NESC Subcommittee 2

1
NESC Subcommittee 2
IEEE
Ewell T. (Tim) Robeson Carolina Power Light
Co. July 19, 2001
2

NESC Grounding Methods

• Presentation Objectives
• Working Group 2.1 Report- Section 2 Definitions.
  Definitions for different types of grounded or
  ungrounded electric supply systems.
• Subcommittee 2- Section 9, Grounding Methods for
  Electric Supply and Communications Facilities,
  2002 NESC

3
NESC Working Group 2.1

• Established 1996 -Provide definitions of methods
  to ground electric supply systems.
• Proposed Definitions appear in the 2002 NESC
  Pre-print. Comment period resulted in some
  revision.

4
Grounding Definitions

• Section 2- New definitions related to system
  grounding.
• Multigrounded/multiple grounded system
• Neutral conductor
• Shield wire conductor
• Single grounded/unigrounded
• Ungrounded system

5
NESC Subcommittee 2

• Section 9 revisions
• Rule number system changed (Example- Rule 93. is
  now Rule 093.)
• Metallic (underline is an addition)
• Part (Strikethrough is a deletion)

6
Section 9 Revisions

• Rule 093AMetallic electrical equipment cases or
  the structural metal frame of a building or
  structure may serve as part of a grounding
  conductor to an acceptable grounding electrode.

7
Section 9 Revisions, Cont..

• Rule 093C4. EXCEPTION Arrester grounding
  conductors may be copper-clad or aluminum-clad
  steel wire having not less than 30 of the
  conductivity of solid copper or aluminum wire of
  the same diameter, respectively.

8
Section 9 Revisions, Cont..

• Rule 094B2b. Longer rods or multiple rods may be
  used to reduce the ground resistance. Spacing
  between multiple rods should be not less than 1.8
  m (6 ft)
• EXCEPTION Other dimensions or configurations may
  be used if their suitability is supported by a
  qualified engineering study

9
Section 9 Revisions, Cont..

• Rule 096C. Multi-grounded systems
• RECOMMENDATION This Rule may be applied to
  shield wire(s) used as lightning protection
  conductor(s), which is grounded at the source and
  that meets the multigrounding requirements of
  this Rule

10
Section 9 Revisions, Cont..

• Rule 097A. (Note 3 has moved to note 4 and a new
  note 3 is added)3. Shield wires of power
  circuits

11
Section 9 Revisions, Cont..

• 097B- The grounding conductors of either of the
  equipment classes detailed in Rules 97A1, and
  97A2, and 97A3 may be interconnected utilizing a
  single grounding bonding conductor, provided
• 2. The secondary neutral, or the grounded
  secondary phase conductor is common with or
  connected to primary neutral, or a shield
  wire...

12
Section 9 Revisions, Cont..

• Rule 097D. Ungrounded or Single-Grounded and
  Multi-Grounded Systems
• 1. Ungrounded or Single-Grounded SystemsWhere
  the secondary neutral is not interconnected with
  the primary surge-arrester grounding
• . The primary grounding conductor, or the
  secondary grounding conductor, shall be insulated
  for 600 V.

13
Section 9 Revisions, Cont..

• Rule 097G. Except where separation is required in
  Rule 97A, communication systems messengers are to
  be grounded on a joint use structure containing
  an electric supply grounding electrode conductor,
  the grounding system of the communication system
  should be bonded with the grounding electrode
  conductor of the electric supply system. Where
  the electric supply utility is maintaining
  isolation between primary and secondary neutrals,
  the communication system ground shall be
  connected to the primary ground conductor.

14
Section 9 Revisions, Cont..

• Rule 099C. Bonding of Electrodes
• A bond not smaller than AWG No. 6 copper or
  equivalent shall be placed between the
  communication grounding electrode and the supply
  system neutral grounding electrode where separate
  electrodes are used in or on the same building or
  on the same served structure.

15
Section 9 Revisions, Cont..
Rule 099C. Bonding of Electrodes, Cont.

• A bond not smaller than AWG No. 6 copper or
  equivalent shall be..served structure.
• RECOMMENDATION If water piping is used as a
  bonding means, care must be taken to assure that
  the metallic path is continuous between
  electrodes.
• Note See NEC Article 800-40(d) for
  corresponding NEC requirements.

