Everyone in the electrical industry, including the electrical apprentice, the journeyman, the master electrician, electrical contractor, electrical engineer, designer, the electrical inspector, et al., seem to use the phrase “neutral conductor.” However, until the 2008 National Electrical Code (NEC), we did not actually have a definition of a neutral. In the process of determining the definition of a neutral for the 2008 NEC, the NEC Technical Committee Task Group on the Definition of “Neutral Conductor” realized two definitions were required to adequately define this seemingly elusive component of the electrical system.
The definition of a neutral conductor, as developed by the task group, was derived from the International Electrotechnical Commission definition of neutral conductor with some minor text changes to adapt to the NEC style. This definition read, “Neutral Conductor—The conductor connected to the neutral point of a system that is intended to carry current under normal conditions.”
The definition establishes that any conductor connected to a neutral point of an electrical system is intended to carry current under normal conditions. Any electricians who find themselves connected to a neutral conductor carrying the imbalanced current of the circuit will certainly verify that the neutral is a current-carrying conductor. Most electricians, myself included, also will admit that it is very difficult to “get off” the neutral conductor once connected to it since the current is on the load side of the circuit. Most people either fall away, breaking the connection if on ground or floor level, or fall off the ladder when not working at grade level. We all count ourselves very lucky to have survived the neutral “connection.”
Whenever possible, work on the circuit in an electrically safe work condition. In other words, ensure the circuit has been locked off, and verify that the circuit is de-energized.
Upon analyzing the newly developed definition of a “neutral,” the task group then decided that a second definition was necessary to further explain the “neutral point.” The definition of neutral point was found in the IEEE Standard C57.12.80-2002 and read, “The common point on a wye-connection in a polyphase system or midpoint on a
single-phase, 3-wire system, or midpoint of a single-phase portion of a 3-phase delta system, or a midpoint of a 3-wire, direct-current system.” Again, with some minor text changes to fit the NEC format, this text was adopted into the 2008 NEC. To make the two definitions as technically correct as possible, a Fine Print Note was added to explain that the neutral point of the system is “the vectorial sum of the nominal voltages from all other phases within the system that utilize the neutral, with respect to the neutral point, is zero potential.” With the combination of the two definitions and the Fine Print Note, we finally have defined a neutral conductor.
Once the two definitions and the Fine Print Note were developed and fine tuned, the task group proceeded to comb the entire NEC for any reference to a grounded conductor where that conductor was not simply grounded but could or did act as a neutral conductor. This was a huge task since proposals then were written for each change that must occur within the NEC, and each individual NEC panel analyzed these proposed changes to ensure they agreed with the change from “grounded conductor” to “neutral conductor.” It was a job very well done.
The neutral conductor is the common point in the system where the three- phase conductors of a wye system are connected to the grounding-electrode conductor and the grounding electrode. It still is the common point in a 120/240-volt, single-phase, three-wire system grounded to the grounding electrode system at the midpoint between the two transformers or the midpoint of one of the transformers of a three-phase 120/240-volt delta high leg system. It also is the midpoint connection of a three-wire direct current system. All of us can verify that these midpoint connections ultimately will be the current-carrying point back for all of those “neutral conductors” that we know so well as the white or gray conductor current path of an unbalanced circuit.
What do not fit the definitions are installations with one hot conductor and a return conductor, such as may be found in a 120-volt single phase, two-wire system. Sections 250.20(B)(1) and 250.26(1) still require the grounding-electrode connection, and 200.6 still requires the conductor to be white or gray “neutral” conductor. However, it is not a neutral conductor, even though many people still refer to it as a neutral. This is a grounded conductor, but be careful. It is just as lethal, if not more so than our “neutral” conductor.
ODE is a staff engineering associate at Underwriters Laboratories Inc., in Research Triangle Park, N.C. He can be reached at 919.549.1726 or at firstname.lastname@example.org.