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

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Presentation on theme: "APS Underground Distribution Cable Replacement Project Scott Gudeman Manager Const Projects and Support Svcs September 27, 2012."— Presentation transcript:

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 2

3 UG Distribution Cable Historical Overview

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

5 Cable Failures In the mid-1980s, 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 Companys overall SAIFI rating. 5

6 Cause of the Failures The direct buried XLPE primary cable had reached the end of its useful life. Although manufacturers 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

7 Cable Replacement Project

8 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. 8

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 9

10 Cable SAIFI ( System Average Interruption Frequency Index ) Cable SAIFI measures the number of outages customers see each year from cable faults:

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 11

12 Quick Response Cable Replacement – ARs and QHs 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 12

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 13

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 14

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 15

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 16

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 18

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. 19

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

22 Cable Replacement Year to Date 22 Metro Primary Cable Replacement Summary Project YearTrench Miles ReplacedTotal Expenditures 88 thru $22,922, $27,888, $27,568, $23,578, $19,597, $19,662, $18,866, $16,815, $17,857, $18,476, $16,507, $8,014, $10,448, $11,068, $12,345, $13,940, $15,031, $14,601, $13,120, $16,316, $11,563,707 Total2,299.07$356,193,280 * 2012 = Jan - Jul

23 Estimated Direct Buried Cable Remaining Trench Miles (Aug 2012) Division1-1/0A3-1/0A3-750ATotal Metro NE NW SE SW Total

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 25

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 26

27 Questions?


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