Adding life and safety to existing substations

This paper will discuss a set of projects in a large US chemical manufacturing facility which lowered the arc flash incident energy at several 480-volt switchgear lineups and extended the life of the equipment through the installation of retrofit circuit breakers. After the arc flash hazard study was completed at the facility, it was found that many 480-volt, 1000 kVA substation switchgear lineups had incident energy levels well above safe working conditions. Additionally, with major unit outages approaching, it was desired to find a cost-effectively way to extend the life of the existing, 35-year old equipment. Through analysis and field trials it was determined that the upstream fuses could be replaced with a lower rating and significantly reduce the arc flash incident energy to within acceptable levels. Additionally, a retrofit circuit breaker was found which did not require any physical modifications to the switchgear and provided a new breaker in place of the old equipment. The advanced features of the new breaker trip unit allows personnel to activate an alternate trip setting which lowers the downstream arc flash incident energy on the motor control centers to minimal levels allowing less protective equipment when performing common energized tasks. Finally, with the addition of electrical control, personnel are able to operate the new breakers remotely outside of the arc flash hazard boundary.