Assessing, Maintaining & Replacing Fluid Filled Cable Systems at PEPCO

Transcription

1 April 2, 2014 Assessing, Maintaining & Replacing Fluid Filled Cable Systems at PEPCO Todd Goyette, P.E., POWER Engineers Mousa Hejazi, P.E., Pepco Holdings Inc. 1

2 Pepco Quick Facts First incorporated in 1896 Service territory: 640 square miles Customers served: 793,000 Washington, D.C.: 260,000 Montgomery County: 309,000 Prince George s County: 225,000 Population served: 2.2 million 2

3 Purpose Comprehensive review of PHI s oil impregnated paper insulated cable systems Limited & decreasing number of manufacturers of cable Limited & decreasing number of manufacturers of cable accessories (reservoirs, pumping plants, etc.) Decreasing numbers of qualified splicers to work with these types of cables Environmental impact of fluid leaks 3

4 Approach Review separated into 3 tasks Task1: Industry Survey Determine current trend of industry with regards to maintaining or replacing these legacy cables systems Task 2: Cataloging Existing Systems Develop a complete list of the cable systems on PHI s system o Identify components and key drivers (type, voltage, length, age, etc.) for use in future studies and planning 4

5 Approach Task 3: Risk & Condition Assessment Develop risk matrix to qualitatively and quantitatively identify areas of risk for these types of cable systems Identify areas of possible improvements to mitigate risks 5

6 Background: Self Contained Fluid Filled Cables (SCFF) Developed in 1920s Uses dielectric fluid under pressure to maintain insulation integrity Pressure maintained by reservoirs installed in manholes and substations Cable sheath acts as pressure vessel & hermetic seal 6

7 Background: Self Contained Fluid Filled Cables (SCFF) Relies heavily on no air or moisture entrainment Two subcategories Low Pressure Fluid Filled (LPFF) Operating pressures 1-15 psig Typically lead sheath Medium Pressure Fluid Filled (MPFF) Operating pressures 5-70 psig Typically aluminum sheath or reinforced lead 7

8 Sample SCFF Cables 8

9 PHI Self Contained Fluid Filled Cables # of Circuits 69kV 115kV 138kV 230kV Total Low Pressure Fluid Filled Medium Pressure Fluid Filled Total Mileage 69kV 115kV 138kV 230kV Total Low Pressure Fluid Filled Medium Pressure Fluid Filled Total PHI has 32 SCFF systems and Approximately 103 circuit miles of SCFF cable 9

10 Background: High Pressure Pipe Type Cables (HPPT) Historically most common type of transmission cable installed in the United States Gained popularity after World War II Three cables installed in a coated steel pipe Requires pressurizing plants to maintain a nominal pressure of 200 psig Courtesy of the Okonite Company 10

11 Background: High Pressure Pipe Type Cables (HPPT) Requires active cathodic protection to prevent pipe corrosion Two subcategories High Pressure Fluid Filled (HPFF) High Pressure Gas Filled (HPGF) Courtesy of the Okonite Company 11

12 PHI High Pressure Pipe Type Cables # of Circuits 69kV 115kV 138kV 230kV Total High Pressure Gas Filled High Pressure Fluid Filled Total Mileage 69kV 115kV 138kV 230kV Total Low Pressure Fluid Filled Medium Pressure Fluid Filled Total PHI has 90 HPPT systems and Approximately 322 circuit miles of HPPT cable 12

13 Task 1: Industry Survey 13

14 Industry Survey Questionnaire sent to utilities across the United States 29 questions covering a range of topics Existing Cable Systems New Cable Systems Proposed Cable Systems Replacement Cable Projects Electrical Failures Circuit Availability Maintenance Practices Contractor Usage Spare Material Future Risk Concerns 14

15 Industry Survey Results PHI has one of the larger inventories of active SCFF & HPPT cable systems (both by number and mileage) Utilities are actively seeking to reduce their self contained fluid filled cable inventory Age, reliability concerns, capacity Utilities are not actively seeking to replace their high pressure pipe type circuits High Voltage Extruded Dielectric (XLPE & EPR) is becoming more popular for new installations HPPT cable is still considered a viable option for certain conditions There is a growing industry concern with the limited number of manufacturers & contractors for oil impregnated paper insulated cables & accessories 15

16 Task 3: Risk Matrix Development & Evaluation 16

17 Risk Matrix Development Cable systems evaluated on various criteria Cable Construction Installation Conditions Planning Drivers O&M Practices Operation Spare Material Physical Condition Assessment Criteria further separated into various subtopics 17

