Cable Rehabilitation at Oncorby Richie Harp – Distribution StandardsData 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

2nd 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 minimalamount 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.

2nd 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)

2nd Responder Decision Process Flow Chart

Available by request

2nd 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.)

2nd Responder Process – Injected/Not Injected

922

749 Injected

Non-Injected

2nd 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

2nd 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.

2nd Responder Process – Causes

11%

11%

20%

16%

5%

18%

1%

3%

1%

2%

4%8%

Age of fault

Could not flow

Inaccessible fault or joint

Deteriorated neutral

Number of splices

Previously injected, non-warrantyPreviously injected,warrantyCorroded conductor

Unknown

Cable in conduit

Energized upon arrival

Other

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