16
?? Questions ??
IEEE
Thank you! Ewell T. (Tim) Robeson, PE Carolina
Power Light Co. July 19, 2001
17
Part 1. Electric Supply Stations
Rules for the Installation and Maintenance of
Electric Supply Stations and Equipment
Jack ChristofersenCeCe Thursday -- July 19, 2001
18
Section 10. Purpose and Scope

• The purpose of Part 1 is to provide practical
  safeguarding of persons performing installation,
  operation, or maintenance duties in electric
  supply stations.

19
Section 10. Purpose and Scope

• The scope covers the electric supply conductors,
  equipment and structural arrangements in electric
  supply stations, that are accessible only to
  qualified personnel including equipment employed
  primarily for the utilization of electric power
  used by the utility in the exercise of its
  function as a utility.

20
Section 11 Protective Arrangements in
Electric Supply Stations
21
110. General Requirements

• A1. Types of Enclosures
• Metal fences, when used to enclose
  electric supply stations having
  energized electric conductors or equipment,
  shall have a height not less than 7 ft overall
  and shall be grounded in accordance with
  Section 9.

22
110. General Requirements

• A1. Types of Enclosures
• a. Fence Fabric, 7 ft or more in height
• b. A Combination of 6 ft or more or fence
  fabric and utilizing 3 or more strands of
  barbed wire to achieve an overall height of the
  fence of not less than 7ft.

23
110. General Requirements

• A2. Safety Clearance Zone
• Fences or walls, when installed as barriers for
  unauthorized personnel, shall be located such
  that exposed live parts are outside the safety
  clearance zone as illustrated in Figure 110-1 and
  shown in Table 110-1.

24
110. General Requirements
Live parts must be outside of arc
7ft min.
R
Fence
R
5 ft
Fig 110-1
25
110. General Requirements
30

• B. Rooms and Spaces
• All rooms and spaces shall comply with the
  following requirements
• 1. Construction
• They shall be as much as practical
  noncombustible.
• NOTE This Rule is not intended to prevent wood
  poles from being used to support conductors or
  equipment in electric supply stations.

26
110. General Requirements
30

• B. Rooms and Spaces
• 2. Use
• They should be as much as practical free from
  combustible materials, dust, and fumes and shall
  not be used for manufacturing or for storage.
• EXCEPTION 1 Equipment or materials essential for
  maintenance of installed equipment may be stored
  if guarded from live parts as required by Rule 124

27
110. General Requirements
30

• B. Rooms and Spaces
• EXCEPTION 2 Materials related to station,
  transmission, or distribution construction and
  maintenance work may be stored in the station if
  located in an area separated from the station
  electric supply equipment by a fence meeting the
  requirements of Rule 110A.

28
110. General Requirements
30

• B. Rooms and Spaces
• EXCEPTION 3 Stored material related to station,
  transmission, and distribution construction and
  maintenance work in progress may be temporarily
  located in a storage space meeting all of the
  following requirements

29
110. General Requirements
30

• B. Rooms and Spaces
• (1) Guarded or separated from live parts as
  required by Rule 124
• (2) Station exits continue to meet the
  requirements of Rule 113
• (3) Station working space continues to meet the
  requirements of Rule 125
• (4) Access is limited to qualified personnel
• (5) The storage location and content is such that
  the risk of fire does not unreasonably jeopardize
  station operation.

30
Section 12
Installation and Maintenance of Equipment
31
120. General Requirements
A. All electric equipment shall be constructed,
installed, and maintained so as to safeguard
personnel as far as practical. B. The Rules of
this Section are applicable to both ac and dc
supply stations.
32
124. Guarding Live Parts
Live Part
GUARD ZONE AT RADIUS R, SEE COLUMN 4, TABLE
124-1
VERTICAL CLEARANCE SEE COLULMN 2
TABLE 124-1
HORIZONTAL CLEARANCE SEE COLUMN 3, TABLE 124-1
Fig 124-1
33
124. Guarding Live Parts
A. Types of Guards 3. Supplemental Barriers or
Guards Within Electric Supply Stations Railings
are not substitutes for complete guards. If the
vertical distance in Table 124-1 cannot be
obtained, railings or fences may be used.
Railings or fences, if used, shall be not less
than 1.07 m (3.5 ft) high and shall...
34
124. Guarding Live Parts
Table 124-1 Part DHigh Voltage Direct Current
(Based on Transient Overvoltage)
35
Section 15. Transformers and Regulators
36
150. Current-Transformer Secondary Circuits
Protection When Exceeding 600 Volts

• (Old Rule)
• Secondary circuits, when in a primary voltage
  area exceed 600 V should, except for short lead
  lengths at the terminals of the transformer, have
  the secondary wiring adequately protected by
  means of grounded conduit or by a grounded
  metallic covering. Current transformers shall
  have provision for shorting the secondary wiring.

