SM SOUTHERN CALIFORNIA EDISON® Together, Making T&D the Safest Place to Work Cable-in-Conduit (CIC) Challenges and Strategies NameSeema Abraham TitleSenior

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SOUTHERN CALIFORNIA EDISON®

Together, Making T&D the Safest Place to Work

Cable-in-Conduit (CIC)Challenges and Strategies

Name Seema Abraham

Title Senior Project Manager

Reliability & Infrastructure Replacement

Southern California Edison

CONFIDENTIAL – Use subject to terms of utilities Confidentiality Agreements

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Southern California Edison

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• 50,000 square miles• ~ 76 billion kWh/year delivered • 4.9 million customers• Over 400 cities & communities

with a collective population of over 13 million people


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Distribution Assets

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1,440,000 wood poles

50,000 cond-miles of UG primary conductor

106,000 cond-miles of OH primary conductor

715,000 distribution transformers

87,000 padmount/subsurface switches

2,800 substation transformers

10,500 substation circuit breakers

4,600 distribution circuits (mostly radial design vs. looped)


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SCE Org Structure

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Distribution Business Line

SCE SVP of T&D

Engineering & Tech Svc

Transmission, Substation, and

Operations

Major Projects Organization

Asset Management

Description

Responsible for distribution

network, vegetation

management and field accounting

Responsible for grid

operations, substation, and

transmission activities

Oversee system planning,

engineering, and design

Develop strategies for deployment, maintenance

and replacement

of T&D assets

Oversee the development of

SCE’s major transmission

and substation projects

Sub organizations

• Distribution construction and maintenance by region

• Design & Field Accounting

• Pole assessments

• Programs & strategies

• Substation construction and maintenance by region

• Transmission construction and maintenance by region

• Grid operations

• Edison Carrier Solutions

• Engineering

• System planning

• Real properties

• Advanced technology

• Maintenance, performance, reliability

• Contracts

• Business planning

• Business effectiveness

• Project governance and admin

• Major projects such as Tehachapi wind project


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How is Reliability Measured?

Momentary Outages:Outages lasting 5 minutes or less

• MAIFI: – The number of times the

average customer is interrupted by Momentary outages each year.

• SAIFI:– The number of times the

average customer is interrupted by Sustained outages each year.

• SAIDI:– The cumulative amount of

time the average customer is interrupted by Sustained outages each year.

Sustained Outages:Outages lasting longer than 5 minutes


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Problem = Aging Equipment


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50,000 conductor-miles of Distribution UG primary cable______________________________

37,000 miles in rigid duct (e.g., PVC, transite, soapstone, etc.) most unjacketed

13,000 miles in polypropylene tubing all unjacketed = > CIC


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Miles of CIC Expected to Wear-out Each Year

The current in-service failure volume of CIC ≈ 50 cond-miles.Unaddressed, this will increase six-fold within 30 years.


Co

nd

-mil

es

Year

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Cable-in-Conduit

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Example of 220mil XLP (#2xlp) and the 1.5” CIC Duct

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The Problems of CIC

Installed as a radial system (no looped ties):

Limited operational flexibility Increasing number of in-service failures:

Mean-time-to-failure = 41 years20% of CIC population is older than MTTF

Significant impact on reliability:

Typical outage caused by CIC failure ~ 20 hours

Very high cost of replacement:

Historical replacement via trenching = $800,000 /mile


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12,000 conductor-miles of CIC will exit the system before the year 2065

1. Wholesale replacement of entire radials based solely on failure history

3. Run to failure

Rigid duct via Directional Boring

Use existing duct via lube cartRigid duct

installed via trenching

Cable Rejuvenation


2. Selective replacement of only cable segments determined “bad” via PD testing

Rigid duct installed via trenching


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12,000 conductor-miles of CIC will exit the system before the year 2065

Wholesale replacement of entire radials based solely on failure history

Run to failure


Use existing duct via lube cartRigid duct

installed via trenching

Cable Rejuvenation


Selective replacement of only cable segments determined “bad” via PD testing



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Partial Discharge Testing – Why cable fails?

