®
®
Seminar on Significant Changes to NESC 2012 National Electrical Safety Code. ®
Safety Tip Always know your surroundings. ®
–
Where is nearest fire extinguisher? Where is nearest phone? Who would you call for emergency help? Where is nearest fire exit? What if that exit blocked?
Presented to FECA Conference Date: 06/12/12 Presenter: Thomas Blair, P.E.
®
Housekeeping Issues
®
®
CEUs • Make sure you name & PE number is correct on certificate at end of session.
Restrooms Cell phones/pagers Breaks Introductions Questions
® ®
Disclaimer:
®
Disclaimer:
The views and opinions expressed in this tutorial are purely the author’s and shall not be considered an official position of the IEEE Standards Association, American National Standards Institute (ANSI), The Accredited Standards Committee C2-2012, or any of its Technical Committees or Working Groups and shall not be considered to be, nor be relied upon as, a formal interpretation or promotion of the IEEE/ANSI C2 2012 standard, IEEE, ANSI, or any of its Technical Committees or Working Groups.
Disclaimer: ® ®
Readers are encouraged to refer to the standard, the institutions responsible for the information contained therein and contact the institutions directly for official interpretations or clarification of any i tems of interest. NESC INTERPRETATIONS http://standards.ieee.org/ab http://standards .ieee.org/about/nesc out/nesc/inter /inter ps.html Form available in word online:
1
OBJECTIVES
®
®
•NESC scope •Basic purpose and provisions •General NESC overview •Review basic 2007 arc flash requirements •Review NESC-2007 NESC-2007 to NESC-2012 changes •2017 NESC update cycle reviewed.
NESC 2012
®
• 2012 Edition published on August 1, 2011 • Effective January 1, 2012 Summary of Changes – Updated scope, application, and definitions. Simplified minimum approach tables (MAD) Simplified voltage exposure for arc flash Added K factor for wire attention Added clarification of underground portions of guys and swimming pools.
NESC 2012
®
®
®
Is the NESC a Legal Document? •The NESC is a voluntary standard. •Some editions and some parts of the Code have been adopted, with and without changes, by some states and local jurisdictional authorities.
NESC 2012
®
NESC 2012
®
®
®
•Rules for founded upon the fundamental principles used for safety of utility facilities •NESC is not intended as a design specification or an instruction manual •NESC is globally accepted as good engineering practices
OSHA Interpretation November 22, 2005 •Please note that while OSHA does not enforce national consensus or industry standards directly, OSHA may consider such standards, including the National Electrical Safety Code (NESC), published by the Institute of Electrical and Electronic Engineers, Inc., when determining whether a hazard is "recognized" and whether there is a feasible means of abating such a hazard.
NESC FORMAT
® ®
•Divided into four (4) sections, four (4) parts and 5 appendixes: –Section 1- Introduction to the NESC –Section 2- Definitions of Special Terms –Section 3- References –Section 9- Grounding methods for e lectric supply and commun communication ication facilities
2
NESC FORMAT
®
®
–Part 1 (Sec 10 – 19) - Electric supply stations –Part 2 (Sec 20 – 29) - Safety rules for overhead lines –Part 3 (Sec 30 – 39) - Safety rules for underground lines –Part 4 (Sec 40 – 44) - Work rules for supply & communication lines & equipment.
NESC Part 2
®
•Rules for the installation and maintenance of electric supply stations and equipment –Purpose and scope –Protective arrangements in electric supply stations –Installation and maintenance of equipment –Rotating equipment –Storage batteries –Transformers and regulators –Conductors –Circuit breakers, re-closers, switches and fuses –Switchgear and metal-enclosed bus –Surge Arresters
NESC Part 3
®
®
®
•Safety rules for the installation and maintenance of overhead electric supply and communication lines –Purpose, scope and application of rules –General requirements –Relationships between various classes of lines and equipment –Clearances –Grades of construc construction tion –Loading for grades B and C –Strength requirements –Line installation i nstallation
NESC Part 4
®
NESC Part 1
®
®
®
•Work rules for the operation of electric supply and communication lines and equipment –Purpose and scope –Supply and communication systems - Rules for employees –General rules for employees –Additional rules for communication employees –Additional rules for supply employees – General – Energized conductors or parts – Switching control procedures – Work on energized lines and equipment – De-energizing equipment or lines to protect employees – Protective grounds – Live work – Protection against arcing and other damage while installing and maintaining insulators and conductors
•Safety rules for the installation and maintenance of underground electric supply and communication lines –Purpose, scope and application of rules –General requirements applying to underground lines –Underground conduit systems –Supply cable –Cable in underground structures –Direct-buries cable and cable in duct not part of a conduit system –Risers –Supply cable termination –Equipment –Installation in tunnels
®
NESC APPENDIXES ®
5 Appendixes – – Appendix A – Uniform system of clearances (adopted 1990) – Appendix B – Uniform clearance calculations for conductors under ice and wind conditions (adopted 2007) – Appendix C –Example applications for Rule 250C Tables 250-2 and 250-3 – Appendix D –Determining maximum anticipated per unit overvoltage factor (T) at the worksite – Appendix E – Bibliography
3
NESC 2012
®
Section 1
®
®
®
What are the changes between 2007 and 2012?
010B - Necessary for the safeguarding of: –The public –Utility workers (employee and contractors) –Utility facilities –Electric supply and communication equipment connected to utility facilities, and –Other facilities or premises adjacent to or containing utility facilities. (Clarification of purpose but not change!)
®
SCOPE
® ®
®
NESC – NEC
011A - NESC covers: –Supply and communication facilities including metering and associated work practices employed by: •Public or private electric supply •Communications •Railway utility facilities •Trolley utility facilities •Street and area lighting
WHERE IS THE LINE OF DEMARCATION BE BETWEEN THE TWO CODES?
SCOPE
® ®
011A2 - The generation, transmission, and distribution of electricity, lumens, communication signals and communication data through public and private utility systems that are installed and maintained under the exclusive control of utilities or their authorized representatives.
SCOPE
® ®
011B - NESC does not cover: – Wiring located beyond service point – Underground mine wiring – Ship installation – Railway rolling equipment – Aircraft – Automotive Equipment – Luminaries not under exclusive control of utility – Industrial complex not under exclusive control of utility.
4
SCOPE
®
®
011B – Not Covered by NESC –Any facilities that are not an integral part of a generating plant, substation, or control •Office buildings, warehouse, garage, etc. –Premise wiring located beyond utility service points to building or outdoor installations •Underground mine wiring or installations in ships, railway rolling equipment, aircraft and automotive equipment.
NEC 2008
®
–Utility owned premises covered by NEC (continued) •Luminaries not installed or maintained under the exclusive control by utilities •Industrial complex or utility interactive systems that are not controlled exclusively under utilities or qualified persons or are located on the premises wiring side of the service point.