37
150. Current-Transformer Secondary Circuits
Protection When Exceeding 600 Volts

• (New Rule)
• Secondary circuits, when in the vicinity of
  primary circuits exceeding 600 V should, except
  for short lead lengths at the terminals of the
  transformer, have the secondary wiring adequately
  protected by means of conduit covering or some
  other protection. Any metallic covering used
  shall be effectively grounded, giving appropriate
  consideration to circulating currents. Current
  transformers shall have provision for shorting
  the secondary winding.

38
Section 17. Circuit Breakers, Reclosers,
Switches, and Fuses
39
170. Arrangement
Circuit breakers, reclosers, switches, and fuses
shall be so installed as to be accessible only to
persons qualified for operation and
maintenance... Conspicuous markings (such as
numbers/ letters/ symbols) shall be provided on
each device and at any remote operating points so
as to facilitate identification by employees
authorized to operate the device. No device
identification shall be duplicated within the
same supply station.
40
National Electrical Safety Code
Whats New In 2002 Edition
Significant Changes to Section 23 - Clearances
Jerry Reding NESC Subcommittee 4 July 2001
41
Summary

• Introduce Each Rule Category in Section 23
• Describe Any Significant 2002 Changes
• Brief Reason for Each Change

42
Basis For Computing Clearances
43
Rule 230 - General

• No Significant Changes in 2002

44
Rule 231 - Structures and Other Objects

• Clearances of Supporting Structures From Other
  Objects

45
Rule 231A - Fire Hydrants

• Not less than 1.2 m (4 ft) ...
• Revised Rule
• Clearance changed to recommendation
• Exception aligned with previous clearance

46
Rule 231B1 - From Streets, Roads,...

• Where there are curbs
• Revised Rule
• Included anchor guys
• Defined redirectional curbs
• Defined paved or swale-type curbs and placed
  facilities behind such curbs

47
Rule 232 - Vertical Clearances

• Vertical Clearances of Wires, Conductors, Cables,
  and Equipment Above Ground, Roadway, Rail, or
  Water Surfaces

48
Rule 232B3 - Equipment Cases

• Clearance to Support Arms and Equipment Cases
• Revised to include Support Arms

49
Rule 232B4a - Street Area Lighting

• a. The vertical clearance of street and area
  lighting
• Revised
• Include vertical clearances of street light
  luminaries above ground.

50
Table 232-1, Footnote 13

• Where this construction crosses over or runs
  along alleys, not subject to truck traffic
• Revised
• Clarify for use in areas not subject to truck
  traffic.

51
Table 232-1, Footnote 26

• When designing a line to accommodate oversized
  vehicles, clearance values shall be increased by
  the difference between the known height of the
  oversized vehicle and 4.3 m (14 ft).
• New
• Clarify treatment of large vehicles.

52
Table 232-2 - Category 2a

• Add footnote 7 lessor clearances for grounded
  equipment cases to Category 2a Roads, Streets,
  and alleys
• Revised
• Allow reduced clearances for equipment if it does
  not overhang roadway.

53
Rule 233 - Different Structures

• Clearances Between Wires, Conductors, and Cables
  Carried on Different Supporting Structures

54
Rule 234 - Other Installations

• Clearances of Wires, Conductors, Cables, and
  Equipment From Buildings, Bridges, Rail Cars,
  Swimming Pools, and Other Installations

55
Rule 234C3a - Attached to Buildings

• Energized service drop conductors
• 1) For 0 to 750 V, Rules 230C or 230 D
• 2) For over 750V, Rule 230C1
• Revised
• Include service voltages over 750 volts.

56
Rule 234C3c - Attached to Buildings

• Wires or cables attached to and run along side
  the installation not less than 75 mm (3 in).
• Revised
• Calls out a specific value instead of referencing
  a table.

57
234C3d(1) - Attached to Buildings

• EXCEPTION 1 Where the voltage between
  conductors cable meets Rule 230C1
• Revised
• Include voltages and cables over 750 volts.

58
Rule 234F - Grain Bins

• All portions of grain bins In addition, the
  following clearances shall also apply
• a. A clearance not less than 5.5 m (18 ft)
• b. horizontal clearance not less than 4.6
  m (15 ft)

59
Rule 234F - Grain Bins (cont)

• Revised
• Clearances based on physical distances instead of
  voltage class.

