1. 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

2. 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.

3. 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

4. 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

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

6. 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!

7. 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.

8. 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.

9. Why South Carolina?

10. 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

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

12. 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.

13. 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

14. 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

15. 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

16. 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

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

18. 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%

19. 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%

20. 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 / / 40.8 / 58.69%

21. 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%

22. 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

23. 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

24. 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%

25. 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%

26. 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.

27. VP, Director of Electrical Engineering Division
Questions?
Robert W. Harris, PE Principal, Transmission & Distribution Engineering Office Cell
Shawn M. Higbe, PE
VP, Director of Electrical Engineering Division
Office , ext. 1218