NESC Subcommittee 5 Changes to the 2017 NESC. Joseph Rempe 18 October 2016

Transcription

1 NESC Subcommittee 5 Changes to the 2017 NESC Joseph Rempe 18 October 2016

2 Re-format Rule 241.C. At Crossings 241. Application of grades of construction to different situations 2012 version 2

3 Re-format Rule 241.C. At Crossings 241. Application of grades of construction to different situations 2012 version 2017 version 3

4 Re-format Rule 241.C. At Crossings 241. Application of grades of construction to different situations 2012 version 2017 version Same Words Easier to Comprehend 4

5 Grade N CP Intention: Change Grade N Emergency & Temp Eliminate Grade N from Table

6 Grade N CP Intention: Change Grade N Emergency & Temp Eliminate Grade N from Table Final Modification: Keep Grade N Add NOTE to Rule 240.A. General: NOTE: For emergency or temporary installations, see Rule

7 Grade Cx CP Intention: Make Grade C at crossings an official Grade: Call it Cx List in Section 24-Grades of Construction 7

8 Grade Cx CP Intention: Make Grade C at crossings an official Grade: Call it Cx Potential Modification: List in Section 24-Grades of Construction Eliminate Grade C at crossings 8

9 Grade Cx CP Intention: Make Grade C at crossings an official Grade: Call it Cx Potential Modification: Final Action: List in Section 24-Grades of Construction Eliminate Grade C at crossings Reject any change 9

10 Revise Table Grades of Construction Applications 10

11 Revise Table Grades of Construction Applications CP Intention: Improve logical layout and format Columns sequence from low to high voltage Rows sequence from low to high voltage 11

12 2012 Table

13 2012 Table

14 2017 Table

15 2017 Table

16 Revise Table Grades of Construction Applications CP Intention: Improve logical layout and format Columns sequence from low to high voltage Rows sequence from low to high voltage FN 3 reversed; higher grade in the table 3 Grade B C construction shall may be used if the supply circuits will not be promptly de-energized, both initially and following subsequent breaker operations, in the event of a contact with lower supply conductors or other grounded objects. 16

17 Revise Table Grades of Construction Applications CP Intention: Improve logical layout and format Columns sequence from low to high voltage Rows sequence from low to high voltage FN 3 reversed; higher grade in the table Add FN 11 Grade N for dielectric fiber-optic supply cables 17

18 Revise Table Grades of Construction Applications CP Intention: Improve logical layout and format Meet Rule 230F1b Insulated Comm Cables in Supply Space Columns sequence and from low to high voltage Rows sequence from low to high voltage Supported by effectively grounded messenger FN 3 reversed; higher grade in the table or Add FN 11 Grade N for dielectric fiber-optic supply cables Bonded at intervals specified in Rule 092C to Supply messengers supporting cable meeting Rule 230C1 18

19 Revise Table Grades of Construction Applications Final Action: Accept CP Intention: Improve logical layout and format Columns sequence from low to high voltage Rows sequence from low to high voltage FN 3 reversed; higher grade in the table Add FN 11 Grade N for dielectric fiber-optic supply cables 19

20 k-factor Introduced in 1941 District Loads were reduced Clearances based on previous higher loads K-factor approximated the same resultant loading on the wire to create the same sags Clearances based on sags, not tension Resulting increase in tension not intended for structural design 2007 NESC added District Load Map to Sec 23 20

21 k-factor CP Intention: Set k=0 in section 25 Only affects guyed structures If tensions set at % limit, design tensions increase - everyday tensions increase Affect on structures considered small 21

22 k-factor CP Intention: Set k=0 in section 25 Only affects guyed structures If tensions set at % limit, design tensions increase - everyday tensions increase Affect on structures considered small Final Action: Reject Will coordinate effort with SC 4 in next cycle 22

23 Delete Rule 243.C.4 23

24 Delete Rule 243.C.4 When communication conductors are required to meet Grade B or C, only the requirements for mechanical strength for these grades are required. 24

25 Delete Rule 243.C.4 25

26 Delete Rule 243.C.4 Two new grades of construction: Undefined Loads + Grade B Strength Undefined Loads + Grade C Strength 26

27 Delete Rule 243.C.4 Final Action: Accept 27

28 Rule 250C: Add Wind Return Period 28

29 Rule 250C: Add Wind Return Period NOTE: The commentary to ASCE indicates that these wind speeds represent a 50-to-90 year mean recurrence interval. 29

30 Rule 250C: Add Wind Return Period NOTE: The commentary to ASCE indicates that these wind speeds represent a 50-to-90 year mean recurrence interval. Final Action: Accept 30

31 Rule 250C: Eliminate 60 ft Exclusion 31

32 Rule 250C: Eliminate 60 ft Exclusion Forgeeht about it!!!! 32

33 Non-linear analysis CP Intention: Rule 250B Grade B Increase Strength Factor when use non-linear Rule 250B Grade C Decrease Strength Factor when use linear Rule 250C&D.75 to.79 33

