Underground Secondary Cable & Connections

Timothy J. McLaughlin For ICC Educational Program

Spring 2005 St. Pete Beach, FL.

Presentation adapted from article

How Reliable Are Your Secondary UG Circuits?published in

Transmission & Distribution World magazine August 2003

PSE&G Facts

2,600 mile service area running diagonally across NJOver 2 million customersCombined electric and gas utilityPrimary voltages 4, 13, & 26 kVSecondary voltages 120/240 (radial),

120/208 (network), 277/480 (high-voltage network)

Realize there is a problemEvaluate the problems and associated costs

Search for a new technology?Evaluate possible solutionsAdapting new technologyField acceptanceResults of change

7- Step Program

Scope PSE&G installs approx. average 1.5 million ft

(457km) of secondary cable per year.Engineering and field crews started taking note of

the significant number of failures on secondary system.

Primary failures are tracked very closely where, why, how it was repaired etc.

In contrast, secondary failures are numerous and not tracked in any way

Secondary Cable

UG sizes - #4,#2,2/0,350,500,750All Copper! (Since 1980)XPLE insulation on smaller sizes EPR insulation with a Hypolon jacket on

larger sizes (replaces EPR and Neoprene) = better mechanical protection

Engineering Studies Secondary Failures

Study trouble crew work orders - 12 monthsInvestigation results

> 1800 failures per year on secondary> $1.5 million estimate in repair costsAverage $700 per repair

Large % of failures occurred at connectors.Failed connections sealed/insulated with

tape.

Digging Into Cause

Existing hand taping process Apply mastic sealing tape Apply rubber and vinyl tape

Quality of installation HIGHLY dependent on installerNo matter how well tape is applied it will

eventually leak and allow moisture in.

The Failure ProcessRoot Cause: Moisture Ingress Into

Connection

Leakage current accelerates corrosion reaction

Al + H2O Al2(OH)3 + H2Aluminum hydroxide + Hydrogen

Eventually, cables corrodes and has open failure.

Typical failure

Secondary Connection Failures

Salt water from rain and road salt corrode connector rapidlyMechanical connections come loose due to

water ingressImpossible to seal connection with tapingLarge solder-type connections are short

term (solder is a poor conductor and has a low temp. rating)

Results of inferior sealing

High Failure Rates Short Service Life Span High Restoration Costs Negative Customer Satisfaction

Search for New Technology

Requirements for a new solution Seals extremely well with long lifetime Easily repeatable installation regardless of

installer or conditions. Can install with insulated gloves on for hot

installs. Solutions must be available for the wide variety

of connections

Alternatives ConsideredHeat Shrink Tubes

Cold Shrink Tubes

Pre-molded rubber boots

Gel sealing products

Evaluation

Heat shrink, cold shrink, and pre-moldedAdvantages

Seals well Multiple cable ranges

Disadvantages

Must be placed on cable prior to connector installation Require additional installation space due to parking on cable Require larger excavation in direct buried application

Evaluation

Gels Provided wrap-around installation Seemed easier to install with consistent performance

and minimal training Products available for the wide variety of applications Allows for easy and clean re-entry

Gels met all of our requirements and were adapted on a trial basis.

The gel technologyWhat is Gel?

Gel: Polymer Network with Embedded Fluid

Silicone oil embedded in a cross-linked silicone matrix

Combines the advantages of solid and liquid insulating materials

9 Solid: Elastic memory9 Liquid: Wetting, conforms to surfaces

Unique tackiness and thermal long-termstability

Excellent aging properties

Extremely high elongation and elasticity

Excellent dielectric properties

How gel seals and prevents corrosionGel: Moisture displacement

Displacement of possible moisture Gel wets the surface applying a thin

layer of silicone oil Corrosion cannot occur without

water & oxygen in contact withmetal surface

Gel encapsulates connections

Dielectric strength 40kV/cm minimumGood chemical resistance UV Resistance Fungus resistant

Gel Properties

Field Acceptance of Gel

Critical factors for Fieldacceptance: Belief in product Makes their job easier,

not more difficult Product performs as promised

The gels were readily accepted by the crews and continue to be after more than 3 years of use.

500 & 350 KCMIL CU Bus

Compression connection core

Rubber insulatedTotally sealed

Service Bus

350 2/0(2), #2(2) 4/0 - #2(4)Multiple taps for

flexibilityTotally sealedConnects to main busEliminates the need

for vice-type connectors

Results

After several years, gel products continue to prove their value. No new installation failuresFailures are NOT occurring on the gel

products.New applications are still being introduced.

Gel ApplicationsCommon Industry Uses

URDMan Holes Street Light Bases (Gel-Cap)Taps

New Applications (PSE&G Leading)

500 and 750 MCM in-line limitersRe-Jacketing URD Primary CableGas Application Service Entrance Seal Sealing submersible elbow installations

Gas Application Service meter

Conclusion

We are still convinced going to gel technology is the right move.

We continue to increase the number of applications which we seal with gel.

We are already seeing real benefit in time savings and reliability.

Cost avoidance of repair work Full benefits will be realized in the future due to

reduced secondary failures and greater customer satisfaction.

Questions?

Comments?