Xcel Energy Storm Simulation in conjunction with EPRI Spring IEEE/PES July 2015 Dave Flaten and Betsy Coppock

Transcription

1 1 Xcel Energy Storm Simulation in conjunction with EPRI Spring 2014 IEEE/PES July 2015 Dave Flaten and Betsy Coppock

2 2 Line to Simulate Trees Falling 3 miles long, 70 structures, 200 foot spans #4 Copper phase wires, #2 ACSR neutral on 35 class 4 or 5 poles Cross arm construction, neutral low, center phase on pole top pin Estimated Age years Not a tree to fall on line

3 Test Test Description Complete 1 Old crossarm, old #4 Cu conductor Tue May 6, 9:37 2 New wood crossarm, old #4 Cu conductor Tue May 6, 11:26 3 Old crossarm, old #4 Cu conductor Tue May 6, 2:05 4 New fiberglass crossarm, old #4 Cu conductor Wed May 7, 9:05 5 New wood crossarm, old #4 Cu conductor, with tele-comm Skipped 6 Old crossarm, old #4 Cu conductor, with tele-comm Wed May 7, 10:48 7 New fiberglass crossarm, old #4 Cu conductor with tele-comm Wed May 7, 1:51 8 Old crossarm, new #2 ACSR conductor, hand tie Skipped 9 Old crossarm, new #2 ACSR conductor, preformed tie Thurs May 8, 9:15 10 New wood crossarm, new #2 ACSR conductor, hand tie Skipped 11 New wood crossarm, new #2 ACSR conductor, preformed tie Thurs May 8,11:25 12 New fiberglass crossarm, new #2 ACSR conductor, hand ties Skipped 13 New fiberglass crossarm, new #2 ACSR conductor, preformed ties Thurs May 8, 1:13 14 Old crossarm, old #2 ACSR conductor, old crossarm, hand ties Fri May 9, 12:32pm 15 Old crossarm, new 2/0 ACSR conductor, hand tie, old poles no down guys Fri May 9:26 am 16 New fiberglass crossarm, new 2/0 ACSR conductor, preformed ties, set new poles 40 class 3, old poles remained, installed down guys Fri May 10:29 am 3

4 4 12 Tests

5 5 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 (ground line, pole top and crossarm) may limit storm damage Telecommunication attachments did not alter results with #4Cu.

6 6 Cross-Arms New fiberglass cross-arms are strong and stiff, they transfer force to the next structure down

7 7 Cross-Arms Typically insulators and insulators ties were stronger than old cross-arms

8 8 Pins and Insulators Pole top pins with lag bolts fail more easily than cross-arm pins Hand ties didn t slip much

9 9 Damage Location and Timing Damage can occur several spans from initial tree impact location Much of the structure damage occurs on the rebound after the first break

10 10 Old System is Resilient Our existing system is resilient, small poles and cross-arms in good condition with small copper wire work well together A substantial tree is required to break wire

11 11 Previous Damage Previous mechanical or arcing damage provides a significant weak spot for wire and wood

12 Details of 3 simulations 12

13 Test 13 13

14 Test 13 New Fiberglass cross-arms, new #2 ACSR, preformed ties Wrecking Pole Pole 53 Pole 52 Pole 51 Pole 50 Pole 49 Pole 48 Pole 47 Dead-end Fiberglass arm Fiberglass arm Field side conductor snapped near pole Field side conductor broke; insulator landed 30 ft toward pole 51 Pole top pin pulled out; tie pulled out of insulator Some pole movement 2 in toward pole 51 Conductor remained in place between poles 48 and 49 Telecomm, pole, hardware and cross arm undamaged Dead end with fiberglass arm Pole top split considerably and cross arm fell to ground and brought part of pole top with it (about 7 ft); break was 1 ft from top of pole and about 6 ft long Center phase broken but hanging on by steel strand Cross arm pins split out field side Bent center pin toward pole 51 Neutral spool and bolt okay Pole undamaged Top of pole split Field side top of insulator sheared off Cross arm rotation counterclockwise 5 deg Arm brackets sunk into pole Mounting bolts bent, but undamaged Neutral bolt bent, no damage to spool Lag bolt pulled out of pole top pin but no damage to pin Cross arm, field side and road side insulators undamaged No pole or telecomm damage 0.5 in rotation clockwise at pole base 1 in movement toward pole 50 and 0.5 in toward pole 48 Hand ties Some movement about 1 in each way at pole base Pole top bent toward pole 49 Neutral spool and bolt undamaged Conductors did not slip Existing lightning damage from cross arm to neutral bolt No damage to guy wire Both field side and center conductor broke about 1 ft off pin towards pole 48 14

