Our History

Innovation is the heart of SEL.

In 1982, Edmund O. Schweitzer, III, invented the first microprocessor-based digital protective relay. The SEL-21 was the culmination of research done for Schweitzer’s doctoral thesis, and it ushered in a new era of power system protection and went on to revolutionize the electric power industry.

Schweitzer believed that the device would provide real value to electric utilities and their end-users so he founded Schweitzer Engineering Laboratories in the basement of his home in Pullman, Washington, and began working to bring his invention to market. He spent the next two years setting up manufacturing, business, and marketing processes, hiring a small group of employees, and working to teach the industry about the new technology and its benefits. In 1984, Schweitzer flew to Fergus Falls, Minnesota, to provide a demonstration of the SEL-21 at Otter Tail Power Company that resulted in the first sale for SEL.

The grit, creativity, and spirit of invention that helped propel Schweitzer and the first SEL employees from the basement to more than 100 locations around the globe continue to be a driving force and source of inspiration today as the team of more than 6,000 people work to fulfill the SEL mission to make electric power, safer, more reliable, and more economical.

Timeline of Events


Dr. Schweitzer launches Schweitzer Engineering Laboratories with the invention of the SEL-21, the first relay to use microprocessor-based computation and algorithms.


SEL makes its first sale to Otter Tail Power Company in Fergus Falls, Minnesota, as a company of seven working out of Dr. Schweitzer’s basement.


SEL grows to 100 employees.


SEL implements the employee stock ownership plan (ESOP).


We release the SEL-351, which becomes the benchmark for protective relay standards in North America.


SEL begins offering engineering consulting, testing, and design through our Engineering Services team.


We introduce our unprecedented ten-year, worldwide product warranty—the best in the industry.


SEL establishes Government Services to serve government customers.


SEL opens a site in Monterrey, Mexico, to manufacture high-quality panels for our customer Comisión Federal de Electricidad.


SEL acquires E. O. Schweitzer Manufacturing in Mundelein, Illinois, which was started by Dr. Schweitzer’s father, Edmund O. Schweitzer, Jr.


SEL becomes 100 percent employee-owned.


SEL opens a manufacturing facility in Lewiston, Idaho.


We introduce the SEL-T400L Time-Domain Line Protection, the fastest relay in the world.


SEL President and Chief Technology Officer Dr. Edmund O. Schweitzer, III, is inducted into the National Inventors Hall of Fame for his invention of the microprocessor-based digital protective relay.


We open the doors to our fifth manufacturing facility, in West Lafayette, Indiana. The site’s proximity to Purdue University allows close research collaboration between the two entities.


SEL opens a printed circuit board fabrication facility in Moscow, Idaho