identifying solutions 101 overhead reliability to

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

2

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

3

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

4

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

7

8

EPRI Pole Strength testing

• Pole Strengths

– Class 2, southern

pine for mainline

– 4,000 lb strength

9

EPRI Component testing

10

EPRI Tie and pin insulator test

11

Pole top pin and insulator test

12

Post insulator testing and steel distribution tie

13

Post insulator test and aluminum preformed tie

14

Structure Loading

Mechanical Strength Coordination

• Texas Ice Storm

15

Structure Testing 2018

• Xcel Energy tangent structure 15kV

16

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

17

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

18

Structure Testing 2018

• Xcel Energy tangent structure 35kV

19

Structure Testing 2018

20

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

21

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

• Arm does twist to help release

Preformed Tie on Post Insulator Holding Strength

22

23

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.

24

• 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

25