60
Rule 235 - Same Supporting Structure

• Clearance for Wires, Conductors, or Cables
  Carried on the Same Supporting Structure

61
235C2b(1) - Between Line Conductors

• c) For purposes of this determination
• Adds new rule c) which has summer loading (i),
  winter loading (ii), and an exception for a
  single utility with equal cables.
• Revised
• Re-organized the rule for clarity under various
  loading conditions. Excludes cables of same type
  and single ownership.

62
Rule 235H - Communication Spacing

• Clearance and Spacing Between Communication
  Conductors, Cables, and Equipment
• New
• Adds guidance for placing communication equipment
  on structures.

63
Rule 235I - Communication Antennas

• Clearances in Any Direction From Supply Line
  Conductors to Communication Antennas in the
  Supply Space Attached to the Same Supporting
  Structure
• New
• Handle communication antennas located in the
  supply space, which is becoming a common practice.

64
Rule 236 - Climbing Space

• Climbing Space
• No Significant Changes in 2002

65
Rule 237 - Working Space

• Working Space
• No Significant Changes in 2002

66
Rule 238 - Communication Supply

• Vertical Clearances Between Certain Communication
  and Supply Facilities Located on the Same
  Structure
• No Significant Changes in 2002

67
Rule 239 - Other Facilities On Structure

• Clearances of Vertical and Lateral Facilities
  From Other Facilities and Surfaces on the Same
  Supporting Structure

68
Rule 239A6 - Guards Protection

• 6. Where guarding and protection are required by
  other Rules,
• New
• Clarifies such guards should completely enclose
  the cable to ensure their protection.

69
Table 239-1 - Footnote 5

• 5These clearances may be reduced to not more than
  25
• New
• Footnote added to Row 2 of Table. Provide same
  reduced clearances as conductors from guy
  insulators.

70
NESC 2002 Overhead Lines-Strength Loading
IEEE
Larry Slavin Telcordia Technologies, Inc. July
18, 2001
71
NESC 2002Strength Loading Review

• NESC 1997
• NESC 2002 (Resolved/Final)
• Comparison

72
NESC 1997Winter Storm

• Combined Ice and Wind Loading (Rule 250B)
• Heavy (0.5-in. radial ice, 40 mph wind, 0F)
• Medium (0.25-in. radial ice, 40 mph wind, 15F)
• Light (0-in. radial ice, 60 mph wind, 30F)

73
(No Transcript)
74
NESC 1997Summer Storm

• Extreme Wind (Structures gt60 ft Height) (Rule
  250C)
• 50 year recurrence (0.02 annual probability)
• Fastest-mile average speed
• Exposure C (open terrain)
• 33 ft. elevation

75
Extreme Wind Map Rule 250C
76
Conductor Loading

• Combined Ice and Wind, or Extreme Wind
• Vertical weight of bare conductor plus ice
• Horizontal force of wind on conductor plus ice
• Added constant to resultant (for tension, not
  sag)
• Corresponding temperature (0F, 15F, 30F 60F)

77
Conductor Loading
ice
wind force
conductor
weight
78
Loads on Line Supports

• Vertical Loads
• Dead weight of bare supports and conductors, ...
• Ice load on conductors and wires (not supports)
• Transverse Loads
• Wind force on bare structures (without ice)
• Wind force on ice-covered conductors and wires

79
Loads on Line Supports
Tension
Transverse
Vertical
TOP VIEW
Tension
Angle Pull
80
Loads on Line Supports

• Angles
• Unbalanced tension at corners
• Longitudinal Loads
• Unbalanced pulls
• Unequal spans
• Deadends
• ..
• Simultaneous Application of Loads

81
Strength Overload FactorsSupports (Structures,
Guys, )

• Load x Overload Factor ? Strength x Strength
  Reduction Factor
• Overload Factor (typ.) ? 1
• Strength Reduction Factor (typ.) ? 1
• e.g., 1.0 for 50 year extreme event loadings,
  or some components (conductors, )
• e.g., 1.0 for metal

82
Overload Factors

• Grade of Construction
• Grade B
• Grade C
• Combined Ice-Wind vs. Extreme Wind
• Loads
• Vertical
• Transverse Loads
• Longitudinal
• Materials
• Wood
• Metal

83
Strength (Reduction) Factors

• Grade of Construction
• Grade B
• Grade C
• ..
• Combined Ice-Wind vs. Extreme Wind
• Materials
• Wood
• Metal
• Concrete