18 Self Contained Fluid Filled Cables Condition Assessment, Risk Evaluation & Recommendations 18

19 SCFF Condition Assessment April 15 19, 2013 Visual inspection of cables and accessories Terminations Splices Reservoirs Pressure Gauges & Alarms Exposed Cable Fluid Leaks and other possible problems noted Equipment & overall location condition given a ranking of good, fair or poor based on observations 19

20 SCFF Condition Review Sample of Issues Observed 20

21 SCFF Condition Review continued 21

22 SCFF Cable & Terminations Condition Majority of Terminations are in good condition 22

23 SCFF Reservoirs Condition Very few problems with fluid reservoirs were observed 23

24 SCFF Overall Condition Overall condition of SCFF cables is fair to good 24

25 PHI SCFF Cable Risk Results 25

26 Conclusions / Recommendations PHI SCFF cable systems are considered to be in fair to good condition PHI still encouraged to develop a system program to replace these oil filled cable systems Current industry trend is to install extruded dielectric at these lower voltages (69kV & 138kV) Limited availability of manufacturers and qualified workers Expected further decrease in these numbers 26

27 Conclusions / Recommendations Increased costs of operation & maintenance Increase risk of circuit unavailability due to leaks & electrical failures Increased risk of environmental impacts cause by fluid leaks Increased risk of potential health impacts due to working with identified hazardous material (lead). 27

28 Replacement Strategy Use Risk Matrix rankings to prioritize projects High Priority circuits should have projects initiated within 5 years Medium Priority circuits should have projects initiated within years Low Priority circuits should be targeted for after 15 years 28

29 Replacement Options Three Options Considered Option 1: Replace with HVED cable systems Eliminates ongoing environmental concerns with dielectric fluid Reduces future O&M needs and costs Requires significant civil infrastructure improvements o New manhole and duct system required Estimated order of magnitude costs: $312M 29

30 Replacement Options Option 2: Re-Conductor with SCFF cables Eliminates any concerns with existing age or condition of cables Least cost solution o Can Utilize existing manhole & duct system Does not eliminate environmental concerns with dielectric fluid Does not reduce future O&M needs or costs Estimated order of magnitude costs: $90M 30

31 Replacement Options Continued Option 3: Develop direct replacement HVED cable Partner with a high voltage cable manufacturer to develop a 3/C HVED cable that will fit in the existing manhole & duct system Combines the advantages of both Option 1 & Option 2 Requires some engineering & developmental costs for cable & accessory design and testing Various cable manufacturers have expressed intent to develop solid dielectric cables capable of direct replacement 31

32 High Pressure Fluid Filled Cables Condition Assessment, Risk Evaluation & Recommendations 32

33 HPFF Condition Assessment May & July 8 10, 2013 Visual inspection of cables and accessories Terminations Pressurizing Systems Cathodic Protection System Exposed Pipe Fluid Leaks and other possible problems noted Equipment given a ranking of good, fair or poor based on observations 33

34 HPFF Condition Review Sample of Issues Observed 34

35 HPFF Condition Review Sample of Issues Observed 35

36 HPFF Terminations Condition Majority of Terminations are in good condition 36

37 HPFF Terminations Condition Majority of Terminations are in good condition 37

38 HPFF Terminations Condition Majority of Terminations are in good condition 38

39 HPFF Pressurizing Plants Condition Majority of Pressurizing Plants are in fair to good condition 39

40 PHI 69kV HPFF Cable Risk Results 40

41 PHI 115kV & 138kV HPFF Cable Risk Results 41

42 PHI 230kV HPFF Cable Risk Results 42

43 Conclusions / Recommendations PHI HPFF cable systems are considered to be in good to very good condition Small number of 69kV circuits are considered at a medium risk Mostly attributable to condition of pressurizing plants Continue with ongoing replacement program for pressurizing plants Consider adding additional pressurizing plants to list 43

44 Conclusions / Recommendations Continue with good maintain practices Active cathodic protection systems to prevent pipe corrosion Oil sampling and DGA analysis on periodic basis to identify incipient problems Continue to monitor pipe type cable replacement options for future consideration Re-evaluate cable condition on periodic basis 44

45 PHI s Additional Replacement Factor Considerations Replacement factor increase for SCFF Cable failure Outage within past 5 years warrants increase in replacement factor Feeders with short lengths increase replacement factor due to increased feasibility and lower cost Redundancy increases the replacement factor 45

46 PHI Replacement Strategy Coordinate risk matrix rankings with strategic plans from other departments Transmission Planning Electric Construction & Maintenance System Operations Look for synergy between circuits with common routes to maximize efficiencies of design & construction 46

47 Questions This concludes the educational content of this activity Thank you for your time! Todd Goyette P.E. Senior Project Engineer POWER Engineers Mousa Hejazi, PE. Senior Supervising Engineer Pepco Holdings Inc