Code Change Summary: New definitions in Article 100 for Line-to-Ground, Line-to-Line, Line-to-Neutral.

SME commentary: The 2026 NEC^® introduces three new definitions into Article 100 to provide clarity for the commonly used phrases Line-to-Ground, Line-to-Line, and Line-to-Neutral. These additions aim to eliminate ambiguity surrounding how the word “line” is used throughout the Code, particularly in the context of voltage references and conductor relationships, regardless of whether the power system is AC or DC, grounded or ungrounded.

Why the Change Was Made:
In past editions of the NEC^®, the word “line” appeared in a variety of voltage-related requirements, but its meaning could shift depending on the context. Many users defaulted to thinking it referred to an ungrounded conductor or assumed it only applied to AC systems. However, with the rise in DC systems (photovoltaic systems, energy storage systems, and the like), there’s now a growing need for terms that apply universally, without the guesswork.

The code panel initially rejected the proposal, suggesting the terms were already well understood and better left to training manuals. However, through persistence and a well-supported public comment submitted during the second draft (this time on behalf of the Correlating Committee DC Task Group) the code panel was convinced. The second draft substantiation emphasized the need for clarity in both AC and DC contexts and highlighted how misinterpretation could lead to misapplication of requirements in safety-critical scenarios.

New Definitions:

Line-to-Ground
An electrical reference between a current-carrying conductor other than a neutral conductor and an equipment grounding conductor, grounded equipment, or ground.

Line-to-Line
An electrical reference between two current-carrying conductors in a circuit other than a neutral conductor.

Line-to-Neutral
An electrical reference between a current-carrying conductor, other than a neutral conductor, and a neutral conductor or neutral point in a circuit.

Why it Matters

These definitions may seem minor at first glance, but they have far-reaching implications. They create a shared language across all supply system types, AC or DC, grounded or ungrounded. That means less confusion in design, installation, inspection, and enforcement, making for safer, more reliable systems.

Below is a preview of the NEC^®. See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2026 NEC^® edition of NFPA 70.

2023 Code Language:

Article 100 Definitions.

These definitions did not exist.

2026 Code Language:

Article 100 Definitions.

N Line-to-Ground. An electrical reference between a current-carrying conductor other than a neutral conductor and an equipment grounding conductor, grounded equipment, or ground.

N Line-to-Line. An electrical reference between two current-carrying conductors in a circuit other than a neutral conductor.

N Line-to-Neutral. An electrical reference between a current-carrying conductor, other than a neutral conductor, and a neutral conductor or neutral point in a circuit.