Article

In this article, Electrical Engineer, Jim Orosz, P.E. discusses the various ways that the National Electrical Safety Code (NESC) prescribes the placement of electrical lines and equipment to help safeguard the general public.

Electrical Equipment Safety

When the public comes into contact with electric supply lines or associated equipment, the results usually include electrical burns, shock injuries, and/or death. The National Electrical Safety Code (NESC) establishes standards for utility owned lines and equipment designed to prevent these incidents from occurring. In simplified form, the NESC sets out to:

  • Position overhead lines at prescribed heights
  • Bury underground lines at prescribed depths
  • Prohibit access to equipment at ground level

The electrical engineers at Robson Forensic have been retained on behalf of both plaintiffs and defendants to investigate cases involving exposure to electric utilities. This document provides basic information on the NESC standards relevant to public safety. Please contact our experts directly to discuss your case and how Robson Forensic can assist.


The National Electrical Safety Code

The National Electrical Safety Code (NESC) stipulates how the public must be protected from exposure to electric supply lines and equipment. “Systems and equipment operated by utilities, or similar systems and equipment, of an industrial establishment or complex under the control of qualified persons” fall under the NESC. The NESC covers basic provisions for safeguarding of persons from hazards arising from the installation, operation, or maintenance of:

  1. conductors and equipment in electric supply stations, and
  2. overhead and underground electric supply and communication lines.

The NESC requirements have changed over the years. The date of construction in your case is useful for determining the relevant edition. Robson Forensic maintains NESC standards dating back to 1914 in its extensive technical library.

Guarding Ground Level Equipment

Rooms and spaces in which supply conductors or equipment are installed shall be so arranged with fences, screens, partitions, or walls to form an enclosure as to limit the likelihood of entrance of unauthorized persons or interference by them with equipment inside.

  • Entrances not under observation of an authorized attendant shall be kept locked.
  • A safety sign shall be displayed at each entrance. For fenced electric supply stations, a safety sign shall be displayed on each side of the fenced enclosure.
  • Metal fences, when used to enclose electric supply stations having energized electric conductors or equipment, shall have a height not less than 2.13 m (7 ft) overall and shall be grounded in accordance with Section 9.

Overhead Clearance Requirements

The NESC establishes standards for minimum safe distances between overhead power lines and structures. Safe distances vary depending on line voltage, type and purpose of structure, along with other circumstances. Below we have included information on the range of minimum clearance distances per current (2012) NESC standards based on circuits with less than 22kv. Please contact our experts for help determining the requirements specific to your case.

  • Buildings (horizontal clearance)
    • 4’6” – 7’6” - To walls and projections; unguarded windows; balconies; areas accessible to pedestrians
  • Buildings (vertical clearance)

    • 3’ – 12’6” - Over and under roofs or projections not accessible to pedestrians
    • 10’6” – 13’6” - Over or under balconies and roofs accessible to pedestrians
    • 10’6” – 18’6” - Over roofs accessible to vehicles
  • Installations (Signs; billboards; chimneys; radio and TV antennas; tanks; and other installations not classified as bridges or buildings)

    • 3’ – 7’ – Horizontal & vertical clearance

Underground Clearance Requirements

The NESC establishes standards for minimum depth of burial for electric supply lines. These standards are developed to protect buried cables from damage caused by expected surface usage as well as protecting the public from exposure to buried lines.

  • Minimum depths of burial typically range from 24” to 42” dependent upon line voltage
  • Cables should be installed in as straight and direct a line as practical.

 

Featured Expert

James M. Orosz, P.E.

As a Major in the U.S. Army Reserve, working with FEMA on disaster relief, a West Point graduate in electrical engineering, and an accomplished Professional Engineer in the private sector, Jim is uniquely qualified to investigate electrical safety matters.

For more than ten years Jim worked in engineering and engineering management positions with Consolidated Edison Incorporated. During this time he was responsible for the safety and reliability of the electrical power distribution system, which included conducting inspections of the distribution system, development of test specifications for underground cables, and managing maintenance on the network.