®
Section 90.2(B)(5): Exceptions (5) Installations under the exclusive control of an electric utility where such installations •
•
•
a. Consist of service drops or service laterals, and associated metering, or b. Are located in legally established easements, rights of way, or by other agreements either designated by or recognized by public service commissions, utility commissions, or other regulatory agencies having jurisdiction for such installations, or c. Are on property owned or leased by the electric utility for the purpose of communications, metering, generation, control, transformation, transmission, or distribution of electric energy.
NESC Section 1
®
NESC Section 1
®
®
SCOPE
®
®
®
Introduction to NESC– - 010 and 011—Clarified. Extensive language revisions to the purpose and scope clarify the actual, practical application of the NESC versus the NEC and other standards that have been established since the emergence of the NESC as a national standard. These are clarifications, not substantive changes.
NESC Section 2
® ®
- 014—Wavers, Clarified. Waiver of burial depth requirements during emergencies was recognized here in addition to Rule 311C.
Definitions —area lighting—New. Installation supplying lumens. Exclusive control -> NESC; else NEC applies. Definition supports revisions to Sec. 1.
- 015D—Intent, Clarified. Application of EXCEPTIONs is clarified—they are safe utility options.
—authorized person—New. Person authorized by utility to perform specified duties on utility facilities. Definition used in Part 4 and Sec. 1.
- 016—Effective Date, Revised. Effective date changed to first day of month after 180 days from publication date.
—conductor. 9. lateral conductor, Revised— Clarified. Horizontal, vertical, or diagonal jumper to make connections to line conductor on a common structure.
5
NESC Section 2
®
NESC Section 2
®
®
®
—conductor. 12. Vertical conductor—New. Risers and vertical portions of lateral conductors
—exclusive control – New Convers installation, operation, maintenance by qualified persons. (support section 1)
—delivery point—New. Point at which one utility delivers signals or energy to another utility, as opposed to the service point to a customer.
—exclusive control of utility.—New Where (a) separated from public access and (b) utility responsible for operation. (support Section 1)
—effective ground/effectively grounded—Clarified. Bonding requirements and purpose are clearly specified. —effectively grounded neutral—New. Requirements and purpose are clearly specified. Not less than 4 grounds per mile. Sized for fault current and successful operation of OCPD.
NESC Section 2
® ®
®
—Lines. 1. communication lines.—Revised. Requirements for communication lines located in the supply space (b) versus the communication space (a). FO cables are communication lines regardless of supply or communication space location. —Lines. 2. electric supply lines.—Revised. Fiber-optic lines are communication lines, but supply conductors to light amplifiers are supply lines. —Lines. 3. joint-use lines.—New. Joint-use refers to two or more utilities on the same line. Multiple types of service (i.e. lighting and CATV) by one company is not a joint use line.
NESC Section 2
®
NESC Section 2
®
®
—Supervised installation.—New. Maintained and supervised such that only qualified personnel monitor and service the system. —Supported facility.—New. An overhead component supported on but not providing structural support to an overhead structure.
—Premises.—New. Land and buildings of a user on the user side of the service point. —Premises wiring (system).—New. Interior and exterior wiring on user side of service point to outlets. —Service point.—New Note NOTE. An informative discussion of (1) determination the location of the service point and (2) application of the NEC and NESC relative to the service point.
NESC Section 2
® ®
—Utility.—Revised. An organization responsible for the engineering and supervision of the design, construction, operation, and maintenance of a public or private electric supply, communication, area lighting, street lighting, signal, or railroad utility system. Public utility & Private utility.-NEW – added are sub-definitions of public and private utilities. One customer = private utility. Multiple customers = public utility.
6
NESC Section 2
®
®
—Utilization equipment.—Revised. Uses electric energy or light energy on the premises wiring side of the service point. —Vault.—Revised. A structure on an underground system (Part 3) [not an electric supply station (Part 1)].
NESC Section 9
®
References Updates and additions; IEEE 100 (dictionary) and IEEE 1313 (Power Systems-Insulation Coordination) removed
NESC Section 9
®
®
®
Grounding Methods —091—Scope, Revised. Items required to be effectively grounded must meet the new definition of effectively grounded. —093D1—Grounding conductor, guarding & protection, Revised. Guarding is required for grounding conductors of singlegrounded systems, unless not accessible to the public. —093D2—Moved. Multi-grounded system does not require guarding.
NESC Part 1
®
NESC Section 3
®
®
®
Electric Supply Stations 110A2—Safety Clearance Zone, Revised. Reduce requirements for safety clearance zone to live parts behind solid portion of station fence and new Figure 110-2 was added.
—094B7—Grounding Electrodes, directly imbedded metal poles, Revised. Exception allowed if supported by qualified engineering study. Still requires 1.5m (5ft) embedded length exposed directly to earth. Supplemental electrodes must be 6 ft from pole. —099B—Additional requirements, Electrode connection, Revised. Communication grounding conductor size increased from AWG No. 14 to AWG No. 6.
® ®
NESC Part 1
7
NESC Part 1
®
NESC Part 1
®
®
®
110B2, Arrangement, room and space, Use, Exception 1—Revised. Added storing vehicles in stations is recognized use of space. 111A1—Illumination, normal condition, Revised. Outdoor lighting not required at unattended stations. Table 111-1—Revised. Illumination requirements for generating stations and substations was simplified (shorter list).
NESC Part 1
®
NESC Part 1
®
®
®
114 Fire extinguishing equipment, Exception—New. Fire extinguishing equipment is not required in unmanned, outdoor substations without a control (or similar) building.
NESC Part 1
® ®
124A1—Guarding live parts, where required, Revised. Guards are now required around energized parts (>300V) with clearance to outer fence less than that required by 110A2. 124D—Taut-String Distances, New. Vertical clearances to equipment bushings are tautstring distances up the side and over to the part—codified an earlier IR.
NESC Part 1
® ®
Figure 124-3 New – Tautstring measurement of vertical clearance to energized parts of equipment or behind barriers.
8
®
NESC Part 2
®
Seminar on Significant Changes to NESC 2012 National Electrical Safety Code. ®
®
Overhead General 214A4—Inspection of lines, records, Revised. Title change (Inspection records Record of defects) plus inspection records of conditions or defects affecting compliance must be maintained until correction.
Class Break End of part 1 Part 2 next
NESC Part 2
®
®
Overhead General 214A5—214A4—Inspection of lines, corrections, Revised. Title change (Corrections Remedying defects) plus conditions or defects reasonably expected to endanger life or property must be promptly corrected, disconnected, or isolated.
NESC Part 2
®
NESC Part 2
®
®
®
215C4—215C4—Insulators in anchor guys, Old C5 renumbered to C4 and revised. Now covers only insulators in anchor guys. Insulator positions are specified to limit opportunity for the public area or other facilities on the structure to be energized through guy contact if a portion of the guy becomes energized.
215C1—Grounding, non current carrying parts, general, New NOTE under Exception 1. If a decision is made to ground all items above 8 ft level, old ungrounded ones are not required to be grounded. Then added Note: Typical practice is to ground old items when doing other significant work on the structure. 215C4—Insulators in guys, Moved. Span wires carrying railroad or trolley contact conductors. These are included in 215C6.
