A global auto manufacturer was expanding its USA manufacturing plant to begin building a new model. One of the goals of the expansion was to design a state-of-the-art power system—one that provided redundant power and maximized safety for the plant’s personnel.
The most dangerous activity at the plant is the annual power system maintenance, which includes opening and closing circuit breakers and other tests. To keep the plant operational, personnel perform these tasks on energized circuits, which presents a potential arc-flash safety hazard. The danger is heightened because this task is only performed once a year, and less familiar tasks pose an increased risk of human error.
After evaluating multiple power system designs, the manufacturer chose an innovative SEL arc-flash protection scheme. This design, which includes an SEL-3555 Real-Time Automation Controller (RTAC) and SEL-751A Feeder Protection Relays, uses light sensors and fast overcurrent detection to trip breakers in less than 10 milliseconds. Because the system operates so fast, it significantly limits arc-flash incident energy and protects personnel and equipment from arc blasts. The addition of the RTAC enabled the use of fiber-optic communications, which significantly reduced the amount of wiring and provided greater system visibility and performance.
Additionally, the design provides full redundancy for every major piece of equipment in the protection scheme, which ensures power availability throughout the plant. You can find further technical details in the case study “Safer by Design: Protecting Industrial Personnel and Equipment From Arc-Flash Hazards.”
An arc flash is a type of electrical explosion that can expel large amounts of energy and molten metal. With temperatures exceeding 35,000°F (19,426°C), the arc blast from an arc-flash event can result in severe equipment damage and fatalities. Arc-flash events are often triggered by accidental contact with energized conductors (e.g., dropped tools or intruding rodents).
A fast protection system is critical to effectively mitigate an arc-flash event. The faster the system can detect an event and shut off the power, the less arc-flash energy is produced and the lower the risk is to personnel and equipment.
The SEL solution significantly improved safety by reducing the arc-flash hazard risk at the new facility. The solution also allows engineers to perform maintenance remotely, which helps them to work at a safe distance from any potential arc-flash events.
According to the facilities engineer on the project, the SEL protection scheme provides reliable power and helps protect their personnel and equipment. As a result, the manufacturer recently completed retrofitting the original plant’s power system with the same SEL equipment.
This is the safest medium-voltage switchgear in any [of our facilities] in the world.