240.67 Arc Energy reduction

240.67 Arc Energy Reduction

This section came into the NEC as part of the 2017 National Electrical Code changes.  It was prompted after the introduction of 240.87 as a natural progression.  Larger overcurrent devices have a more difficult time of reducing incident energy simply due to the time-current characteristic curve.

NEC 2017 Changes
This is the first time that an arc flash reduction requirement for fuses entered the NEC.  240.67 sprung out of the elevated awareness of incident energy on large OCPDs due to the continued developments in section 240.87 which focused on circuit breakers.  Any fuse 1200A and larger and that have a clearing time of greater than 0.07seconds at the arcing current will require an arc reduction technology.

NEC 2020 Changes
These are the changes made during the 2020 NEC code cycle to 240.67 which focuses on fuses. An emphasis on arcing currents and an emphasis on performance testing occurred this cycle.

Solutions to meet these requirements

Arc Flash Relay

Arc Flash Switch

Shunt Trip Switch

An arc fault is the most devastating type of fault in medium voltage (MV) and low voltage (LV) switchgear. If an arc fault occurs, the EAFR system reduces arc energy by quickly clearing the current feeding the arc

The arc energy reduction switch leverages this relay to provide both arc reduction and ground-fault protection of equipment.

The 1200A and above switch that meets this requirement must be equipped with shunt trip capabilities.  Eaton’s solution brings the most cost effective solution to the table to meet this requirement.  

Arc Energy Reduction

This video provides a deep discussion of incident energy calculations and digs into both 240.87 and 240.67 to help you understand how to meet the requirements of these sections of the NEC.