Standard Method for Remediation of Short Circuit Failures of Protective Devices
Due to the number of assumptions and possible solutions, the method detailed here attempts to find the cheapest and least intrusive method of addressing underrated protective devices that has failed short circuit. The typical solution for under-rated protective devices is replacement. Series ratings should be checked before simply replacing protective devices. The purpose of this method is to ensure that the most effective solution is found for all failed equipment and can be completed even if the person doing it is not a subject matter expert. 1. Validate the short circuit rating with manufacturers The first step is to verify that the short circuit rating listed or assumed is accurate for all failed equipment. Assumptions are often made on equipment that does not have a short circuit rating listed. It is also not uncommon even on equipment with a listed short circuit rating to have variation depending on installation or to have unlabeled series ratings that were applied. Verifying the short circuit rating is best done by reviewing the datasheet or sending the nameplate information to the manufacturer. 2. Identify possible breakers/fuses that will pass short circuit While there are plenty of options for different short circuit ratings of protective devices, there are also plenty of different physical sizes of devices. It is considered best practice to stay within the manufacturer as well. For instance, if you have a Square D panel, it would be best to use Square D breakers. Reaching out to the manufacturer/vendors will also help identify which breakers will both physically fit in the equipment, as well as achieve the desired short circuit rating. 3. Ensure that proposed breaker/fuse will not negatively impact the arc flash results We must also consider the impact of the proposed breaker or fuse on the arc flash results. Because different breakers and fuses have different trip characteristics, an engineering analysis must be run to ensure the equipment downstream of the new protective device has as low of an incident energy level as possible.
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