Transcript Slide 0

CHANGES TO THE
2007 NATIONAL ELECTRICAL
SAFETY CODE
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Section 2, Definitions
• Supporting Structure Definition:
– Relocates and revises the definition of “readily
climbable supporting structure.”
– Combines “readily climbable” and “not readily
climbable” under one definition.
– Adds the notes that clarify what structures are
considered not “readily climbable” to the code.
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Rule 013C, Inspection and
Work Rules
• Inspection rules and work rules in the
current edition of the NESC shall apply to
inspection of or work on all new and
existing installations.
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Rule 018, Method of Calculation
• Where calculations are required, the resultant value
shall be rounded off to the nearest significant digit
unless otherwise specified by the applicable rule(s).
• Eliminates questions about whether such language as
“shall be not less than” requires rounding up or
rounding off.
• Note: Rule 230A4 requires clearance calculations to
be rounded up to match the decimal system used in
the rule or table.
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Rule 94B7, Directly Embedded
Metal Poles
• Allows directly embedded metal poles to be an
acceptable grounding electrode if:
• backfill is native backfill, concrete or conductive
grout,
• embedment is > 5’,
• metal thickness is > ¼”, and
• any protective coating is conductive.
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Rule 97G, Bonding of
Communication Systems to
Electric Supply Systems
• Requires using a common grounding conductor
or bonding separate grounding conductors
where both electric supply systems and
communications systems are grounded on a
joint use pole (except where separation is
required by Rule 97A).
• Use to be a “should” rule.
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Rule 215C, Grounding of
Circuits, Supporting Structures and
Equipment. Non-Current-Carrying Parts.
• Rules 215 C3- C6 new.
• Moved the guy insulator requirements of Rule 279 to Rule 215.
• All requirements for using guy insulators in lieu of grounding
guys will be in one place.
• Specific requirements for using insulators in lieu of grounding
guys and span wires are added.
• Rule 279 retains the strength requirements for guy insulators.
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Rule 217A1a,Supporting
Structures, Protection of
Structures, Mechanical Damage
• Moves the following from Note status to Rule
status:
“This rule does not require protection or
marking of structural components located
outside of the traveled ways of roadways or
established parking areas.”
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Section 23, General Clarification
for Neutral Clearances
• Revises Rules and Tables to clearly indicate supply
Rule 230E1 neutrals have different clearances from
supply conductors 0-750 V.
• Previously, some tables had separate categories for
230E1 neutrals and others included them within the
0-750 V category.
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Rule 230B, Ice and Wind
Loading for Clearances
• Retains the ice loading districts for determining
clearances.
• Retains General Loading Map (Figure 230-1) and Ice,
Wind and Temperature information (Tables 230-1 &
230-2) for clearances and inelastic deformation.
• Changes “loading districts” to “loading zones.”
• Appendix B created to explain.
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Table 232-2, Vertical Clearance of
Equipment Cases, Support Arms, Platforms,
Braces and URLP Above Ground, Roadway,
Rail or Water Surfaces
• Adds switch handles, platforms and braces to
the 1st column.
• Old FN1 is new FN6 and applied to category 1b
(Driveways, Parking Lots and Alleys), column 2
(UGLP 0- 750V).
• Old FN1b in new FN1 applied to category 1d
(Spaces and Ways Subjected to Pedestrians…),
column 2.
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Rule 234C3d(1), Clearances of
Wires, Conductors, Cables &
RLP from Buildings, Signs, Billboards,
Chimneys, Radio and TV Antennas
Tanks, etc.
• Increased the clearance of service drop
conductors over a roof (where not attached) from 8
feet to 10 feet.
• Combined Exceptions 1 & 2 into one exception
and rewrote for readability.
• Retains the reductions formerly allowed in
Exception 2.
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Rule 235G, Conductor Spacing:
Vertical Racks or Separate Brackets
• Allows attaching cabled secondary to an
existing neutral bracket provided midspan
clearances are maintained and the cabled
secondary is kept away from the neutral to
avoid chafing.
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Rule 242, Grades of
Construction for Conductors
• Requires conductors crossing navigable
waterways requiring crossing permits to be
designed to Grade B construction.
• Proposed because of downed overhead
conductors hampering rescue craft during storm
recovery efforts.
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Revision of Sections 25, 26 & 27
• Begins incorporating the Reliability Based Method for
determining structure loading.
• New extreme ice and concurrent wind loading map
(from ASCE 7) based on 50 year ice and wind
events.
• Provides a new formula for extreme wind loads.
• Maintains the 60’ exclusion for extreme ice and
concurrent wind and extreme wind loading.
• Establishes a sunset date of July 31, 2010 for use
of the “old” load factors and strength factors
method.
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EXTREME WIND LOADING
FORMULA
• Load in pounds = 0.00256 (V2) (kZ) (Grf) ( I ) (Cf) (A)
• 0.00256 =Velocity-pressure numerical coefficient
• V2 = Basic wind speed in miles per hour (squared)
• Kz = Velocity pressure exposure coefficient. This
value is defined in Rule 250C1, Table 250-2.
• Grf = Gust response factor defined in Rule 250C2.
• I = Importance factor, 1.0 for utility structures and their
supporting facilities
• Cf = Shape factor from Rule 252B2.
• A = Projected wind area in square feet
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Rule 261A3, Table 253-1,
Table 261-1A, Fiber-Reinforced
Polymer Structures
• Addresses the strength requirements and the
strength factors for fiberglass poles and
crossarms.
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Rule 351C1 & 2, Location &
Routing, Other Conditions
• The 5 foot horizontal clearance will apply only
to below ground pools.
• Recommends that DB UG cable should not be
installed directly under buildings or other
structures (below ground pools) unless the
structure is suitably supported to limit transfer of
a detrimental load onto the cable.
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Rules 410A3 & 420I2;
Tables 410-1 & 410-2
• Requires that by January 1, 2009, an arc
assessment be performed for employees that
work on or near energized parts.
• If exposure > 2 cal/cm2, FR clothing shall be
worn.
• In lieu of performing an arc hazard analysis for
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V < 1000V, FR clothing with a min resistance
of 4 cal/cm2 shall be required.
• For V > 1000V, use Tables 410-1 & 410-2 or
perform an arc hazard analysis to determine FR
clothing requirements.
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Rule 420Q, Communication
Antennas
• Prohibits workers from being exposed to
radiation levels greater than those set forth by
the administrative authority for:
3 kHz < f < 3 GHz.
OHSA 1910.97 Subpart G
OSHA 1910.268 Subpart R
FCC Bulletin 65
IEEE Std. C95.1-2005
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QUESTIONS?
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