Edith Clarke: Architect of Modern Power Distribution

Edith Clarke was a powerhouse in practically every sense of the word. From the start of her career at General Electric in 1922, she was determined to develop stable, more reliable power grids.

And Clarke succeeded, playing a critical role in the rapid expansion of the North American electric grid during the 1920s and ’30s.

During her first years at GE she invented what came to be known as the Clarke calculator. The slide rule let engineers solve equations involving electric current, voltage, and impedance 10 times faster than by hand.

Her calculator and the power distribution methods she developed paved the way for modern grids. She also worked on hydroelectric power plant designs, according to a 2022 profile in Hydro Review.

She broke down barriers during her life. In 1919 she became the first woman to earn a master’s degree in electrical engineering from MIT. Three years later, she became the first woman in the United States to work as an electrical engineer.

Her life is chronicled in Edith Clarke: Trailblazer in Electrical Engineering. Written by Paul Lief Rosengren, the book is part of IEEE-USA’s Famous Women Engineers in History series.

Becoming the first female electrical engineer

Clarke was born in 1883 in the small farming community of Ellicott City, Md. At the time, few women attended college, and those who did tended to be barred from taking engineering classes. She was orphaned at 12, according to Sandy Levins’s Wednesday’s Women website. After high school, Clarke used a small inheritance from her parents to attend Vassar, a women’s college in Poughkeepsie, N.Y., where she earned a bachelor’s degree in mathematics and astronomy in 1908. Those degrees were the closest equivalents to an engineering degree available to Vassar students at the time.

In 1912 Clarke was hired by AT&T in New York City as a computing assistant. She worked on calculations for transmission lines and electric circuits. During the next few years, she developed a passion for power engineering. She enrolled at MIT in 1918 to further her career, according to her Engineering and Technology History Wiki biography.

After graduating, though, she had a tough time finding a job in the man-dominated field. After months of applying with no luck, she landed a job at GE in Boston, where she did more or less the same work as she did in her previous role at AT&T, except now as a supervisor. Clarke led a team of computers—employees (mainly women) who performed long, tedious calculations by hand before computing machines became widely available.

The Clarke Calculator let engineers solve equations involving electric current, voltage, and impedance 10 times faster than by hand. Clarke was granted a U.S. patent for the slide rule in 1925.Science History Images/Alamy

While at GE she developed her calculator, eventually earning a patent for it in 1925.

In 1921 Clarke left GE to become a full-time physics professor at Constantinople Women’s College, in what is now Istanbul, according to a profile by the Edison Tech Center. But she returned to GE a year later when it offered her a salaried electrical engineering position in its Central Station Engineering department in Boston.

Although Clarke didn’t earn the same pay or enjoy the same prestige as her male colleagues, the new job launched her career.

According to Rosengren’s book, during Clarke’s time at GE, transmission lines were getting longer and larger power loads were increasing the chances of instability. Mathematical models for assessing grid reliability at the time were better suited to smaller systems.

To model systems and power behavior, Clarke created a technique using symmetrical components—a method of converting three-phase unbalanced systems into two sets of balanced phasors and a set of single-phase phasors. The method allowed engineers to analyze the reliability of larger systems.

Vivien Kellems [left] and Clarke, two of the first women to become a full voting member of the American Institute of Electrical Engineers, meeting for the first time in GE’s laboratories in Schenectady, N.Y. Bettmann/Getty Images

Clarke described the technique in “Steady-State Stability in Transmission Systems,” which was published in 1925 in A.I.E.E. Transactions, a journal of the American Institute of Electrical Engineers, one of IEEE’s predecessors. