2015 IEEE REPC Engineering Analysis of Possible Effects of 2017 NESC Change Proposal To Modify or Remove 60’ Exemption April 20, 2015 Robert W. Harris, PE and Shawn M. Higbe, PE

Background Debate on validity of Rule 250B and 60’ Exclusion began nearly 20 years ago. After 2012 Code Cycle, some thought the issue settled. Hurricane Sandy breathed new life into the issue.

2017 NESC Code Cycle Change Proposals submitted first half of 2013. Subcommittees met Fall 2013. Two CPs submitted on these Rules: 250B Combined Ice & Wind District 250C Extreme Wind 250D Extreme Ice & Wind

NESC Change Proposals CP 4611 Proposed Elimination of: Rule 250B 60’ Exemption for Rule 250C 60’ Exemption for Rule 250D Unanimously Rejected by SC 5

NESC Change Proposals CP 4610 Originally Proposed: Rejected by SC 5 15.5 psf for Grade C 18 psf for Grade B Only if structure <= 60’ Only for Rule 250C Rule 250D? Rejected by SC 5

NESC Change Proposals CP 4610 (Modified) Proposed: Tie Vote! 15 psf regardless of Grade Only if structure <= 60’ Only for Rule 250C Eliminating 60’ Exclusion for Rule 250D Tie Vote!

NRECA’s Role Keep up with developments which affect our members. Inform our members. Seek guidance and support, if necessary, to determine further action. T&D Engineering Committee.

NRECA T&D Committee 74 Co-Op Engineers, RUS Representatives & Consultants. Six different Subcommittees. Overhead Lines Subcommittee Kevin Jordan is a member from Horry Electric Cooperative in Conway, South Carolina.

Why South Carolina?

Study Group Ten South Carolina Distribution Co-Ops Two North Carolina Distribution Co-Ops One Distribution Co-Op Each from Florida & Georgia Two G&T Co-Ops

Shawn M. Higbe, PE McCall-Thomas Engineering Co., Inc. Orangeburg, SC

Project Details Bid Proposal from McCall-Thomas Engineering Model recently built Distribution Lines. Analyze using SpidaCalc and Partner Staking. Evaluate modification and elimination of the 60’ Exclusion. Analyze effect of Joint Use Attachments.

Line Designs 1 - #2 ACSR 1 - #1/0 ACSR 3 - #336 ACSR 3 - #477 ACSR All built to Rule 250B- Medium Load District- Grade C

Rule 250C- Extreme Wind Extreme Wind at 15 psf Grade C Existing Grade B Extreme Wind at 15 psf Grade B Extreme wind at 18 psf Grade B Extreme Wind at 90 mph Extreme Wind at 130 mph

Additional Loading Joint Use One cooperative fiber, 1’ below neutral One telephone joint user One telephone and one cable joint user One cooperative fiber, one telephone and one cable joint user

Basic Design Data (As-Built for Rule 250B) Standard RUS 25 kV construction Southern Pine CCA Poles 40’ Class 5 for 1 - 2 ACSR 40’ Class 4 for 1 - 1/0 ACSR 40’ Class 4 for all 3 base cases 45’ Class 3 for 3 lines with taps 50’ Class 3 for 3 vertical construction 55’ Class 3 for 3 vertical construction with taps

Cost Analysis Pole Height Class and Cost Data Material and installation cost of poles only.

Grade C Analysis 1 - #2 ACSR - Power 19 Poles Case Description Change-Out Requirement Cost Increase Extreme Wind, 15 psf None NA Extreme Wind, 15.5 psf Extreme Wind, 90 mph Extreme Wind, 130 mph 2 poles 1.78%

Grade C Analysis 3 - #336 ACSR - Power 22 Poles Case Description Change-Out Requirement Cost Increase Extreme Wind, 15 psf None NA Extreme Wind, 15.5 psf 1 pole 0.17% Extreme Wind, 90 mph 4 poles 0.94% Extreme Wind, 130 mph 19 poles 14.15%