NESC Part 2
® ®
215C5—Insulators in span guys, Modified. To cover insulators in span guys and added wires supporting luminaires and traffic signals. Requirements similar to the new 215C4.
Prevent energization of guy wire within 8 feet of ground to protect public.
9
NESC Part 2
®
®
217A1a—Protection of structures, Revised. Physical protection for structures is required only in parking lots, in alleys, or next to driveways where subject to vehicular traffic abrasion that might affect strength. 217A2b—Readily climbable structures, Addition. Structures must be attended or climbing barriers installed whenever temporary steps are attached to the structure < 8ft from ground.
NESC Part 2
®
217A4 & A5—deleted and replaced with new A4. Attachments, decorations, and obstructions require permission of structure owner Non-utility attachments require permission of occupants of the space involved. Attachments cannot cause noncompliance with NESC or obstruct climbing. Through-bolts must be trimmed.
NESC Part 2
®
®
®
218 - Vegetation Management 218A1—Addition. New NOTE 2 recognizes the impracticality of prevent all treeconductor contacts on overhead lines.
NESC Part 2
®
NESC Part 2
®
®
®
Overhead Clearances – 230A3—Measurement of clearance, Revised. Live metallic hardware connected to supply or communication line conductors is considered part of those conductors. 230A4—Rounding of calculations, Revised with addition. If a calculated clearance is allowed to be reduced by footnote or EXCEPTION, it shall first be rounded up, then reduced per allowance, and the result shall also be rounded up. An example was added.
218B1—Crossings, Addition. Crossings now include navigable waterways requiring crossing permits. Crossing and adjacent spans should be kept free of overhanging or decayed trees or limbs that might fall into line.
NESC Part 2
® ®
230B Ice and wind loading for clearances, and Figure 230-1, Table 230-1, and Table 230-2— Addition. A new Clearance Zone 4 was added for warm islands in latitudes less than 25 degrees. Temperature of 50ºF and no ice below 9000 ft altitude; 15 ºF and 0.25 in radial ice at higher elevations.
10
NESC Part 2
®
®
NESC Part 2
®
NESC Part 2
®
®
®
Vertical Clearances Table 232-1—Revised Title of Category 4 added commercial and industrial sites to the list of areas subject to truck traffic. Tables 232-1, 234-1, 234-2, 234-3— Revised. Ungrounded portions of guys added to column titles and some NOTES. ERRATA
NESC Part 2
®
NESC Part 2
®
®
®
234B—Clarified. These clearances also apply above intermediate poles in the same line in skip-span construction. 234C Clearance from buildings, etc, and Table 234-1—Clarified. Flagpoles, flags, and banners were added to the list of other installations covered by Part 2 of Table 234-1.
Table 232-2—Revised. Title of Category 1c added commercial and industrial sites to the list of areas subject to truck traffic and FN 26 of Table 232-1 was added as FN 3. 233B—Horizontal clearance, Revised. Maximum operating voltage is required for circuits above 50 kV to ground. Between different circuits, phasor difference voltage is now used for horizontal clearances (when unknown, assume 180O).
NESC Part 2
® ®
234C3c—Clearance of supply conductors attached to buildings, Clarified with new Exception for service drop. Allows reduction at attachment point to 1in. The Footnote from Table 235-6 that had been omitted when the value of 3 in was copied from the table in 2007 was added to recognize that the common house attachment insulators do not always provide the full value of the rule.
11
NESC Part 2
®
®
234C3d(1) Clearance to buildings, Exception 1—New. The language of old Footnote 14 (now FN 12) from Table 234-1 for railings, walls, or balconies was added to the rule. (ERRATA reassigns FN back to FN 14). 234E1 NOTE—Clearance to pools, New. The new NOTE clarifies that swimming pool clearances do not apply for hot-tubs and other equipment that do not employ rescue poles and skimmer poles.
NESC Part 2
®
NESC Part 2
®
®
Table 234-1—Clearance Table, Revised Notes. Porches and decks were added in with roofs and balconies in FN12 (ERRATA). Flagpoles, flags, and banners were added in FN15 (To clarify treatment of windblown flags) (ERRATA). FN 11—Deleted. No longer appropriate. FN 16—Added. To match FN 26 of Table 232-1 if oversized vehicles are expected above loading ramps, etc. (ERRATA)
NESC Part 2
®
®
®
Clearance between conductors235B1b—Horizontal clearance, fixed supports, Clarified. When using the formula for fixed conductor clearance to determine maximum allowable sag for a clearance, round the resultant down.
235C2b1b—Additional vertical clearance, Clarified. Both Exceptions (3% per 300m above 1000m & clearance above 50kV based on Max operating voltage) previously under (1)(a) were moved after (1)(b), since applies to > 50kV.
235C—Vertical clearance between conductor and support, Clarified. The clearances apply to both line conductors and to lateral conductors at the support (see definitions), not just line conductors.
235C2b1ci Exception—New. The temperature differentials do not apply to conductors of the same circuit installed the same way that are simultaneously deenergized.
NESC Part 2
® ®
235G4—Conductor spacing, Deleted and added back as two Exceptions to G3. Neutrals of 230C3 cables and messengers of 230C1 cables may attach to the same insulator as a line neutral, so long as clearances of Table 235-8 are maintained in mid-span and insulated energized conductors are held away at attachments.
NESC Part 2
® ®
Vertical clearance between communication and supply. 238A—Clarified. Communication antennas, and metal or nonmetallic supports or braces associated with communication cables or conductors are among the items to be considered as equipment for this rule.
235H—Clearance between comm lines, Revised. Pole owners must concur with agreements for reduced clearance and spacing between communication facilities.
12
NESC Part 2
®
NESC Part 2
®
®
®
Grades of construction – Tables 242-1—Revised. Table 242-1 now incorporates requirements of deleted Table 242-2. 242-2—Deleted. Accommodates merging Table 242-2 into Table 242-1.
General Loading for Grades B and C. 250B, Table 250-1 and Table 251-1— Revised from 3 loading zones to 4 loading zones to add warm island loading. A new Warm Island Loading case was added for warm islands in latitudes less than 25 degrees north or south. Temperature of 50 ºF, 9 psf wind, and no ice below 9000 ft altitude; 15 ºF, 4 psf wind, and 0.25 in radial ice at higher altitudes. Agrees with Section 23.
NESC Part 2
®
®
®
®
250C1, 250C2, and Table 250-2—Revised. Application of and velocity pressure exposure coefficients (kZ) (height adjustment) and gust response factors(GRF) were revised to facilitate calculations of wind forces on portions of a structure or supported facilities at a specific height. Formulas must be used to calculate height adjustments for specific heights.
®
NESC Part 2
® ®
®
Wind Loading
13
NESC Part 2
®
®
®
®
Table 251-1—Added note. Clarified application of the K factor for wire tensions when messenger supports multiple conductors using spaces. ―… when each conductor is separately loaded with ice and wind … the K factor should be applied to all cables.‖ Also added warm island location.
