Cable Rehabilitation at Oncor by Richie Harp – Distribution Standards Data provided by Mark Darilek – Maintenance Planning SWEDE 2009 – Tulsa, OK – Thursday, May 7, 2009

Cable Rehabilitation Overview  Rehabilitated cable  Cable repairs to facilitate future rehabilitation  Oncor requirements for rehabilitation  Further considerations  2 nd Responder process  Another technology

Amount of Rehabilitated Cable  Began in 1995  420 cbl-mi rehabilitated  8,000 cbl-mi in service – Pre-1993 cable  22,000 cbl-mi total cable

Amount of Rehabilitated Cable  URD  Cable size – Less than #4/0 AWG (#2 and #1/0 AWG, and minimal amount of #2/0 AWG)  Began in 1995  405 cbl-mi rehabilitated  17,000 cbl-mi in service  2% of URD cables

Amount of Rehabilitated Cable  Feeder  Cable size – #4/0 AWG and larger (up to 1000 kcmil)  Began in 2008  15 cbl-mi rehabilitated  3,400 cbl-mi in service  0.4% of feeder cable

Cable Repairs  Standard cable (Began purchasing in 1990)  #1/0 Al 19-Strands  Strand-filled conductors  25 kV, 260-mil TRXLPE  16-#14 AWG Concentric Neutral Wires (Full neutral)  Jacketed

Cable Repairs (Cont)  Only for cable repairs (2-ft pieces) for future injection  #1/0 Al 19-Strands  Strands not filled  25 kV, 260-mil TRXLPE  8-#14 AWG concentric neutral wires (1/2 neutral)  Unjacketed  On 1000-ft composite reel

Oncor Requirements for Rehabilitation  Do not rehabilitate:  Cable installed in conduit  175-mil or 220-mil cable operating at 14.4 kV  Butyl rubber cable  Cable with tape conductor shield  Corroded concentric neutral

 Do not rehabilitate cable if…  Corroded center conductor  Loss of insulation shield conductivity  Insulation shield with no adhesion  Failures due to dig-ins or debris in trench  There is a chance the cable will be converted to 14.4 kV in the future Oncor Requirements for Rehabilitation (cont)

Other Requirements  There must be more than 25% concentric neutral remaining.  There cannot be more that one joint per 100 feet of cable.  The faulted cable section must not have been de-energized more than six months.

Comments:  We tried to rehabilitate some open loops that had been de-energized for up to 2 years  Very little success  We quit rehabilitating open loops that had been de-energized for more than 6 months.

More comments:  2006 and 2007 Processes  Left URD loops open after failures (direct buried cables)  Only repaired cable to get customers’ lights back on.

More comments:  Dec 2007 Process  Began repairing failed loops again.  Caught up with open loops (Feb 2009) – Inject cables or – Replace cable if not able to inject

More comments:  Dec 2008 Process Change  Install joint to repair cable  Try to inject the cable  After the repair, if the cable is not able to be injected, then just leave energized.  Defer replacement of the cable until the next fault.

2 nd Responder Process  System-Wide Process  Repair failures on direct buried cable (not in conduit)  Must be able to switch around to get lights back on.  Not normally feeder exits (Only non-critical cables)

2 nd Responder Decision Process Flow Chart  Available by request

2 nd Responder Process  1868 sections of failed cables came through the process since 2008  749 sections of cable were injected  1119 sections were not able to be injected  922 due to process requirements  197 not related to the process (already energized when arrived, in conduit, etc.)

2 nd Responder Process – Injected/Not Injected

2 nd Responder Process  12 cause codes for not being able to inject the 1119 sections of cable  Age of fault (> 6 months)  Could not flow (Blocked strands or joints)  Inaccessible fault or joint location  Deteriorated neutral (< 25% remaining)  Previously injected, non-warranty or other  Previously injected, warranty

2 nd Responder Process  12 cause codes for not being able to inject the cable (Cont)  Corroded conductor  Number of joints (> than 1 joint per 100 ft)  Unknown  Cable is in conduit  Already energized upon arrival  Other – These last three represent the 197.

2 nd Responder Process – Causes

Another technology  Different formulations for injection fluid  Formulation tailored to operating environment  Tailored more for feeder cables with higher operating temperatures (»45°C)  No soak tanks required  Put back into service immediately after injection

Another technology (Cont)  Must replace all joints  Higher pressures for injection

Rehabilitated Cable That Is Failing  Feeder  URD