The $125,000 field mouse

Equipment design and installation can account for a major arc flash incident. Having the correct phase barriers in place to shield fuses, contactors, buswork, etc... can save you time and money. This paper discusses an incident our company had involving the installation of a new Medium Voltage Motor Control Center (MCC). There were no phase barriers installed between the section of bus that connects the fuses and the contactor. The result was an arc flash incident when a rodent entered the MCC and came into contact with these connections. During the repairs we contacted the manufacturer of the equipment and purchased the phase barriers for the new contactor and installed them. This paper also shows how we found a similar problem while performing routine yearly maintenance on a similar Medium Voltage MCC at a different location within our system. We have since ordered the phase barriers for this facility as well. While doing research I have found that these phase barriers are not installed on several different manufacturers of this type of equipment. With proper engineering and installation techniques, these arc flash incidents can be avoided.