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245 and 305 Overcurrent Protection – Systems Over 1000V ac/1500V dc

Revision/New

Leviton Comment: We combined these two articles here because they both relate to the same area.

Change Summary

  • Back in the 1920 NEC the voltage threshold increased from 550 volts to 600 volts. Then in 2017 the NEC included content addressing thresholds to 1000 volts. Today electrical technology is expanding quickly with technologies like photovoltaics and others. The NEC is keeping up and this article is an example.

NEC®Text

Article 245 Overcurrent Protection for Systems Rated Over 1000 Volts ac, 1500 Volts dc.
245.1 Scope.
245.2 Reconditioned Equipment.
245.21 Circuit-Interrupting Devices.
245.26 Feeders and Branch Circuits.
245.27 Additional Requirements for Feeders.

Article 305 General Requirements for Wiring Methods and Materials for Systems Rated Over 1000 Volts ac,
1500 Volts dc, Nominal
305.1 Scope.
305.3 Other Articles.
305.4 Conductors of Different Systems.
305.5 Conductor Bending Radius.
305.6 Protection Against Induction Heating.
305.7 Covers Required.
305.8 Raceways in Wet Locations Above Grade.
305.9 Braid-Covered Insulated Conductors - Exposed Installation.
305.10 Insulation Shielding.
305.11 Moisture or Mechanical Protection for Metal- Sheathed Cables.
305.12 Danger Signs.
305.15 Underground Installations.

Material taken from the National Electric Code. is reprinted with permission from NFPA 70., 2023 edition. National Electrical Code®, Copyright 2022, National Fire Protection Association, Quincy, MA. All rights reserved.

Expert Analysis

New articles have been added to address the requirements for overcurrent protection for systems rated over 1000 volts ac, 1500 volts dc.

Many consider these voltage levels as medium voltage (MV) and these articles provide guidance to the electrical industry, including inspectors, with more guidance in terms of medium voltage installations.

Figure 1

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