NESC Part 2
®
®
Load Factor Calculation. 253—Revised. Language changed to reflect deletion of Table 253-2 – Alternate load factors for wood and reinforced concrete structures. Table 253-2—Deleted. Alternate method for wood and reinforced concrete no longer allowed.
NESC Part 2
®
NESC Part 2
®
®
®
261B—New NOTE 2. Soil saturation can reduce strength of foundations, settings, and guy anchors. 261H1—Revised. Addresses tensions of overhead supply conductors / shield wires. Added tension limits when Rule 250C (extreme wind loading) and 250D (extreme ice with concurrent wind loading) loads apply. Now limited to 80% of the rated breaking strength when those extreme load conditions are applied with load factor of 1.0.
Strength requirements 260B, 261A1, 261A2a, 261A2b(3), 261D2a(2), 261D3 and Table 261-1A— Text revised or deleted. Language changed to reflect deletion of the alternate method of calculation of load factors for wood and reinforced concrete structures (also Tables 253-2 and 261-1B removed dealing with same topic).
NESC Part 2
® ®
261H1 (continued) - Also modified application of secondary conductor tension limit from 15OC(60OF) to the colder temperatures of Table 250-1. Should be used for Aeolian vibration checks. Brings into line temp limits of OEMs and reduces risk of conductor damage due to Aeolian vibration. Exception allows higher temperatures above Table 250-1, but not higher than 15OC(60OF), if vibration is controlled or Aeolian vibration damage is unlikely to occur under the controlling conditions.
14
NESC Part 2
®
®
Strength Factor Table Table 261-1—Revised footnotes. When new or changed facilities modify the loads, the new loads must be used to determine the required strengths of the affected structural components.
NESC Part 3
®
Line insulation Table 277-1—Revised. New insulator standards were added and several strength ratings were revised. 279A1b—Revised. Dry and wet flashover values of insulators determined by ANSI C29.1. Also, UV protection is required for fiber reinforced polymer and other guy insulators affected by ultraviolet light.
NESC Part 3
®
®
®
Underground – 313A4—Inspection, Revised. Title change from ―Record of Defects‖ to ―Inspection Records‖. Edited to ―Any conditions or defects effecting compliance … shall be maintained. Requires records of conditions or defects affecting compliance must be maintained until correction.
NESC Part 3
®
NESC Part 2
®
®
®
Underground – 313B – Deleted voltage level of > 300V for grounding riser guards and ducts. 320B5 – Separation of systems, Revised. Requires not less than 300 mm (12in) separation from gas and other lines transporting flammable materials (distance not previously specified).
313A5—Correction, Revised. Title change from ―Remedying defects‖ to ―Corrections‖. Implies conditions or defects reasonably expected to endanger life or property must be promptly corrected, disconnected, or isolated. Section 32 (Underground conduit systems) NOTE 2—Clarified. Both supply and communication cables in duct not part of a conduit system must meet Section 35, not Section 32. (section 35 modified to include both direct buried cable and cable in duct not part of conduit system).
NESC Part 3
® ®
323E5—Vaults, New. If ventilation openings in above ground vaults are not protected against intrusion of sticks, etc. by baffles or louvers, energized parts must be located away from the opening to meet clearances of Rule 110A2 and Table 110-1.
15
NESC Part 3
®
Figures 323-1 and 323-2 – Revised. Complies with latest ASTM C857
®
®
NESC Part 3
®
®
NESC Part 3
Direct buried 350F & G—New Recommendation. If color codes are used on underground cables, use the APWA Uniform Color Code. Cable in Duct 352A2—New. Backfill and trench should limit opportunity for damage to the duct.
NESC Part 3
®
®
®
352A2 – New. Cable in duct. Requires bottom of trench to be smooth earth to protect cable from damage.
352D1 & 2 and Table 352-1—Addition of duct. Duct must meet same requirements as cable for burial depth. If a duct is strong enough to resist forces from surface usage, lesser depths may be used without additional protection. 354A2—New Exception. Supply cables up to 300V can have less than 12 inches clearance from steam lines, gas lines, etc., if fault will not damage the other lines and affected parties agree.
NESC Part 3
® ®
355—New. Requirements for duct not part of a conduit system are specified, similar to those for conduit. A corrosion resistant, B internal surface of duct smooth, C duct joints adequate to prevent soil intrusion, D duct through walls shall be sealed To prevent entrance of gas.
NESC Part 3
® ®
380D—Equipment, general, New Exception 2. Allows reduced clearances from pad-mounted equipment to fire hydrants if fire authority and utility agree. 384 – Equipment, installation, Rewritten. Requires bonding between aboveground metallic communication and supply enclosures within 1.8m (6ft) separation or less only.
16
®
NESC Part 4
®
Seminar on Significant Changes to NESC 2012 National Electrical Safety Code. ®
®
Work Rules – Section 41 – Rules for EMPLOYERS Section 42 – General Rules for EMPLOYEES Section 43 – Additional Rules for communication EMPLOYEES Section 44 – Additional Rules for supply EMPLOYEES
Class Break End of Part 3 Start of Part 4
NESC Part 4
®
®
Work Rules – Substantial changes to arc flash protection section. Significant testing done by two separate major utilities and a research institute, providing the opportunity to establish appropriate incident energy levels for many common industry applications. The result of the review of the testing supported the development of new Table 410-1 that establishes arc energy thresholds for different equipment/exposures at voltage levels below 1KV.
NESC 2007
®
NESC 2007
®
®
®
Low voltage arc exposure <1000 Volts (2007 NESC) The effective arc rating of clothing or a clothing system to be worn at voltages 1000 V and above shall be determined using Tables 410-1 and 410-2 or Performing an arc ha zard analysis. EXCEPTION 2: For secondary systems below 1000 V, applicable work rules required by this part and engineering controls shall be utilized to limit exposure. In lieu of performing an arc hazard analysis, clothing or a clothing system with a minimum effective arc rating of 4 cal/cm2 shall be required to limit the likelihood of ignition.
Arc Exposure (2007 NESC) Effective as of January 1, 2009, the employer shall ensure that an assessment is performed to determine potential exposure to an electric arc for employees who work on or near energized parts or equipment. If the assessment determines a potential employee exposure greater than 2 cal/cm2 exists (see Neal, Bingham, and Doughty [B59]), the employer shall require employees to wear clothing or a clothing system that has an effective arc rating not less than the anticipated level of arc energy.
NESC Part 4
®
Work Rules – 410A3—Revised. Recognizes exposures less than 1KV. Either a detailed arc hazard analysis or Table 410-1, 410-2, or 410 -3 must be used to determine the effective arc rating of clothing or clothing systems to be worn working above 50 V. Evaluation based on available fault current, duration of arc, and distance from arc to employee. ®
Table 410-1 <1kv Table 410-2 1.1kv to 46kv Table 410-3 >46.1kv Based on 15‖ separation
17
NESC Part 4
®
®
Table 410-1—New 50V to 1kV Table. Calorie per cm2 clothing rating requirements are shown by equipment type and voltage. These values can be used in lieu of calculating values. Old Tables 410-1 and 410-2 were renumbered to 410-2 and 4103. Note – Table 410.1 values determined by testing. Table 410.2 and Table 410.3 determined using software (not testing).