84
Conductor/Messenger Tension

• Combined Ice-Wind (60 rated strength)
• Extreme Wind (80 rated strength)
• Criteria applied with Overload Factor 1.0
• Initial unloaded tension (60F) ? 35 rated
  strength
• Final unloaded tension (60F) ? 24 rated
  strength

85
Insulators

• Combined Ice and Wind
• Cantilever (40 rated strength)
• Compression (50 rated strength)
• Tension (50 rated strength)
• Criteria applied without overload factors
• Extreme Wind
• Proper allowance should be made

86
NESC 2002
Strength and Loading Requirements (Modifications)
87
Status of MajorChange Proposals

• Eliminate 60 ft. exemption for Extreme Wind (CP
  2151)
• Rejected (WG 5.8 to study for 2007)
• Introduce New Combined Ice and Wind Map as
  alternative to present Storm Loading Map, Rule
  250B (CP 2309)
• Rejected (map incomplete, premature, inaccurate?)

88
Status of MajorChange Proposals (Contd)

• New Materials Fiber-Reinforced Composite Poles
  (CP 2219, )
• Rejected (insufficient material data)
• Major Revision of Strength Loading Sections 25
  - 27 (CP 2372)
• Rejected (WG 5.2 to continue developing for 2007)

89
Status of MajorChange Proposals (Contd)

• Uniform Treatment of Wood, Metal, Concrete
  (Reinforced, Prestressed)
• Consistent Overload Factors (CP 2233)
• Accepted
• All structures without conductors subject
• to Extreme Wind (CP 2306)
• Accepted

90
Consistent Overload Factors(Wood, Metal,
Concrete)
91
Status of MajorChange Proposals (Contd)

• New Extreme Wind Map (CP 2363)
• Accepted
• New Calculation Procedure

92
New Extreme Wind Map Calculation Procedure

• ASCE 7-98 Extreme Wind Map
• 50 year recurrence (0.02 annual probability)
• Gusts (3-second average)
• Open terrain
• 33 ft. elevation
• Includes Gust Response Factors
• Height
• Span length

93
New Extreme Wind Map Calculation Procedure

• Retains 60 ft. Exemption (Distribution)

94
1997 Extreme Wind Map Rule 250C
95
New (2002) Extreme Wind Map(3 Second Gusts)
Nominal speed, 33 ft. above ground, Exposure C
96
New Extreme Wind Map Calculation Procedure

• NESC-1997
• load (lbs) 0.00256 (Vmph)2 x shape factor x
  projected area (ft2)
• where Vmph fastest-mile (Figure 250-2, 1997)
• NESC-2002
• load (lbs) 0.00256 (Vmph)2 x shape factor x
  projected area (ft2)
• x kz x GRF x I
• where Vmph 3-sec. gust (New Extreme Wind
  Map),
• kz velocity pressure exposure coefficient,
• GRF gust response factor, and
• I importance factor (1.0)

97
New Extreme Wind Map Calculation Procedure
(Contd)

• Structure kz 2.01 x (0.67h/900)(2/9.5), 60 ft
  ? h ? 900 ft
• where h height structure (ft)
• Wire kz 2.01 x (h/900)(2/9.5), 33 ft ? h
  ? 900 ft
• where h height attachment point (ft)
• minimum kz 0.85

98
New Extreme Wind Map Calculation Procedure
(Contd)

• Structure GRF 1 2.7Es(Bs)0.5/kv2
• Wire GRF 1 2.7Ew(Bw)0.5/kv2
• where
• Es 0.346 x 33/(0.67h)1/7
• Ew 0.346 x 33/h1/7
• Bs 1/1 0.375h/220
• Bw 1/1 0.8L/220
• kv 1.43
• L Design Wind Span (ft)

99
New Extreme Wind Map Calculation Procedure
(Contd)
Gust Response Factor, GRF Tabulated Values
(Structure and Wire)

100
NESC
NESC 2002 vs. NESC 1997 (Comparison)
101
NESC 2002 vs. NESC 1997 Comparison

• Reduced Overload Factor for Metal,
  Prestressed-Concrete
• Rule 250B (Combined Ice Wind)
• Transverse wind
• Grade C (not crossing)
• 1.75 vs. previous 2.20
• Affects distribution and transmission
• Extreme Wind Loading (Rule 250C)
• 3-sec. gust map calculation procedure
• Affects transmission design only (gt60 ft.)