Cable SystemFailureInner Conductor

Outer Conductor

Insulation

Basic Cable Design

Operational Risk Factors1.Over-voltage events

i. Breaker/Fuse reclosuresii. Fault locatingiii. Lightning

2.Long out-of-service periods3.Over-voltage protection

i. Placement in circuitii. Sizing and Installationiii. Circuit Configuration

4.Accessory contamination5.Open air terminations


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Partial Discharge Testing – The Standards

TerminationsIEEE 48

Joints IEEE 404

Separable Connectors IEEE 386

MV Extruded CableANSIICEA S-97/94-682/649

HV / EHV Extruded CableANSIICEA S-108-720

≤ 1.5 Uo

≤ 1.5 Uo

≤ 1.3 Uo

≤ 4.0 Uo^

≤ 2.0 Uo

The Manufacturers’ Standards

* No partial discharge should be observable above the sensitivity threshold up to the voltage threshold

^200 V/mil

Component Standard SensitivityTesting

Frequency5pC

5pC

3pC

5pC

5pC

50/60 Hz

50/60 Hz

50/60 Hz

50/60 Hz

50/60 Hz

Voltage


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Concentric NeutralsNeutral Corrosion AssessmentDefect Specific Neutral Corrosion Diagnostic (HRTDR) Time Domain Reflectometer

HRTDR Level Wires Broken Wires Remaining SCE Priority HRTDR Response

1 0% to 25% 75% to 100% Good<25% of the roundtrip reflection

No significant mid-span imped. inflect.

2 25% to 50% 50% to 75% 225% - 50% of round trip reflection

Smaller than a typical splice reflection

3 50% to 75% 25% to 50% 250% -100% of the round trip reflection

Larger than a typical splice reflection

4 75% to 100% 0% to 25% 1 Larger than the round trip reflection

Reference: IEEE 1617 Table 1 Corrosion Categories

Distributed Neutral Corrosion Assessment (BSIR)BSIR Level General Neutral Condition SCE Priority BSIR Response

ANo recognizable distributed neutral corrosion

Good

Identifiable roundtrip of 20pC or better (smaller)

No significant signal attenuation

BSubstantial distributed neutral corrosion

2Identifiable roundtrip between 50 and 500pCSubstantial signal attenuation

C Severe distributed neutral corrosion 1

Identifiable roundtrip of 500pC or greaterNearly complete or complete signal attenuation

Reference: IMCORP BSIR specification: Please consult IMCORP for more information.

Matrix Based on SCE Deteriorated Concentric Neutral Document - Phase to Ground HRTDR Result

BSIR 1 2 3 4

A Good Long Term Replacement Long Term Replacement Short Term Replacement

B Long Term Replacement Long Term Replacement Long Term Replacement Short Term ReplacementC Short Term Replacement Short Term Replacement Short Term Replacement Short Term Replacement

Matrix Based on SCE Deteriorated Concentric Neutral Document - Phase to Phase HRTDR Result

BSIR 1 2 3 4A Good Long Term Replacement Long Term Replacement Long Term ReplacementB Long Term Replacement Long Term Replacement Long Term Replacement Long Term ReplacementC Long Term Replacement Long Term Replacement Long Term Replacement Long Term Replacement


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SCE’s Pass Criteria

Concentric neutrals must have a rating of 1A

No insulation PD at less than 2.5 times the operating voltage

No termination PD at less than 1.5 times the operating voltage

No splice (joint) PD at less than 1.5 times the operating voltage

No connection PD at less than 1.3 times the operating voltage


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Partial Discharge Testing @ SCE

2009 and 2011 – Limited scope pilot

September 2012 – Broader scope pilot

Q1/2013 – Initiated Partial Discharge Testing as a program

~7800 cable segments tested to-date

0.8% 44.1% 55.1%

Insulation Identified for No ReplacementFailure & Replacement NeededEmergency Replacement

40.2% Insulation50.7% Concentrics30.5% Splice/Termination* Not Exclusive


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Partial Discharge Testing @ SCE