NESC Part 4
®
NESC Part 4
®
®
410A3 continued— Exception added if PPE creates greater hazard then arc hazard, reduced effective arc rated clothing allowed. Changed original Note 1 to Note 2- Added natural fiber to non-flame resistant material. Changed original Note 2 to Note 3- Added –Utilizing engineering controls to reduce arc energy levels and work practices to reduce arc energy levels.
®
®
®
Example – Engineering Controls and Work Practices to reduce arc energy levels
NESC- 2012
® ®
®
Industry testing on 480V network protectors indicates arcs will not self-extinguish and heat flux rates will exceed 60 cal/cm 2 /s at 24 in working distance. Perform arc hazard analysis. (See Eblen and Short [B31].) Footn ote 11-
Industry testing on panelboards with edge-mounted, parallel bus bars indicate arcs will not self-extinguish and heat flux rates will exceed 60 cal/cm2 /s at 18 in working distance. Perform arc hazard analysis. (See Eblen and Short [B31].) Footn ote 13-
Other Footno tes-
NESC Part 4
®
Table 410-2 (old 410-1)—Moved. Old Table 410-1 was renumbered. Table 410-2- Clothing and clothing systems voltage, fault current and maximum clearing times for voltages 1.1 kV to 46 kV ac
Many that relate to testing
criteria
18
®
NESC Part 4
® ®
®
Table 410-3 (46.1kV-800kV) (old 410-2)—Revised. Maximum clearing times allowed for 4, 8, and 12 calorie systems were updated (generally increased). Major changes throughout the table
®
NESC- 2012
® ®
®
Supporting Comments Subcommittee 8 – •Established a low-voltage arc flash work group (WG). –Evaluate minimum clothing or clothing system requirements for employees working on voltages less than 1000 volts.
NESC- 2012
® ®
Supporting Comments Subcommittee 8 – •PG&E completed tests during 2008 to determine the arc flash characteristics of 480 V self-contained metering equipment by creating fault conditions at various kA levels. -WG collaborated with PE&G on tests. -Application of an accepted industry standard (IEEE-1584-IEEE Guide for Performing Arc Flash Hazard Calculations-2002)
NESC- 2012
® ®
Supporting Comments Subcommittee 8 – •The new table (410-1) uses an 18 inch worker separation. –Unlike the existing higher voltage tables in NESC-2007 which uses a 15 inch worker separation. •The WG committee based the change on the application of IEEE 1584 test methodologies and typical working distances for low-voltage motor control centers and panel boards. •The employee working distance is based on the incident energy on the worker’s face and body not on the hands and arms.
19
NESC 2012
®
NESC 2012
®
®
®
410A3– Requires each employer to perform an arc hazard assessment (using tables or calculations) for employees who work on or near energized lines, parts or equipment at 50V to 800 kV. Assess both hazard level and risk (probability) of incident occurring.
Requires employers to determine the effective arc rating of clothing or clothing systems to be worn by employees working on or near energized lines, parts, or equipment at voltages 50V-800 kV by one of the following methods: – Employers perform a detailed arc hazard analysis – Use tabulated values in tables provided. • Table 410-1 (50V-1000V) • Table 410-2 (1.1kV-46kV) • Table 410-3 (46.1kV-800kV)
NESC 2012
®
®
410A3b – New Note 1: Assessments performed to determine potential exposure to an electric arc consider the affected employee’s assigned tasks and/or work activities. - Highlights difference between incident energy level and HRC (Hazard) where - Hazard is function of both incident energy level and probability of incident occurring.
NESC 2012
®
NESC 2012
®
®
®
410B. Revised - Emergency procedures and first aid rules procedures –Change in wording from conspicuous locations to kept accessible. Ensures copies of emergency and first aid procedures are accessible to employees where they work.
410A3b Changed original Note 1 to Note 2– Added natural fiber to non-flame resistant material. • Changed original Note 2 to Note 3Added – Utilizing engineering controls to reduce arc energy levels and work practices to reduce exposure levels.
NESC 2012
® ®
411C. Inspection and testing of protective devices and equipment –Changed terms line worker's body belts, lanyards and positioning straps and other personal equipment to: •Climbing fall protection equipment. Requires an inspection before use to ensure the climbing and fall protection equipment are in safe working condition.
20
NESC 2012
®
®
411F2. Revised, Fall Protection –Non- locking snap hooks shall not be permitted.
NESC 2012
® ®
General Precautions 420K6—Revised. Non-locking snap hooks are now prohibited.
NESC Part 4
® ®
General operating routines 421A6 – New. Conduct a job briefing before each job. Includes; –Hazards associated with the job. –Work procedures involved –Special precautions –Energy source controls –PPE requirements. NESC-2007 does not contain a specific requirement to conduct a job briefing.
NESC Part 4
®
NESC Part 4
®
®
®
Approach to energized conductors / parts 431C—New. When repairing underground communication lines in joint use with damaged supply lines, treat all communication and supply lines as energized or assure that the supply lines are de-energized.
Overhead line operating procedures 422A2—Revised. Contact with trucks or other equipment setting poles, etc., in vicinity of energized lines must be avoided—even if the equipment is grounded. •NESC-2007 words not bonded to an effective ground was removed. •States: Contact with trucks, or other equipment that is being used to set, move, or remove poles……… shall be avoided by employees standing on the ground or in contact with grounded objects unless employees are wearing suitable protective equipment.
NESC Part 4
® ®
Communication work MAD table. Table 431-1—Revised. The approach distances were revised using IEEE Std 5162009 calculations. Some values changed an inch or so. Transmission voltages were subdivided to give more flexibility.
21
®
NESC 2012
® ®
®
Section 44. Additional Rules For Supply Employees •441. Energized conductors or parts (MAD tables) Complete Rewrite •Table 441-1 –AC live work minimum approach distance •Table 441-2 –DC live work minimum approach distance •Table 441-3 –Altitude correction factor •Table 441-4 –Maximum use voltage for rubber insulting equipment
NESC 2012
®
NESC 2012
®
®
®
Minimum Approach Distances (MAD) OSHA – the closest distance an employee is permitted to approach and energized or a grounded object NESC – the closest distance a qualified employee is permitted to approach either an energized or a grounded object, as applicable for the work method being used IEEE 516 - the minimum air insulation distance (MAID) plus a factor for inadvertent movement
Minimum Approach Distances (MAD) –Problem •IEEE 516-2009 •Major changes were made in regards to MAD distances in IEEE 516-2009. •OSHA reopened the comment period two times to ensure time for IEEE 5162009 to be approved.
