2. Agenda UG Distribution Cable Historical Overview
Cable Replacement Program
Replace Vs. Repair
Where We Are Today
Future Direction

3. UG Distribution Cable Historical Overview

4. Background
APS began installing direct buried underground primary distribution cable in the 1950’s and continued until the mid 1980’s.
The majority of direct buried underground primary cable in the APS distribution system is a mil XLPE, non-jacketed type cable.
PILC – Paper insulated lead sheathed cable

5. Cable Failures
In the mid-1980’s, we started to experience a steady increase in direct buried underground cable failures.
There were 0.3 failures for every circuit mile of underground cable, accounting for 24% of the Company’s overall SAIFI rating.
System Average Interruption Frequency Index (SAIFI), it’s used as a reliability indicator by electric power utilities.
IEEE Standard the median value for North American utilities is approximately 1.10 interruptions per customer

6. Cause of the Failures
The direct buried XLPE primary cable had reached the end of its useful life. Although manufacturer’s projected a 30-year life expectancy; we were realizing 16 years.
Contributing factors to cable failures were installation practices, mechanical failures, water trees, accessory failures, manufacturing defects, corrosion, or system overload.
As a result, APS began to install 220 mil, TRXLPE, Jacketed UG cable in conduit in 1986 and fully transitioned to full conduit primary and secondary system in 1988.
A series of tiny hollow voids or channels can develop under electrical stress. These hollow channels are filled with water or materials carried in by water at an earlier time in the cable’s history. Voltage stress over time will cause the small voids to grow. The void will form a small carbon track being burned through the insulation from the phase conductor to the concentric neutral.

7. Cable Replacement Project

8. Cable Replacement Project
The Underground Distribution Cable Replacement Project began in 1992 with the goal of replacing all direct buried underground cable in the APS System.
It has continued since then with the same objective, yet with changing funding levels and business drivers to achieve that goal.

9. Cable Replacement Plan Business Drivers
The Business Drivers used to determine which cable runs to replace:
Customer Satisfaction
Critical Customers and Key Accounts
Operating Demands and Priorities
Number of Faults per Run
Reliability (SAIFI)
Cost Containment
The ‘Z” team came up with a Master Plan

10. Cable SAIFI (System Average Interruption Frequency Index)
Cable SAIFI measures the number of outages customers see each year from cable faults:
SAIFI - System Average Interruption Frequency Index
1.1 North America Avg

11. Replacement Approaches
Utilize a combination of quick response and planned tactics:
Accelerated Replacement (AR) 1-1/0A
Quick Hitters (QH) 3-1/0A
750A and 1/0A Planned Replacement Work
Corroded Neutral Planned Replacement Work
Locate and Repairs
Service/Secondary Replacement

12. Quick Response Cable Replacement – AR’s and QH’s
Three Phase 3-1/0A Cable
Single Phase 1/0A Cable
<= 500’
Not in major street
Not in private easement
Use blanket permit with municipalities
Contract out all excavation and conduit installation
APS crews install and terminate wire
Typically a 7 working day turnaround on jobs with guards

13. Planned Feeder Cable Replacement - 750A
750kCmil Feeder Cable
Jobs are scoped, designed, routed and permits acquired
Budget status determines when job is released for construction
A limited number of jobs are on the shelf so that we can react quickly
Contract all excavation and conduit installation
APS crews install and terminate wire

14. Planned Cable Replacement – Corroded Neutral Cable
1/0A or 3-1/0 in Northern Regions
Concentric Neutral on DB cable has sacrificed itself due to corrosive soil conditions
Jobs to replace multiple runs prioritized by Districts
Jobs are scoped, designed, routed and permits acquired
Budget status determines when job is released for construction
A limited number of jobs are on the shelf so that we can react quickly
Contract all excavation and conduit installation
APS crews install and terminate wire

15. Locate & Repair Single Phase or Three Phase Circuits >500’
In major street
In private easement
Needs a permit to replace
Other complications such as limited access

16. Service/Secondary Cable Replacement
Includes both service and secondary direct buried low voltage (<600 volts) cable runs
Added emphasis in 2011 to replace rather than repair service/secondary faults
Typically, no guards since we can put a service kit on the house
All work is completed by a contractor. They excavate, install conduit and conductor, and re-landscape

17. Replace Vs. Repair

18. Replace Vs. Repair Primary Cable
Philosophy is a balanced approach between Replace and Repair
Mean time between faults accelerates with each failure
2nd Time Fault Recurrence – 3.58 years
3rd Time Fault Recurrence – 2.13 years
4th Time Fault Recurrence – 1.21 years
5th Time Fault Recurrence – 1.40 years
6th Time Fault Recurrence – 0.56 years

19. Replace Vs. Repair Primary Cable
Average cost for Repairs (2011)
$3,800 for 1/0A
$5,800 for 750A
Average Replacement Cost (2011) per work order
$10,190 for 1/0A
$60,108 for 750A
Can replace 1/0A for less than the cost to repair it three times.

20. Where We Are Today

21. How Much Direct Buried Cable Was Installed?
It was estimated that we installed about 5,000 trench miles of direct buried underground primary cable
We have replaced approximately 2,300 trench miles through July 2012
Mid 1960’s through mid 1980

22. Cable Replacement Year to Date
Metro Primary Cable Replacement Summary
Project Year
Trench Miles Replaced
Total Expenditures
88 thru 91
289.57
1992
117.92
$22,922,839
1993
121.26
$27,888,119
1994
180.78
$27,568,844
1995
138.33
$23,578,462
1996
127.70
$19,597,170
1997
148.50
$19,662,976
1998
155.59
$18,866,000
1999
132.83
$16,815,172
2000
130.76
$17,857,885
2001
127.79
$18,476,340
2002
114.71
$16,507,908
2003
75.91
$8,014,052
2004
66.16
$10,448,000
2005
64.18
$11,068,871
2006
55.68
$12,345,972
2007
54.36
$13,940,602
2008
44.12
$15,031,960
2009
30.83
$14,601,760
2010
47.23
$13,120,202
2011
49.21
$16,316,439
2012
25.65
$11,563,707
Total
2,299.07
$356,193,280
* 2012 = Jan - Jul
Much has taken place since my involvement in mid 2008

23. Estimated Direct Buried Cable Remaining Trench Miles (Aug 2012)
Division
1-1/0A
3-1/0A
3-750A
Total
Metro
1444
133 55
1632 NE
288
111 3
402 NW
360 54 4
418 SE 93 25
121 SW
135 14 2
151
2320
337 67
2724

24. Future Direction

25. Going Forward The Cable Replacement Program will focus on:
Replacing all of the direct buried 750A feeder cable in the next 4-5 years
Replacing all identified corroded neutral primary cable (estimated 67 trench miles) in next 7-8 years
Continue with AR and QH program
Mid 1960’s through mid 1980

26. Going Forward
Continue the balanced approach to replace and repair both primary and secondary/service
Advocate funding cable replacement at the same levels as 2012
Primary - $22M
Svc/Sec - $3.5M
Mid 1960’s through mid 1980

27. Questions?