34 Non-linear analysis 34

35 Non-linear analysis Intention: Rule 250B Grade B Increase Strength Factor when use non-linear Rule 250B Grade C Rule 250C&D.75 to.79 Decrease Strength Factor when use linear As Modified in 2013: Rule 250B Rule 250C&D Reduce LF for non-linear Increase LF for linear 35

36 Non-linear analysis 36

37 Non-linear analysis 37

38 Non-linear analysis Further analysis showed inconsistencies in the results of applying these values. -Some of Grade C requirements higher than Grade B -Reduced requirements exceed increased due to non-linear load 38

39 Non-linear analysis Further analysis showed inconsistencies in the results of applying these values. -Some of Grade C requirements higher than Grade B -Reduced requirements exceed increased due to non-linear load Final Action: Reject 39

40 Clarification Determining Gust Response Factor 40

41 Clarification Determining Gust Response Factor Clarifies using span length to determine GRF Previously stated as design wind span Final Action: Accept 41

42 Clarify when ice is applied Rule 250D 42

43 Clarify when ice is applied Rule 250D Add ice to: Wires Conductors Cables Messengers Do not add ice to: Structure Other supported facilities 43

44 Clarify when ice is applied Rule 250D Final Action: Accept Add ice to: Wires Conductors Cables Messengers Do not add ice to: Structure Other supported facilities 44

45 New ASCE Reference Extreme Wind Map Figures

46 New ASCE Reference Extreme Wind Map Figures NESC ASCE 7-05 Minimum Design Loads for Buildings and Other Structures 2017 NESC ASCE Guidelines for Electrical Transmission Line Structural Loading 46

47 New ASCE Reference Extreme Wind Map Figures NESC Final Action: Accept ASCE 7-05 Minimum Design Loads for Buildings and Other Structures 2017 NESC ASCE Guidelines for Electrical Transmission Line Structural Loading Same Map Newly revised ASCE standard 47

48 New ASCE Reference Extreme Ice Map Figures

49 New ASCE Reference Extreme Ice Map Figures NESC ASCE 7-05 Minimum Design Loads for Buildings and Other Structures 2017 NESC ASCE 7-10 Minimum Design Loads for Buildings and Other Structures 49

50 New ASCE Reference Extreme Ice Map Figures NESC Final Action: Accept ASCE 7-05 Minimum Design Loads for Buildings and Other Structures 2017 NESC ASCE 7-10 Minimum Design Loads for Buildings and Other Structures Same Map New Edition of ASCE 7 50

51 Longitudinal Capability Rule 252.C.6 51

52 Longitudinal Capability Rule 252.C.6 It is recommended that structures having a longitudinal strength capability be provided at reasonable intervals along the line. 52

53 Longitudinal Capability Rule 252.C.6 Final Action: Accept Longitudinal capability recommendation moved the issue to a RECOMMENDATION 53

54 Aeolian Vibration Rule 261H.1.b 54

55 Aeolian Vibration Rule 261H.1.b 55

56 Aeolian Vibration Rule 261H.1.b Final Action: Accept 56

57 Aeolian Vibration Rule 261H.1.b Final Action: Accept 57

58 Insulators New Rating System Old Line Post ratings: Rating equal to average Lowest no less than 85% of average New Line Post ratings: Rating = Minimum of all insulators 58

59 Insulators New Rating System Old Transmission Suspension ratings: 1.2 standard deviations New Transmission Suspension ratings: 3.0 standard deviations 59

60 Exception Added Insulator Factory Tests Rule

61 Exception Added Insulator Factory Tests Rule 274 EXCEPTION: Guy insulators manufactured per designs for which validation tests have been performed and a valid quality assurance program is followed, this rule does not require that dry and wet flashover tests be performed on each guy insulator unit. 61

62 Insulators CP Intention: Introduce Load factors (LRFD) Adjust allowable stresses Mostly equivalent insulator applications Introduce Classes: Distribution & Trans Different allowables for Rule 250B vs 250C, D 62

63 Insulators: Table Load Factors 63

64 Insulators: Table Load Factors 64

65 Insulators Table

66 Insulators Table

67 Insulators Table

68 Insulators Table

69 Nonceramic Table cont d 69

70 Table cont d 70

71 Table cont d 71

72 Table cont d 72

73 Table cont d Final Action: Accept FN 3: This percentage shall be supplied by the manufacturer. 73

74 Subcommittee 5 Works in Progress 74

75 Subcommittee 5 Works in Progress Standardize Terminology Improve Clarity and Consistency K-factor 60 ft exclusion Non-linear Analysis Grade N Grade Cx 75

76 Subcommittee 5 Works in Progress Start Working Group Meetings in

77 IEEE WG-7 Changes to the 2017 NESC presented by Nelson Bingel

78 Add Temperature Map Figures For Rule 250D 78

79 Add Temperature Map Figures For Rule 250D To Be Used With 250D Extreme Ice & Concurrent Wind Final Action: Accept 79