(516-2009 - IEEE Guide for Mai ntenance Methods on Energized Power Lines)
NESC 2012
®
Minimum Approach Distances (MAD) OSHA - 1910.269 and 1926 in Subpart V NESC - in Part 4 Rules for the Operation of Electric Supply and Communication Lines and equipment IEEE 516 - IEEE Guide for Maintenance Methods on Energized Power Lines
NESC 2012
®
®
®
Minimum Approach Distances (MAD)
In NESC since early 1900’s Recent years based on IEEE 516 calculation method IEEE 516 repeatedly changed since inception NESC has followed those changes IEEE 516 2009 changes begs the question ―Why change again?‖
22
NESC 2012
®
®
Minimum Approach Distances (MAD)
NESC 2012
®
®
Minimum Approach Distances (MAD)
Error discovered in phase-to-phase calculations Phase-to-ground air saturation factor used to calculate phase-to-phase MAD Discovered error -> deemed some OSHA and NESC MAD values incorrect Must correct in OSHA and 2012 edition of the NESC
NESC 2012
®
Most significant changes occur in phaseto-phase voltages above 230 kV Phase-to-phase increases perceived as problems by some SC8 members Working group has met several times to address issue Recently conducted joint meeting with IEEE 516 task group
NESC 2012
®
®
®
IEEE 516 - Minimum Approach Distances
Voltage in kilovolts phase to phase
T - p.u.
Phase to ground
Phase to phase
(ft - in)
(ft - in)
1994 2009 IEEE 2002 NESC 2007 NESC 1910.269 516
1994 2009 IEEE 2002 NESC 2007 NESC 1910.269 516
0 to 0.05
not specified
not specified
0.051 to 0.300
avoid contact
avoid contact
0.301 to 0.750
3
avoid contact
1–0
1–0
1–1
avoid contact
1–0
1–0
0.751 to 15
3
2–1
2–2
2–2
2–2
2–2
2–3
2–3
2–3
15.1 to 36
3
2–4
2–7
2–7
2–5
2–7
2–10
2–10
2–10
1–1
36.1 to 46
3
2–7
2–9
2–9
2–7
2–10
3–2
3–2
3–1
46.1 to 72.5
3
3–0
3–3
3–3
3–0
3–6
3–11
3–11
3–9
72.6 to 121
3
3–2
3–2
3–4
3–4
4–3
4–3
4–7
4–7
121.1 to 145
3
3–7
3–7
3–10
3–10
4–11
4–11
5–4
5–4
145.1 to 169
3
4–0
4–0
4–3
4–3
5–8
5–8
6–0
6–3
169.1 to 242
3
5–3
5–3
5–8
5–8
7–6
7–6
8–2
9–2
242.1 to 362
3
8–6
8–6
9–2
9–1
12–6
12–6
13-6
14-3
362.1 to 550
2.4
11–3
11–3
11–10
11–11
18-1
18–1
19-2
19-9
551 to 800
2
14-11
14–11
15-11
15-10
26-0
26–0
27-10
29-2
Phase-to-ground • MAID – Minimum air insulation distance • MTID – Minimum tool insulation distance • MAD – Minimum approach distance • MAD for tools – MAD with tool in air gap • MHAD – Minimum helicopter approach distance
IEEE 516 MAD TABLE - 121.1 to 145 kV T (p.u.)
Line-to-ground work ®
NESC 2012
Line-to-line work ®
MAID (ft)
MTID (ft) ®
MAD (ft)
MAD for Tools (ft)
MHID (ft)
MAID (ft)
MAD (ft)
MHID (ft)
1.5
1.26
1.39
2.26
2.39
2.49
2.22
3.22
3.54
1.6
1.34
1.48
2.34
2.48
2.58
2.35
3.35
3.68
1.7
1.43
1.57
2.43
2.57
2.67
2.48
3.48
3.83
1.8
1.51
1.66
2.51
2.66
2.76
2.61
3.61
3.97
1.9
1.6
1.75
2.6
2.75
2.85
2.75
3.75
4.12
2
1.68
1.85
2.68
2.85
2.95
2.88
3.88
4.27
2.1
1.76
1.94
2.76
2.94
3.04
3.02
4.02
4.42
2.2
1.85
2.03
2.85
3.03
3.13
3.16
4.16
4.58
2.3
1.93
2.12
2.93
3.12
3.22
3.3
4.3
4.73
2.4
2.01
2.22
3.01
3.22
3.32
3.44
4.44
4.89
2.5
2.1
2.31
3.1
3.31
3.41
3.59
4.59
5.04
2.6
2.18
2.4
3.18
3.4
3.5
3.73
4.73
5.2
2.7
2.27
2.49
3.27
3.49
3.59
3.88
4.88
5.36
2.8
2.35
2.58
3.35
3.58
3.68
4.02
5.02
5.52
2.9
2.43
2.68
3.43
3.68
3.78
4.17
5.17
5.69
3
2.52
2.77
3.52
3.77
3.87
4.32
5.32
5.85
3.1
2.6
2.86
3.6
3.86
3.96
4.47
5.47
6.02
3.2
2.68
2.95
3.68
3.95
4.05
4.63
5.63
6.19
3.3
2.77
3.04
3.77
4.04
4.14
4.78
5.78
6.36
3.4
2.85
3.14
3.85
4.14
4.24
4.94
5.94
6.53
3.5
2.94
3.23
3.94
4.23
4.33
5.09
6.09
6.7
®
Minimum Approach Distances (MAD) •441A New Note 3–Methodology for calculating minimum approach distances (MAD) were taken from IEEE std 516-2009 •Table 441-1 AC live work minimum approach distance –Changes to voltages (301V- 800 kV) –Added distance to employee from energized part (transmission voltages 72.6-800 kV) •Without tools phase-to-ground •With tools phase-to-ground •Without tools phase-to-phase
23
®
NESC 2012
® ®
®
MAD Table Notes 3. Inadvertent movement factors used in these tables are as follows: 0.301 kV to 0.750 kV = 0.3 m (1 ft) 0.751 kV to 72.5 kV = 0.5 m (2 ft) 72.6 kV to 800 kV = 0.3 m (1 ft)
NESC 2012
®
NESC 2012
®
®
®
MAD Table Notes
MAD Table Notes
6. Distances were calculated using the following TOV values: 72.6 kV to 362 kV = 3.0 362.1 kV to 550 kV = 2.4 550.1 kV to 800 kV = 2.0 7. Distances for live line tools in the air gap were calculated by adding a tool factor to the electrical component (IEEE 516 C 2 1.1 tool factor).
8. Phase to phase live line tool in the air gap values are not available. If this situation exists, an engineering evaluation should be performed. 9. With Tools means a live line tool bridging the air bap to the employee from the energized part. 10. For bare-hand work where the employee is at line potential, this distance is to an object at a different potential.
