APS Underground Distribution Cable Replacement Project

Scott GudemanManager Const Projects and Support Svcs

September 27, 2012

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Agenda

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

UG Distribution Cable Historical Overview

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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 165-180 mil XLPE, non-jacketed type cable.

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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.

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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.

Cable Replacement Project

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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.

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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

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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

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Quick Response Cable Replacement – AR’s and QH’s

Three Phase 3-1/0A CableSingle 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

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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

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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

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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

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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

Replace Vs. Repair

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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

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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.

Where We Are Today

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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

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Cable Replacement Year to DateMetro Primary Cable Replacement Summary

Project Year Trench Miles Replaced Total Expenditures88 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

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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 3 121

SW 135 14 2 151

Total 2320 337 67 2724

Future Direction

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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

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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

Questions?