An electrical technical specialist for Spectra Energy, Scott Carroll works with 22 electrical technicians, covers 57 natural gas compressor stations, and focuses on installation, maintenance, testing, and project management of electric power distribution equipment and systems. One day, while one of his technicians was performing his daily maintenance and troubleshooting tasks, the maintenance team learned firsthand the importance of having phase barriers in place on medium-voltage motor control centers (MCCs).
As you will see in this photo essay, the author and his technician tracked down the culprit behind an arc flash incident in one of his facility’s newer MCCs that cost the company $500,000. Following some investigation and analysis, he discovered that — due to the fact that there were no phase barriers in place on a motor contactor — a field mouse had entered the MCC and come into contact with a section of the bus that connected the fuses and the contactor, ultimately prompting the arc flash. At this point, he immediately contacted the equipment manufacturer and purchased the materials necessary to complete repairs from the arc flash incident. During his conversation with the manufacturer’s representative, the author learned that phase barriers can be installed with the new replacement contactor and prevent this type of incident in the future. The incident cost Spectra Energy $125,000 in materials and labor — a hefty price to pay when the phase barriers could have been installed during manufacturing for approximately $75 each. Note: While conducting research on this subject, the author learned that several manufacturers do not install phase barriers on this type of equipment from the factory but can be purchased as an option.
Later on, while performing annual maintenance on similar MCCs in the company’s system, he found the same situation (i.e., lack of phase barriers). Using the data he’d gathered previously, Carroll was able to convince station supervisors to allow their technicians to purchase and install similar phase barriers — a proactive step that will avoid similar arc flash incidents from occurring at these sites.