102
NESC 2002 vs. NESC 1997 Comparison (Contd)

• Distribution Lines (Combined Ice-Wind)
• Wood, Reinforced-Concrete
• no change
• Metal, Prestressed-Concrete
• reduced design load (transverse, Grade C, )

103
NESC 2002 vs. NESC 1997 Comparison (Contd)

• Transmission Lines
• Wood, Reinforced-Concrete
• no change in Combined Ice/Wind design loads
• new Extreme Wind design loads
• Metal, Prestressed-Concrete
• reduced Combined Ice/Wind design loads
  (transverse, Grade C, ) -- 0.80 factor
• new Extreme Wind design loads

104
Transmission LinesStructures - Combined Ice
Wind
Transverse Wind Load
105
Transmission LinesStructures - Extreme Wind
Transverse Wind Load
106
Transmission LinesStructures - Extreme Wind
Transverse Wind Load
107
Transmission LinesConductors - Combined Ice
Wind
Transverse Wind Load
108
Transmission Lines Conductors - Extreme Wind
Transverse Wind Load
109
Transmission LinesConductors

• Examples
• (Transverse Wind Load)

Woo
110
Transmission Lines - ExamplesStorm Loadings
Selected
111
Transmission LinesConductors

• Heavy Storm District
• (Wood)

Woo
112
Wood Transmission Heavy Storm Area, Grade B,
250 x 500
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
113
Wood Transmission Heavy Storm Area, Grade B,
100 x 2000
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
114
Wood Transmission Heavy Storm Area, Grade B, 50
x 2000
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
115
Wood Transmission Heavy Storm Area, Grade C,
250 x 500
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
116
Wood Transmission Heavy Storm Area, Grade C,
100 x 2000
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
117
Wood Transmission Heavy Storm Area, Grade C, 50
x 2000
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
118
Transmission LinesConductors

• Heavy Storm District
• (Steel)

Woo
119
Steel Transmission Heavy Storm Area, Grade B,
250 x 500
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
120
Steel Transmission Heavy Storm Area, Grade B,
100 x 2000
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
121
Steel Transmission Heavy Storm Area, Grade B,
50 x 2000
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
122
Steel Transmission Heavy Storm Area, Grade C,
250 x 500
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
123
Steel Transmission Heavy Storm Area, Grade C,
100 x 2000
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
124
Steel Transmission Heavy Storm Area, Grade C,
50 x 2000
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
125
Transmission LinesConductors

• Medium Storm District
• (Wood)

Woo
126
Wood Transmission Medium Storm Area, Grade B,
250 x 500
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
127
Wood Transmission Medium Storm Area, Grade B,
100 x 2000
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
128
Wood Transmission Medium Storm Area, Grade C,
250 x 500
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
129
Wood Transmission Medium Storm Area, Grade C,
100x2000
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
130
Transmission LinesConductors

• Medium Storm District
• (Steel)

Woo
131
Steel Transmission Medium Storm Area, Grade B,
250 x 500
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
132
Steel Transmission Medium Storm Area, Grade B,
100x2000
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
133
Steel Transmission Medium Storm Area, Grade C,
250 x 500
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
134
Steel Transmission Medium Storm Area, Grade C,
100x2000
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
135
Transmission LinesConductors

• Light Storm District
• (Wood)

Woo
136
Wood Transmission Light Storm Area, Grade B,
250 x 500
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
137
Wood Transmission Light Storm Area, Grade B,
100 x 2000
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
138
Wood Transmission Light Storm Area, Grade C,
250 x 500
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
139
Wood Transmission Light Storm Area, Grade C,
100 x 2000
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
140
Transmission LinesConductors

• Light Storm District
• (Steel)

Woo
141
Steel Transmission Light Storm Area, Grade B,
250 x 500
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
142
Steel Transmission Light Storm Area, Grade B,
100 x 2000
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
143
Steel Transmission Light Storm Area, Grade C,
250 x 500
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
144
Steel Transmission Light Storm Area, Grade C,
100 x 2000
250B (ice wind) -1997
250B (ice wind) -2002
250C (extreme wind) -1997
250C (extreme wind) -2002
145
NESC
NESC 2002 vs. NESC 1997 (Conclusions)
146
NESC 2002 vs. NESC 1997 Conclusions

• Distribution Design Loads
• Wood ? Same
• Reinforced-concrete ? Same
• Metal (Grade C) ? Reduced in Grade C
• Prestressed-concrete (Grade C) ?Reduced
  in Grade C

147
NESC 2002 vs. NESC 1997 Conclusions

• Transmission design loads depend upon combination
  of parameters
• - geographic area
• - grade of construction
• - material
• - conductor diameter
• - attachment height
• - span length

148
NESC
NESC 2007 (?) Integrated Re-Write of Strength
Loading
149
Integrated Re-Write of Strength Loading

• Based upon CP 2372 (Rejected for NESC-2002)
• Sags and Clearances also impacted
• Modified version proposed for NESC-2007 Edition
• To be available on NESC website (when?)
• Response form provided for reporting results of
  application to actual cases!