NESC 2012
® ®
Minimum Approach Distances •Table 441-2 DC live work minimum approach distance –Added distance to employee from energized part (transmission voltages 72.6-750 kV) •Without tools pole-to-ground •With tools pole-to-ground
NESC Part 4
® ®
Energized conductors or parts 441A3b2—Clarified. Approach distances apply to reach or extended reach. 441A1—Revised. Approach distances determined by engineering analysis are allowed in addition to Tables 441-1 to 4414. New NOTES explain components of calculations and applicable standards. IEEE Std 516-2009 - IEEE Guide for Maintenance Methods on Energized Power Lines primary reference.
24
NESC Part 4
®
®
441A4—Voltages above 72.5kv Revised. Approach distances NOT determined by engineering analysis must meet Table 441-1 or 441-4 and specified conditions. Blocking of automatic reclosing is required below 242 kV & above 420kV resistor / arrestor used to limit switching overvoltages. Note in above states ―It is recommended to block reclosing during live work on all voltages. ‖.
NESC Part 4
®
NESC Part 4
®
®
441A6—Altitude correction Revised. Values of inadvertent movement from previous 441A7a were moved here, instead of referencing the deleted rule. Values are; 0.301 kV to 0.750 kV = 0.3m (1 ft) 0.751 kV to 72.5 kV = 0.5m (2 ft) 72.6 kV to 800 kV = 0.3m (1 ft ) 441A7—Deleted. Additions of this information to tables and rules elsewhere,
®
®
®
Table 441-4 DC work MAD—Reworked and replaced by table 441-2. The approach distances for DC live line work were revised using IEEE Std 516-2009 calculations. The entire table was restructured. Values below 72.6 kV were added. Values above 72.5 kV are based upon a TOV of 1.8 (the last row of the old table).
®
NESC Part 4
® ®
®
444D— Employees protective grounds Revised. Previous paragraph specifying location of employee protective grounds at or on both sides of work location was deleted and performance requirements were added, including a new NOTE and a new Exception.
25
NESC 2012
®
NESC 2012
®
®
®
444 D. Employee’s Protective Grounds
444 D. Employee’s Protective Grounds
•Remove- Grounds shall be placed at each side of the work location and as close as practical to the work location……… •Add- Temporary protective grounds shall be placed at such locations and arranged in such a manner that affected employees are protected from hazardous differences in electrical potential.
•Note added–Touch and step potentials may exist. –Additional measures may include barriers, insulation, isolation or grounding mats.
NESC 2012
®
®
444D Employee’s Protective Grounds Exception added: –Alternative work methods such as isolation of equipment, lines and conductors from all sources including induced voltages may be employed when the employer has assured worker protection from hazardous differences in electrical potential.
NESC 2012
®
NESC 2012
®
®
®
445. B.3. Removing Grounds •Note 1- added –Hazards due to electric and magnetic field induction may exist when conductors, cables and equipment are parallel or cross other energized circuits. •Note 2- added –References IEEE 1048 and 1246 for personal protective grounding. IEEE-1048 – IEEE Guide for Protective Grounding of Power Lines IEEE-1246 - IEEE Guide for Temporary Protective Grounding Systems Used in Substations
445 Protective grounds Added – Extreme caution shall be exercised that the proper sequence of installing and removing protective grounds is followed. When installing grounds, 1. Connect ground side first. 2. Connect phase conductor last When removing grounds, 1. Remove phase conductor first. 2. Remove ground conductor last
®
Seminar on Significant Changes to NESC 2012 National Electrical Safety Code. ®
Class Break End of Part 4 Appendices & Errata
26
NESC Appendixes
®
®
Table A-1 clearance—Revised editorially. The metric M&E column was moved to the right side of the table. The table now shows in order how the values of M&E are created from the original rigid (R), nonrigid (NR), grounded or insulated(GI), open(O), and mechanical and electrical (M&E) values in feet, then last column to the right is M&E values in metric.
Appendix C—Revised to reflect changes in Rule 250C regarding structural support calculations. Existing examples showing application of extreme wind loading requirements of 250C were revised to match changes in the code terms. New Example 5 was added to illustrate calculations for wind on a lattice tower with a large window section and two separate ground wire support peaks. Appendix E—Revised editorially. Updated with new dates and additional standards.
NESC Errata
®
®
Updated version at: http://grouper.ieee.org/groups/nesc/NESC2012-Edition_Sheet1.pdf
Page 2: There is a typographical error in Rule 011A4. The sentence should contain a closing parenthesis.
Below information is based on Errata issued 6 February 2012
NESC Errata
Page 96: There is an error in item (f) of Footnote 10 that appears at the end of Table 232-1 (m). Item (f) should contain ―215C4 or.‖
NESC Errata ®
(f) Grounded guys, guys meeting Rules 279A1 and 215C4 or 215C5 exposed to 0 to 300 V 2.9
Page 96: There is an error in Footnote 15 that appears at the end of Table 232-1 (m). The word ―215C5‖ should be replaced with ―215C4.‖ 15 The portion of anchor guys be low the lowest insulator meeting Rules 279A1 and 215C4 may have the same clearance as grounded guys.
4. Street and area lights that provide a supply of lumens where these facilities are supplied by underground or overhead conductors installed and/or maintained under the exclusive control of utilities (including their authorized contractors or other qualified persons ).
®
®
NESC Errata
®
®
®
NESC Appendixes
®
®
Page 97: There are errors that appear at the end of Table 232-1 (m). Although Footnote 25 was deleted from the previous version, it should have been listed as follows. Therefore, the inserted footnote should have been shown as Footnote 26. 25 This footnote not used in this edition. 26 When designing a line to accommodate oversized vehicles, these clearance values shall be increased by the difference between the known height of the oversized vehicle and 4.3 m.
27
NESC Errata
®
®
Pages 97, 98, and 99: There is an error in Table 232-1 (ft). The cells in columns 2 and 5 of the header row should state ―(ft)‖ for feet and not ―(m)‖ for meters.
NESC Errata
®
Page 100: There is an error in item (f) of Footnote 10 that appears at the end of Table 232-1 (ft). Item (f) should contain ―215C4 or.‖ (f) Grounded guys, guys meeting Rules 279A1 and 215C4 or 215C5 exposed to 0 to 300 V
®
Page 100: There is an error in Footnote 15 that appears at the end of Table 232-1 (ft). The word ―215C5‖ should be replaced with ―215C4.‖
15 The portion of anchor guys below the lowest insulator meeting Rules 279A1 and 215C4 may have the same clearance as grounded guys.
Although Footnote 25 was deleted from the previous version, it should have been listed as follows. Therefore, the inserted f ootnote should have been shown as Footnote 26.
Page 129: There are three errors in Figure 234-4(b). At the top of the figure, the two instances of ―H‖ should read ―A.‖ The text associated with ―A‖ in the legend should read ―B + 5.5 m (18 ft)‖ and not ―V + 5.5 m (18 ft).‖
25 This footnote not used in this edition. 26 When d esigning a line to accommodate oversized vehicles, these clearance values shall be increased by the difference between the known height of the oversized vehicle and 14 ft.
