On August 1, the 2017 edition of the National Electrical Safety Code (NESC) was released. This latest edition includes a number of changes and exceptions to rules, as well as the introduction of some new tools to help users more easily access and utilize NESC content. Below NESC Chairman Nelson Bingel summarizes several of the changes:
Rules 092C1 and 096C
Exceptions were added to allow less than the four-grounds-in-each-mile requirement under specific limiting conditions.
Revisions were made to address safety sign locations, adjoining fence restrictions, and impenetrable fence modifications.
Revised to require Electrical Supply Station clearance values in Tables 124-1 and 110-1 to have appropriate atmospheric correction factors applied for altitudes above 1000m (3300 feet).
Guy insulator rules were rewritten and consolidated for easier reading. A major change redefines the 8-foot clearance required if the anchor guy breaks, rather than breaks below the lowest guy insulator.
Vegetation management should now be performed around supply and communication lines, not just supply lines.
Clearances over swimming pools now apply to permanent above-ground pools with and without attached decks.
All rules associated with clearances of antennas were consolidated into one rule.
Increased the vertical clearance between luminaries that are not effectively grounded and communication cables and equipment from 20 inches to 40 inches.
Rule 250C - Extreme Wind Loading
Replaced references for extreme wind map from ASCE-7-05 to ASCE-74-10.
Rule 261H1b - Tensions
A requirement was added to consider Aeolian vibration and mitigation methods. Aeolian vibration is low amplitude, high frequency vibration that is most common on transmission lines, and causes damage to conductor strands at suspension clamps and other attachment points. There are multiple ways specified in the rule to mitigate this potential, but if limiting tension is the only option, limits are specified as a percent of ultimate conductor capacities.
Insulator allowable strength percentages were adjusted to coincide with manufacturers' current rating practices. In addition, classifications for distribution and transmission insulators were created and separate allowable strength percentages were established for Rule 250B loading compared to Rule 250C & D loading.
An exception was added to allow greater spacing of grounding points under specific limiting conditions.
Revised to include new requirements and exceptions for protecting workers with arc-rated clothing and equipment.
Revised to include new requirements for the use of fall protection equipment.
New NESC App, Handbook & Tabs
Something completely new and useful for the latest NESC edition is the introduction of the NESC 2017 mobile app, which will be available for iOS, Android, and Windows, providing easy access to the code. For those in the field, the new App is a handy and comprehensive reference source that includes all of the content of the printed code with enhanced features, including:
Another important and useful item for this new NESC edition is the expanded and reformatted 2017 NESC Handbook, Premier Edition. This book now includes a representation of the NESC code language along with commentary by contributors, and represents a next-generation tool for professionals wanting to improve their understanding of the NESC. Following each section of the NESC text, the handbook gives users insight into a history of the NESC's rules; how the rules might be applied; interpretations; background interspersed and coincident with the represented portions of code being discussed and highlighted; and responses to change proposals during the past 90 years.
Also included in the ancillary items are the first set of NESC Tabs, 48 durable, self-adhesive tabs that are compatible with both the NESC 2017 Edition and 2017 NESC Handbook. The tabs are color-coded to make locating important information fast and easy. The set includes easy-to-affix pre-printed press-and-stick tabs and blanks for individual notations.
The IEEE Standards Association will host an informational workshop in San Antonio, Texas on October 18-19. This workshop will include a review of the changes in all sections of the code. There will also be presentations on distributed energy resources, resiliency, microgrids, interconnection, and an NESC/NEC whitepaper. You can learn more about that event here.
Online Learning Opportunities
IEEE will be offering a series of new educational courses online, also known as MOOCS (massive open online courses) on the NESC 2017 Edition. These include:
About the Author
Nelson Bingel has 30 years of industry experience focused around structural issues related to overhead lines. He received a BSME degree from Purdue University and has served on the NESC committee for 25 years. Nelson became Chairman of the NESC Main Committee in 2016. He also participates on several IEEE technical committees for overhead lines and is Chairman of the ASC O5 committee which develops specifications for new wood poles. In his current role at Osmose as Vice President - Product Development and Integration, Nelson overseas research and development of improved structure inspection processes, preservatives and restoration systems.