sm southern california edison® together, making t&d the safest place to work cable-in-conduit...
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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
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SOUTHERN CALIFORNIA EDISON®
Together, Making T&D the Safest Place to Work
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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SOUTHERN CALIFORNIA EDISON®
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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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SOUTHERN CALIFORNIA EDISON®
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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.
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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
Rigid duct via Directional Boring
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
Rigid duct via Directional Boring
Use existing duct via lube cartRigid duct
installed via trenching
Cable Rejuvenation
Rigid duct via Directional Boring
Selective replacement of only cable segments determined “bad” via PD testing
Rigid duct installed via trenching
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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.
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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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SOUTHERN CALIFORNIA EDISON®
Together, Making T&D the Safest Place to Work
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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
Rigid duct installed via trenching
Cable Rejuvenation
Rigid duct via Directional Boring
Selective replacement of cable segments determined “bad” via PD testing
Rigid duct installed via trenching
Benefits:
+Promises to extend cable life by up to 40 years
+All terminations are replaced
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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
Run to failure Rigid duct via Directional Boring
Use existing duct via lube cart
Rigid duct installed via trenching
Cable Rejuvenation
Rigid duct via Directional Boring
Selective replacement of cable segments determined “bad” via PD testing
Rigid duct installed via trenching
Benefits:
+Least expensive of all options (when it works)
+No need for easements
+New “Flat-Strap” cable should have a MTTF of 46 years
Issues / Challenges:
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
Run to failure Rigid duct via Directional Boring
Use existing duct via lube cart
Rigid duct installed via trenching
Cable Rejuvenation
Rigid duct via Directional Boring
Selective replacement of cable segments determined “bad” via PD testing
Rigid duct installed via trenching
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
Issues / Challenges:
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
Run to failure Rigid duct via Directional Boring
Use existing duct via lube cart.
Rigid duct installed via trenching
Cable Rejuvenation
Rigid duct via Directional Boring
Selective replacement of cable segments determined “bad” via PD testing
Rigid duct installed via trenching
Benefits:
+Minimal outage since new circuit is built in parallel with existing circuit
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Issues / Challenges:
KEasements, HOA Approvals and Permits
KExpensive. Historically ~$800,000/mile
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SOUTHERN CALIFORNIA EDISON®
Together, Making T&D the Safest Place to Work
Seema Abraham
Senior Project Manager
Reliability and Infrastructure Replacement
29
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