Grade C Analysis 1 - #1/0 ACSR - Power/JU 10 Poles Case Description Change-Out Requirement Cost Increase Extreme Wind, 15 psf – Power Only None NA Extreme Wind, 15.5 psf – Power Only Extreme Wind, 90 mph – Power Only Extreme Wind, 130 mph – Power Only 4 poles 8.17% Extreme Wind, 15 psf – Power/JU 0 / 1 / 2 / 4 0 / 0.38 / 1.2 / 3.42% Exreme Wind, 15.5 psf – Power/JU 0 / 1 / 3 / 4 0 / 0.38 / 1.58 / 3.42% Extreme Wind, 90 mph – Power/JU 2 / 2 / 4 / 5 0.98 / 1.39 / 3.42 / 10.98% Extreme Wind, 130 mph – Power/JU 6 / 7 / 9 / 9 20.42 / 25.27 / 40.8 / 58.69%

Grade C Analysis 3 - #477 ACSR - Power/JU 27 Poles Case Description Change-Out Requirement Cost Increase Extreme Wind, 15 psf – Power Only 1 pole 0.8% Extreme Wind, 15.5 psf – Power Only Extreme Wind, 90 mph – Power Only 3 poles 1.63% Extreme Wind, 130 mph – Power Only 23 poles 10.75% Extreme Wind, 15 psf – Power/JU 2 / 4 / 5 / 5 1.3 / 2.21 / 2.54 / 5.23% Exreme Wind, 15.5 psf – Power/JU 3 / 4 / 5 / 6 1.63 / 2.21 / 3.72 / 5.56% Extreme Wind, 90 mph – Power/JU 3 / 7 / 13 / 17 3.1 / 5.21 / 8.4 / 9.62% Extreme Wind, 130 mph – Power/JU 24 / 25 / 25 / 25 33.6 / 44.9 / 51.2 / 60.8%

Grade B Analysis 1 - #2 ACSR - Power 19 Poles Case Description Change-Out Requirement Cost Increase Medium B 2 poles 0.95% Extreme Wind, 15 psf None NA Extreme Wind, 18 psf

Grade B Analysis 3 - #336 ACSR - Power 22 Poles Case Description Change-Out Requirement Cost Increase Medium B 1 pole 2.27% Extreme Wind, 15 psf 0.16% Extreme Wind, 18 psf

Grade B Analysis 1 - #1/0 ACSR - Power/JU 10 Poles Case Description Change-Out Requirement Cost Increase Medium B – Power Only 1 pole 0.83% Extreme Wind, 15 psf – Power Only None NA Extreme Wind, 18 psf – Power Only Medium B – Power/JU 0 / 2 / 3 / 5 0 / 2.02 / 3.27 / 2.54% Exreme Wind, 15 psf – Power/JU 0 / 1 / 3 / 5 0 / 0 / 0 / 1.97% Extreme Wind, 18 psf – Power/JU 0 / 1 / 3 / 3 0 / 0 / 0 / 4.2%

Grade B Analysis 3 - #477 ACSR - Power/JU 27 Poles Case Description Change-Out Requirement Cost Increase Medium B – Power Only 2 poles 0.8% Extreme Wind, 15 psf – Power Only 1 pole 0.46% Extreme Wind, 18 psf – Power Only 3 poles 1.61% Medium B – Power/JU 3 / 2 / 5 / 14 2.66 / 0.67 / 1.47 / 4.14% Exreme Wind, 15 psf – Power/JU 2 / 4 / 3 / 6 1.39 / 2.19 / 3.81 / 4.7% Extreme Wind, 18 psf – Power/JU 5 / 5 / 5 / 6 3.23 / 4.02 / 4.82 / 7.16%

Conclusion Current Change Proposal- minimal cost increases, but increases design complexity for no apparent gains. 15.5 psf and 18 psf cause more significant cost increases. Elimination of 60’ Exclusion would bring major cost increases, especially in joint use situations.

VP, Director of Electrical Engineering Division Questions? Robert W. Harris, PE Principal, Transmission & Distribution Engineering Office 703-907-5753 Cell 571-205-3189 robert.harris@nreca.coop Shawn M. Higbe, PE VP, Director of Electrical Engineering Division www.McCall-Thomas.com Office 803-534-1040, ext. 1218 shigbe@mcteng.com