NESC Errata
®
Pages 130, 131, and 132: There is an error in Table 234-1 (m). The cell in column 6 of the header row should contain ―ungrounded equipment cases, 750 V to 22 kV.‖
NESC Errata
®
®
NESC Errata
®
®
NESC Errata
®
®
®
Page 133: There is an error in Footnote 11 that appears at the end of Table 234-1 (m). The word ―215C5‖ should be replaced with ―215C4.‖ 11 The portion of anchor guys below the lowest insulator meeting Rules 279A1 and 215C4 may have the same clearance as grounded guys.
Although Footnotes 12 and 13 were deleted from the previous version, the remaining footnotes should not have been renumbered. They should be listed as follows: 12 This footnote not used in this edition. 13 This footnote not used in this edition. 14 For clearances above railings, walls, or parapets around balconies, decks, or roofs, use the clearances required for row 1b(1). For such clearances where an outside stairway exists to provide access to such balconies, decks, or roofs, use the clearances required for row 2b(2). 15 Does not include neutral conductors meeting Rule 230E1. 16 These clearance values also apply to guy insulators. 17 It is presumed that a flag or banner is fully extended but that there is no deflection or displacement of the flagpole or other supporting structure due to wind and that the conductors, cables, or rigid live parts are not displaced by the wind. The specified clearance is measured to the point of maximum displacement of the banner or flag towards the overhead utility facility. 18 When designing a line to accommodate oversized vehicles, these clearance values shall be increased by the difference between the known height of the oversized vehicle and 4.3 m.
28
NESC Errata
®
®
Pages 134, 135, and 136: There is an error in Table 234-1 (ft). The cell in column 6 of the header row should contain ―ungrounded equipment cases, 750 V to 22 kV.‖
NESC Errata
®
Page 137: There is an error in Footnote 11 that appears at the end of Table 234-1 (ft). The word ―215C5‖ should be replaced with ―215C4.‖ 11 The portion of anchor guys below the l owest insulator meeting Rules 279A1 and 215C4 may have the same cl earance as grounded guys.
Although Footnotes 12 and 13 were deleted from the previous version, the remaining footnotes should not have been renumbered. They should be listed as follows: 12 This footnote not used in this edi tion. 13 This footnote not used in this edi tion. 14 For cl earances above railings, walls, or parapets around balconies, decks, or roofs, use the clearances required for row 1b(1). For such clearances where an outside stairway exists to provide access to such balconies, decks, or roofs, use the clearances required for row 2b(2). 15 Does not include neutral conductors meeting Rule 230E1. 16 These clearance values also apply to guy insulators. 17 It is presumed that a flag or banner is full y extended but that there is no deflection or displacement of the flagpole or other supporting structure due to wind and that the conductors, cables, or rigid live parts are not displaced by the wi nd. The specified clearance is measured to the point of maximum displacement of the banner or flag towards the overhead utility facility. 18 When designing a line to accommodate oversized vehicles, these clearance values shall be increased by the difference between the known height of the oversized vehicle and 14 ft.
®
Page 138: There is a typographical error in Table 234-2 (m). The underscore should be removed from the comma in the last sentence of the parenthetical statement below the table caption.
Table 234-2— Clearance of wires, conductors, cables, and unguarded rigid live parts from bridges (Voltages are phase to ground for effectively grounded circuits and those other circuits where all ground faults are cleared by promptly de-energizing the faulted section, both initially and following subsequent breaker operations. See the definitions section for voltages of other systems. Clearances are with no wind displacement except where stated in the footnotes below. See Rules 234A, 234D1a, and 234H4.)
NESC Errata
®
Page 166: There is an error in Table 235-6 (mm). The cell in column 2 of row 2c should read ―75‖ and not ―3.‖
Page 142: There is an error in Footnote 2 that appears at the end of Table 234-3 (m). The word ―215C5‖ should be replaced with ―215C4.‖ 2 The portion of anchor guys below the lowest insulator meeting Rules 279A1 and 215C4 may have the same clearance as grounded guys.
Page 143: There is an error in Footnote 2 that appears at the end of Table 234-3 (ft). The word ―215C5‖ should be replaced with ―215C4.‖ 2 The portion of anchor guys below the lowest insulator meeting Rules 279A1 and 215C4 may have the same clearance as grounded guys.
NESC Errata
®
®
NESC Errata
®
®
NESC Errata
®
®
®
Page 222: There is a typographical error in Footnote 3 that appears at the end of Table 261-1. Delete the strikethrough (―R‖) in the last sentence of the footnote. 3 Wood and reinforced structures shall be replaced or rehabilitated when deterioration reduces the structure strength to 3/4 of that required when installed. When new or changed facilities modify loads on existing structures, the required strength shall be based on the revised loadings. If a structure or component is replaced, it shall meet the strength required by Table 261-1. If a structure or component is rehabilitated, the rehabilitated portions of the structures shall have strength greater than 3/4 of that required when installed.
29
NESC Errata
®
NESC Changes
®
®
®
Page 230: There is an error in Rule 279A2b(1). The sentence should contain ―215C4 or.‖ (1) The guy is otherwise insulated to meet the requirements of Rules 215C4 or 215C5 and 279A1.
Page 262: There is a typographical error in Rule 410A3b. The exception and notes are applicable to Rule 410A3 and not Rule 410A3b.
•Online at; http://standards.ieee.org/about/nesc/erp/index.html
NESC Schedule
®
®
•The NESC is revised every 5 years •NESC-2017 schedule –July 15, 2013- Final date to receive change proposals –September- October 2013- Committees meet and consider change proposals –September 2014- Proposed amendments printed. Comment period opens. –May 2015- Committee study period and comments- Comments due
•NESC-2017 schedule –October 2015- Committees prepare final report –January 2016- Proposed revision of NESC to NESC committee for letter ballot. –May 2016- Committee approved revisions submitted to ANSI for recognition as an ANSI standard –August 2016- Publication of the 2017 Edition of the NESC
References
®
®
®
-
-
-
NESC Schedule
®
®
NESC 2012 Presentation, Jim Tomaseski NESC 2012 Presentation, John Pierson Jr, Tim Weir, Betty Jo Kiesow NESC 2012 Presentation, Pamela (Pam) T. Tompkins, OSHA, Line Contractors strategic Partnership- IEEE report Hugh Hoagland- Arc Wear OSHA NFPA 70e Salisbury Protective Products Testing update on protective clothing and equipment for electric arc exposure, IEEE HD Electric Arc Flash Phenomena- Collaborative Research Project- IEEE Synergetic Design Brent McKinney- NESC- APPA Subcommittee member Arcing Flash/blast review with safety suggestions for design and maintenance, Tim Crnko, Steve Dyrnes 516-2009 - IEEE Guide for Maintenance Methods on Energized Power Lines
Evaluations
Please complete your evaluations. Please ensure that your name on your certificate appears as it does on your State PE license and that your licenses number is correct before you leave. Most importantly, please share this information with your fellow workers and always look for a safer way to perform every task – both work, home and in-between.
30
