Identifying Solutions 101

Overhead Reliability to Resiliency

Betsy Coppock

10.10.19

Reliability to Resiliency

• Once you have a goal - Figure out the solution

• To find the solution, you need to figure out what’s the problem

• To figure out the problem you need to know what’s happening

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Reliability to Resiliency

• Goal - Xcel Energy wants a more resilient system

– Less damage in storms

– Easier and faster to repair

– Less hazards to the public

– Uniform and guided inspection

• Not much has changed since utilities began using wood poles and crossarms

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Finding the Problem - Testing with EPRI

• Did 13 tests

• Old line but almost all

poles sound at ground line

• Conductors

– Old #4 Cu solid

– Old and new #2 ACSR

– New 2/0 ACSR

• Crossarms

– Old existing wood

– Added new wood

– Added fiberglass

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Pole Failure

• Ground line pole failure difficult to achieve

• Top of pole failed frequently

• Pole top condition prior to test was a strong indicator if pole top would stay intact during test.

• Good inspection/ maintenance programs should limit storm damage

Crossarm Failure

• Typically insulators and insulators ties were stronger than old cross-arms

• Broke tops off some porcelain pin insulators

Conductor Size Impact

• Damage happens on impact but also on conductor breakage recoil

• Pole top damage common all conductors

• Old #4 Cu higher probability of conductor breakage

• New #2 ACSR conductor high probability of crossarm breakage

• New 2/0 ACSR broken pole at groundline

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EPRI Pole Strength testing

• Pole Strengths

– Class 2, southern

pine for mainline

– 4,000 lb strength

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EPRI Component testing

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EPRI Tie and pin insulator test

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Pole top pin and insulator test

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Post insulator testing and steel distribution tie

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Post insulator test and aluminum preformed tie

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Structure Loading

Mechanical Strength Coordination

• Texas Ice Storm

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Structure Testing 2018

• Xcel Energy tangent structure 15kV

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EPRI Structure Testing 2018

• Coordinated release – 15/25kV

– PUPI 2000 Tangent Arm

– 336 ACSR

– 4” x 4” washers

• Damage – 15/25kV

– Steel top ties came loose

– Bent arm pins

– Some arm bracket bending

– Possible insulator damage

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Preformed Tie on Pin Holding Strength

• Release

– Insulator rotates

– Pins bend

– Ties came loose

• Strength

– Arm pins bend easier than pole top pin

– Release at a lower strength

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Structure Testing 2018

• Xcel Energy tangent structure 35kV

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Structure Testing 2018

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Structure Testing 2018

• PUPI Arm Strength 6400lb vertical

– 336 ACSR, distribution tie, 4” x 4” washer above and below

• Three tests, same results – tried weaker tie and stronger arm

– Cantilever is too much

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• Insulator doesn’t rotate and insulator pin doesn’t bent

• Arm does twist to help release

Preformed Tie on Post Insulator Holding Strength

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Fiberglass arm testing

• 35kV Polymer Post

– 4” x 4” top and bottom

– 16” tall polymer post

– Maximum force – 961 lb

Structure Testing 2019

• Xcel Energy tangent structure 35kV

• Polymer clamp top insulators

– Force to slip around 1,000 lb.

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• Change in thinking about the Distribution System

• Automobile Industry

• Not selling 1950’s Chevy (Even if you like the styling)

• New models are better, more reliable, safer and efficient

• Utility Business

• Building 1900’s distribution isn’t going to take you further

• Inspect, maintain and replace exiting structures

• Build more resilient structures going forward

Conclusion

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