Engineering glossary, plain English.
Reference definitions for the terminology we use every day. Linked to deeper explainers where available.
AHJ — Authority Having Jurisdiction
The local regulator responsible for approving electrical installations. In the US, typically a city or county building department. In solar permitting, the AHJ defines local plan-check requirements, submission format, and inspection process. Each AHJ has quirks; a good permit vendor maintains checklists per jurisdiction.
Arc Flash
The intense heat, light, and pressure wave generated when an electrical fault creates an arcing short-circuit. Arc flash hazards are quantified via IEEE 1584 incident-energy calculations and mitigated through NFPA 70E-compliant PPE selection, approach boundaries, and work practices. See our NFPA 70E guide.
BEP — BIM Execution Plan
A document defining how a project's BIM will be executed: LOD requirements, coordinate system, file naming, model federation, clash detection process, deliverable schedule. Required input for any outsourced BIM engagement.
BIM — Building Information Modeling
An intelligent 3D modeling workflow where model elements carry metadata beyond geometry (equipment tags, specs, manufacturer data). Enables coordination, clash detection, and digital twins. Typical tools: Revit, Navisworks.
IEEE 1584
The industry-standard method for calculating arc flash incident energy. IEEE 1584 output drives NFPA 70E-compliant PPE selection and equipment label values. Performed in ETAP, SKM Power Tools, or similar; requires accurate upstream fault data and protection settings.
Incident Energy
The thermal energy density (typically in cal/cm²) delivered to a worker at the working distance during an arc flash event. Calculated via IEEE 1584, used to determine PPE category and arc flash boundary per NFPA 70E.
LOD — Level of Development
BIM concept defining how developed a model element is at a given project phase. Common levels: LOD 100 (conceptual), 200 (approximate geometry), 300 (accurate geometry), 350 (coordinated with other disciplines), 400 (fabrication-ready). Defined in the project's BEP.
MCC — Motor Control Center
A grouped assembly of motor starters, protective devices, and associated wiring in a single enclosure for controlling multiple motors from a common bus. MCC documentation is a core electrical drafting deliverable for industrial and mining facilities.
MEP
Mechanical, Electrical, Plumbing. The three technical disciplines that share coordination responsibility on most commercial and industrial building projects. In BIM terms, the three disciplines that drive the most clashes.
NEC — National Electrical Code
NFPA 70. US foundational code governing the installation of electrical systems. Revised every three years (current: NEC 2023). Adopted into law by states and local AHJs.
NFPA 70E
US consensus standard for electrical safety in the workplace. Addresses worker protection from shock, arc flash, and arc blast through risk assessment, safe work practices, PPE, and training. Referenced by OSHA as industry best practice. Full guide.
SLD — Single-Line Diagram
A simplified electrical schematic representing a three-phase power system as a single line, showing sources, transformers, protective devices, buses, and loads with their ratings. The master reference document for any electrical system. Full guide.
Substation
An assembly of electrical equipment for voltage transformation, switching, or protection. Transmission substations typically operate at 66 kV and above; distribution substations step down to 11 kV or lower for local distribution.
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