scope:

Introduction

NEMA has long recognized that equipment short circuit current ratings and interrupting ratings are determined by the engineer or contractor after understanding the available fault currents to which they will be subjected. Utilities have longstanding practices to provide a conservatively high maximum level of available fault current based on their current and future power generation equipment, transmission, and distribution systems required to support their customers' electrical power demands. Once again, NEMA recognizes that this has been an accepted industry practice that ensures equipment is appropriately rated to control electrical energy safely. However, the introduction of arc flash protection in NFPA 70E, Electrical Standard for Safety in the Workplace, is changing industry needs to ensure a safe maintenance environment beyond safe operation of the equipment.