Arc flash hazard in distribution systems protected with fuses: IEC vs. IEEE approach

摘要

Medium- and low-voltage electrical utility distribution systems in major Italian cities (e.g. Torino, Milano, etc.) widely employs fuses as protective devices. The excellent ratio efficiency to costs of fuses amply justify their adoption. However, European and International standards do not include provisions for the calculation of arc flash incident energies, as well as for the selection of appropriate personal protective equipment. This paper seeks to clarify the arc flash hazard posed by clearing times of fuses installed on the primary side of substations, when they are called to clear faults on the low-side of the transformer. A case study detailing the consequences of an accident involving a fault in a low-voltage distribution switchboard of a utility substation is presented. An analysis of the electrical safety criteria present in National and International Standards and Guides is performed; possible improvements of the safety of workers by including arc flash protection criteria per IEEE standard are also discussed.