SEL was founded in Pullman, Washington, in 1982 when Dr. Edmund O. Schweitzer III invented and marketed the first all-
digital protective relay. Schweitzer created the relay as a Ph.D. project while at
Washington State University. He sold his first product, the SEL-21, to
Otter Tail Power Company in Fergus Falls, Minnesota, in 1984. Otter Tail initially used the SEL-21 for its fault location and event recording functions. SEL uses OTTER and TAIL as default passwords for their relays as an homage to their very first customer. In 1985, SEL built its first building and employed eleven people. In 2009, SEL became 100% employee-owned under an
employee stock ownership plan (ESOP). SEL has five manufacturing facilities in the U.S. located in Pullman, Washington; Moscow Idaho; Lewiston, Idaho; Lake Zurich, Illinois; and West Lafayette, Indiana. In 2003, the company opened its first Regional Integration Center in San Luis Potosí, followed by May 2017 opening in Saudi Arabia city of Dammam with a peak manufacturing ability for 1,200 control panels. With Mexico to build complete panels and PowerMAX for all of North America. The components for the panels are made in Pullman and shipped to Mexico, where they are integrated into panels.
E. O. Schweitzer Manufacturing, a manufacturer of fault indicators and sensors started by
Edmund O. Schweitzer, Jr. in 1949, became a division of SEL in 2005. ==Products==