Underground Cable Failure Tracking Underground Cable Failure Rates. Jon Erickson San Diego Gas & Electric. ICC Educational Program November 3, 2004

Transcription

1 Underground Cable Failure Tracking Underground Cable Failure Rates Jon Erickson San Diego Gas & Electric ICC Educational Program November 3, 2004

2 Topics Background on SDG&E electric system Cable failure tracking method Data collection Cable failure database Cable failure rates Use of cable failure database Statistical method for determining failure rates Examples of cable failure rates Feeder and branch circuit reliability model

3 SDG&E Electric System 2003 totals Number of electric customers 1,290,168 Number of electric distribution circuits kv circuits kv circuits 690 Underground cable circuit miles 8882 Underground cable conductor miles 22059

4 SDG&E Electric System (cont). Unjacketed HMWPE cable miles 3700 Installed Remaining HMWPE cable miles 3260 Unjacketed XLPE cable miles 3400 Installed Remaining XLPE cable miles 2969 Jacketed XLPE/TRXLPE cable miles Installed XLPE Installed TRXLPE 1998 to present Jacketed EPR cable miles 130 PILC cable miles 189

5 SDG&E Electric System (cont). 57 % of system underground 99+ % of cable in conduit or cable in conduit Cable failure replacement all cables in conduit replaced

6 Cable Failure Tracking Use Distribution System Operating Report Research failed segment Identify segment on operating map Determine work order installation date Obtain equipment failure report from operating district Enter data in cable failure database

7 Distribution Systems Operating Report

8 Underground Operating Map

9 Work order Information

10 Equipment Failure/Problem Report

11 Cable Classification Feeder cable Branch Cable 350 Al # 4 Cu 4/0 Cu # 2 Cu 500 Cu # 2 Al 750 Al 2/0 Al 750 compact Al 1000 Al

12 Cable Failure Database

13 Cable Failure Database

14 Monthly Cable Failure Report September 27, 2004 MONTHLY CABLE FAILURE REPORT (12KV) August 2004 YTD 2 REPORTED DIG-INS IN AUGUST 2004 CIRCUITS 402, FEEDER FAILURES: DATE SUBSTATION/CKT/DST CABLE TYPE MG/DATE W/O # W/O DATE 8/15/04 MIRAMAR/761/BC 750 AL XLPE /74 8/29/04 ROSE CANYON/65/BC 750 AL XLPE /71 8/31/04 MELROSE/507/NC 750 AL XLPE /80 NO JACKETED LATERAL CABLE FAILURES IN AUGUST 2004

15 Determining Cable Failure Rates Need to know amount and type of cable (HMWPE, XLPE, TRXLPE, EPR, jacketed) installed in a certain year. Need to know the amount and vintage of the cable that failed. Need to convince your operating people of the importance of collecting cable failure information. Need to develop a simple method of collecting cable failure data. Need to be able to account for any proactive cable replacements. Maintain an outage database (Access database). Utilize statistical software ( i.e. Weibull ++) to determine best fit for your data. Projections should include data confidence bounds ( i.e. 90%).

16 Cable Failure Projections (2003)

17 Cable Failure Projections (2004) Cable Failures vs Time - Best Fit All Cable Predicted All Cable Actual HMWPE Predicted HMWPE Actual XLPE Predicted XLPE Actual Nbr of Failures Year

18 Cable Failure Projections (2003)

19 Cable Failure Projections (2004) Actual Cable Failures per Year 2002 & 2003 Fit with & without Proactive Replacements Number of Failures All Cable HMWPE XLPE 2002 All Fit 2002 HMWPE Fit 2002 XLPE Fit 2002 All Proactive Fit 2003 All Fit 2003 All Proactive Fit Year

20 Cable Failure Rates (2003) 0.7 SUMMARY OF ALL HMWPE, XLPE AND WORST VINTAGE LATERAL UG CABLE FAILURE RATE (UPPER 90% PREDICTED VALUE) 0.6 HMWPE LATERAL 90% Pred Lim HMWPE FEEDER 90% Pred Lim 1.59 FAILURE / CIR MILE (X-L)** 1.35 FAILURE / CIR MILE (X-L) # OF FAIL / COND MI REMAINING XLPE FEEDER 90% Pred Lim XLPE LATERAL 90% Pred Lim WORST HMWPE LATERAL 90% Pred Lim* WORST XLPE LATERAL 90% Pred Lim** FAILURE / CIR MILE (H-L)* 0.45 FAILURE / CIR MILE (X-F) 0.36 FAILURE / CIR MILE (H-F) 0.25 FAILURE / CIR MILE ((H-L) YEAR

21 Cable Failure Rates (2004) Summary of HMWPE, XLPE and Worst Vintage Lateral UG Cable Failure Rate (Upper 90% CL) Failures/Conductor Miles Rem aining HMWPE Feeder XLPE Feeder HMWPE Lateral XLPE Lateral Worst HMWPE Lateral Worst XLPE Lateral 2.03 F/Cir Mi XL Worst 0.62 F/Cir Mi XL 0.37 F/Cir Mi Hl Worst 0.37 F/Cir Mi XF F/Cir Mi HF 0.26 F/Cir Mi HL Year

22 Branch Circuit Reliability Model Failure rates by conductor mile in outages/year Options CAIDI Gain Units Other Constants Cable Type All vintages Bad vintages Sub-Fusing N/A N/A System Average CAIDI (min) 217 XLPE-PEJ N/A Looping 48 minutes System Customers 1,300,000 XLPE Fault Indicator Addition 20 minutes LACC Factor HMWPE Cable Change Out N/A N/A Annualized Cost Savings per circuit foot: Phase Cable Type vintages Bad vintages $ 6.50 Single phase XLPE $ 3.40 $ 3.96 Cable Replacement Cost $ phase Looping HMWPE $ 0.63 $ 0.95 (per foot) $ phase Item Phase Quantity DO NOT CHANGE ANY DATA ABOVE THIS GRAY LINE. Single - Cable Change Out Sub-Fusing Main Branch Total Footage2-phase - Item Phase Quantity Item Phase Quantity 3-phase - Single - Single - Failure Rate Main Branch Total Footag 2-phase - Main Branch Total Footage 2-phase - Branch Total Customers phase - 3-phase - Project Cost $ 25,000 Single - Single - SAIDI Gain - Replaced Branch Footage 2-phase - Sub-fused Branch Footage 2-phase PBR Gain $ - 3-phase - 3-phase - RTR Failure Rate Failure Rate Annualized Cost Savings Rate $ 3.96 Branch Total Customers 272 Fault Indicator Addition Branch Total Customers 272 Sub-fused Branch Customers 58 Item Phase Quantity Cable Replacement Cost $ - Project Cost $ 25,000 Single - Other Costs $ - SAIDI Gain - Main branch total footage 2-phase - Project Cost $ - SAIFI Gain - 3-phase - Gain In Number of Failures PBR Gain $ - Failure Rate SAIDI Gain - RTR Branch Total Customers 272 SAIFI Gain - Project Cost $ 8,000 PBR Gain $ - SAIDI Gain - Annualized Cost Savings $ - PBR Gain $ - RTR RTR d INPUT IS ONLY REQUIRED IN THE TAN CELLS.

23 Feeder Circuit Reliability Model