150
Integrated Re-Write of Strength Loading

• New Extreme Wind Map and wind pressure
  calculation procedure
• (Rule 250C, NESC-2002)
• Upgraded ASCE 7-98 Combined Ice and Wind Map
• Replaces Fig.250-1 Loading Districts
• Construction and Maintenance Loads

151
Integrated Re-Write of Strength Loading

• All loads apply to all structures independent of
  height, but ...
• Possible wind reduction if urban/suburban and ?
  60 ft. (Ref Working Group 5.8)
• Ice thickness reduction for Grade C
• Velocity pressure exposure coefficient kz and
  gust response factor GRF (functions of height and
  span length) applied to wind pressure for both
  storm loads

152
Integrated Re-Write of Strength Loading

• Consistent Overload and Strength Factors
• Alternative (Option) to Present (NESC-2002)
  Method ?

153
Integrated Re-write of Strength Loading (Contd)

• Results from actual applications (as reported on
  response forms) will be considered in developing
  final proposal for 2007 Edition

154
WHATS NEW IN 2002?
NESC SUBCOMMITTEE 7

• NESC Significant Changes
• Underground Lines

O. Chuck Amrhyn NESC Chairman July 19, 2001
155
(No Transcript)
156
RANDOM SEPARATION
157
RANDOM SEPARATION
158
RARANDOM SEPARATION
159
RANDOM SEPARATION
160
IDENTIFICATION MARKING BURIED CABLE
161
New NESC Rule 323C5

• 5. Any manhole greater than 1.25 m (4 ft) in
  depth shall be designed so it can be entered by
  means of a ladder or other suitable climbing
  device. Equipment, cables and hangers are not
  suitable climbing devices.
• Reason This rule was added because it was not
  adequately covered in the code.

162
New NESC Rule 350H

• H. The rules in this section also apply to direct
  buried supply and communications cables installed
  in duct that is not part of a conduit system.
• (the section referenced above is section 35,
  rules for direct buried cables)
• Also a NOTE will be added at the beginning of
  section 32
• (Underground Conduit Systems) thusly

163
New NESC Rule 350H (cont.)

• For cables installed in a single duct not part
  of a conduit system, the rules in section 35
  apply.
• Reason This rule was added to clarify the
  intent of the code that the direct buried
  cable rules in Section 35 apply to direct
  buried cable in duct that is not part of
  conduit system.

164
Revised NESC Rule 351A1

• 351A1 Cables should be located so as to be
  subject to the least disturbance practical. When
  cables are Cables to be installed parallel to
  other subsurface structures, but if this is not
  practical, the rules on separation in Rule 352
  353 or 354 shall should be followed.

165
Revised NESC Rule 351A1 (cont.)
Reason This rule was revised to allow joint
use trench without qualifications as to the
practicality of it. Joint trench has become
an accepted normal practice, and if the
appropriate rules are followed, it is a safe
practice.
166
Revised NESC Rule 352 and 354

• Presently the separation rules require a 12
  separation between supply cables and other
  underground structures, including gas and other
  fuel lines. If this is not practical, or
  conditions do not permit it, then a separation of
  less than 12 (random lay) is OK, provided all
  parties affected are in agreement and the random
  lay rules are followed.

167
Revised NESC Rule 352 and 354(cont.)

• The revised rules on separation will be two
  distinct rules
• (1) Revised Rule 353 for deliberate
  separation (Equal to or Greater Than 12),
  And
• (2) Revised Rule 354 for random separation (Less
  Than 12).

168
The most significant change is new NESC Rule
354A2 which states

• 354A2. Radical separation of supply and
  communication cables or conductors from steam
  lines, gas and other fuel lines shall be not
  less than 12 inches and shall meet Rule 353.
• The present rules do not allow a supply cable and
  gas line to have a separation of less than 12
  provided all the affected parties agree, but the
  new Rule 354A2, as stated above, will not allow a
  radical separation less than 12, even if the
  parties agree to it, or if they are owned by the
  same utility. The 2002 edition will have no
  exceptions.