Pros & cons of Testing

Benefits:+Provides an assessment of the asset in the ground+Cost effective since testing allows replacement of only those segments that are known to be defective

Issues / Challenges:KOccasional testing induced

failure (~1%)KRequires an outageKTime between completion of test

and actual replacement of “bad” segment


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Cost of Replacement % Required to Pass to “Break Even”

$800,000 / cond-mi 5%$500,000 13%$400,000 17%$300,000 21%$200,000 32%$150,000 50%

Comparing the NPV of the revenue requirements for a) replacing all cable immediately without testing versus b) testing all cable, replacing immediately only the “bad” cable, and replacing the “good” cable exactly 10 years in the future, all assuming cost of testing program

Cost-Effectiveness of Cable Testing

Note: As the CIC ages, the “pass” rate will decline to the point where testing will no longer be cost-effective. At that time, we will simply replace all CIC.

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Cable Rejuvenation

What is Cable Rejuvenation?

Cable Rejuvenation is technology that injects an engineered, silicone-based fluid into spaces between the cable strands of underground medium-voltage cable under low to moderate pressure. The fluid then migrates into the conductor shield and insulation to restore the cable to better-than-new performance.


Methods of Rejuvenation

Sustained Pressure Rejuvenation (SPR)Used when no splices are present. All accessories are replaced and cable is injected under moderate pressure to return the cable to its full dielectric strength. Extends cable life up to 40 years.

Un-sustained Pressure Rejuvenation (UPR)Used when the segment of cable has one or more splices. An airflow test is performed to confirm fluid will flow. Uses low pressure to flow fluid through splices when cable is energized. Extends cable life up to 25 years.

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Cable Rejuvenation @ SCE

2013 – Limited scope pilot

October 2014 – Second pilot

May 2015 – Broadened pilot scope to rejuvenate complete circuit(s)

2014 – Targeted rejuvenation of ~45,000’

0.0% 80% 16% 4%

Failure Successfully Identified as Identified for & Rejuvenated newer strand ReplacementEmergency filled cableReplacement


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Pros & Cons of RejuvenationWholesale replacement of entire radials based solely on failure history

Run to failure Rigid duct via Directional Boring

Use existing duct via lube cart


Cable Rejuvenation


Selective replacement of cable segments determined “bad” via PD testing


Benefits:

+Promises to extend cable life by up to 40 years

+All terminations are replaced


Issues / Challenges:

KCannot be performed on segments with splices between BURD’s

KUncertainty over effectiveness

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CIC Replacement @ SCE

1. Replacement of cable in existing polypropylene tubing

2. Installing rigid duct using Directional Boring

3. Traditional method of installing duct using trenching


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Replacement in existing duct using new methods


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Pros & Cons of using existing ductWholesale replacement of entire radials based solely on failure history




Cable Rejuvenation




Benefits:

+Least expensive of all options (when it works)

+No need for easements

+New “Flat-Strap” cable should have a MTTF of 46 years


KRequires a second (after testing) outage

KDoes not always work

KOperations perception that this is a “band-aid” and not a long term solution (vs installation of rigid duct)


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Pros & Cons of replacement using Directional BoringWholesale replacement of entire radials based solely on failure history




Cable Rejuvenation




Benefits:

+Potentially faster and much less expensive than trenching

+Limited noise and surface disruption with construction activity mostly at access points

+Widely used by utilities across the U.S.

+Results in installation of rigid duct


KNot applicable in all scenarios

KReluctance within SCE


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Pros & Cons of Traditional Replacement

Wholesale replacement of entire radials based solely on failure history


Use existing duct via lube cart.


Cable Rejuvenation




Benefits:

+Minimal outage since new circuit is built in parallel with existing circuit



KEasements, HOA Approvals and Permits

KExpensive. Historically ~$800,000/mile

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Seema Abraham

Senior Project Manager

Reliability and Infrastructure Replacement

[email protected]

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Documents

SM SOUTHERN CALIFORNIA EDISON® Together, Making T&D the Safest Place to Work Cable-in-Conduit (CIC) Challenges and Strategies NameSeema Abraham TitleSenior