15 15 Test 13 Pole 50 Pole 52 Pole dropped between 50 & 51 Pole 51

16 16 Test 13 Ground has lots of give Pole 47 Pole 47 Pole 47 Pole 48

17 Test 2 17

18 Test 2 New wood cross-arms, old #4Cu Wrecking Pole Pole 11 Pole 10 Pole 9 Pole 8 Field side conductor ran away from break between 1.5 and 2 ft New wood cross-arm 45 deg clockwise at top New wood cross-arm No slip at conductors at tie Far anchor pulled at pole 8 drilled in too straight Minimal rotation; no damage 2 in clockwise rotation at base No damage to hardware or cross arm, or braces Pole top split, arm rotated counterclockwise 45 deg, pole top was not in good condition Hand tie for neutral connection broke No pole or other split At the same location on Test #1 that conductor broke 45 deg counterclockwise rotation of arm Base rotated 0.5 in (~2 deg) Roadside conductor ran toward test point by 2 ft Conductor pulled out Center phase pin is broke/bent New arm installed for test Neutral conductor damage existing, 2 Al strands broken, 4 Al strands and steel intact Neutral insulator hand tie broke; porcelain neutral spool broke Street side wire pulled >2 ft toward test point 2 in counterclockwise rotation at base Pole top split, had new arm after Test #1 #2 ACSR neutral pulled out of shoe One strand broken on neutral Base pulled 2 in toward strain 18

19 19 Test #2 Pole 8 Pole 10

20 Test 15 20

21 Test 15 21

22 Test 15 Old cross-arms, new 2/0 ACSR, hand ties, old poles, no down guys all 3 phases on cross-arms Wrecking Pole Pole 63 Pole 62 Pole 61 Pole 60 New wood cross-arm New wood cross-arm 1.5 inch movement at pole base toward pole inch movement at pole base toward pole inch movement at pole base in both directions 1.5 inch movement at pole base in both directions No rotation Cross arm split but field side insulator remained attached; no damage or movement in tie and conductor Some clockwise rotation of pole No rotation No damage Road side brace cracked No conductor axial movement, except maybe a bit on neutral No damage Neutral and hardware undamaged Field side pin pulled out of cross arm Cross arm split on field side 22

23 Pole 60 Pole 61 23

24 Going Forward with hardening In areas with trees - For all conductor sizes Replace poles with weathered/split pole tops Replace damaged arm and braces Replace obsolete construction (Lag bolts) Investigate different mounting options for fiberglass arms 24

25 Going Forward with hardening on old small wire (#4Cu) lines Beyond tree coverage but within run between dead-ends Consider expanding replacement of compromised structures 2-3 spans beyond tree coverage 25

26 Going Forward with hardening on #2 ACSR lines Beyond tree coverage but within run between dead-ends Reacts Similarly to #4Cu only more pole top strain Same criteria as old small wire but judge more critically Consider expanding replacement of compromised structures dead-end to dead-end 26

27 Going Forward with hardening on 2/0 ACSR and larger lines Beyond tree coverage but within run between dead-ends More Pole Top Strain, More Severe and Multiple Damage Sites Likely Pole needs to be stronger class or minimum top circumference Use new wood/fiberglass cross-arms Must upgrade entire line deadend to deadend 27

28 28 MORE TO LEARN