169
Reason This rule was added because of the
concerns between supply and communica-tion
cables and gas lines as to adequate separation.
New Rule 354A2 (cont.)
170
Revised NESC Rule 353D1, Table 353-1, Exception

• Exception Where conflicts with other underground
  facilities exist, street light cables operating
  at not more than 150 volts to ground may be
  buried at a depth not less than 450 mm (18 in).
• Reason This rule was revised because the
  original intent was to allow a lessor depth only
  where other underground structures existed. The
  burial depth should correlate with voltage, not
  the type of system being installed.

171
New NESC Rule 380D

• D. Padmounted equipment, pedestals and
  otherabove ground enclosures should be
  located not less than1.2 m (4 ft) from
  firehydrants.
• ExceptionWhere conditions do not permit a
  clearance of 1.2 m (4ft), a clearance of not less
  than 900 mm (3 ft) is allowed.
• Reason This rule was added because padmounted
  equipment creates the same problems for firemen,
  as do overhead structures. It will also now be
  consistent with the overhead clearance section.

172
Revised NESC Rule 381G1

• 381G1. Padmounted and other above ground
  equipment shall have an enclosure that is either
  locked or otherwise secured against unauthorized
  entry.
• Reason This rule was revised so that
  non-padmounted equipment, such as secondary
  pedestals are included.

173
NESC Subcommittee 8
PART 4 RULES FOR THE OPERATION OF ELECTRIC SUPPLY
AND COMMUNICATION LINES AND EQUIPMENT
Jim Tomaseski International Brotherhood of
Electrical Workers July 18, 2001
174
NESC Subcommittee 8Work Rules

• PURPOSE IS TO PROVIDE
• PRACTICAL WORK RULES

175
NESC Subcommittee 8Work Rules

• HARMONIZED WITH
• OSHA FINAL RULES
• 1910.137 1910.269

176
NESC Subcommittee 8Work Rules

• RULE 410A2 - TRAINING
• DEMONSTRATED PROFICIENCY
• NESC AND OTHER RULES

177
NESC Subcommittee 8Work Rules

• RULE 411D
• SIGNS AND TAGS
• WARNING SIGNS ? EMPLOYEE SAFETY

178
NESC Subcommittee 8Work Rules

• RULE 423C4
• AIR SPACE OR BARRIER
• WITH TORCH OR FLAME NEAR
• EXPOSED GAS OR FUEL LINE

179
NESC Subcommittee 8Work Rules

• RULE 423D5
• SHORING PROVISIONS

180
NESC Subcommittee 8Work Rules

• RULES 431A1 431A2
• JOINT USE
• COMMUNICATIONS SUPPLY
• ENERGIZED UNTIL DE-ENERGIZED
• AND GROUNDED

181
NESC Subcommittee 8Work Rules

• RULE 431B
• ALTITUDE CORRECTION FACTORS
• MINIMUM APPROACH DISTANCES CORRECTED FOR
  COMMUNICATION WORKERS

182
NESC Subcommittee 8Work Rules

• TABLE 431
• APPROACH DISTANCE
• ?
• DISTANCE TO EMPLOYER
• (MATCH 441 TABLES)

183
NESC Subcommittee 8Work Rules

• RULE 441A
• DEFINITION OF
• DE-ENERGIZED

184
NESC Subcommittee 8Work Rules

• RULE 441A
• TWO TERMS
• DE-ENERGIZED
• DE-ENERGIZED AND GROUNDED

185
NESC Subcommittee 8Work Rules

• RULE 441A3b c
• AND
• TABLE 441-6
• MAXIMUM USE VOLTAGE

186
NESC Subcommittee 8Work Rules

• RULE 441A4a
• TRANSIENT OVERVOLTAGE CONTROL
• VOLTAGES ABOVE 72.5kV

187
NESC Subcommittee 8Work Rules

• RULE 441A5a b
• ALTITUDE CORRECTION CALCULATION
• CLARIFICATION ONLY

188
NESC Subcommittee 8Work Rules

• RULE 441B4a, b c
• SPECIAL RULES FOR WORKING ON INSULATOR ASSEMBLIES
  OVER 72.5kV
• 3 INSULATORS SHORTED

189
NESC Subcommittee 8Work Rules

• NEW RULE 447
• MOVED FROM RULE 276
• MORE APPROPRIATE IN PART 4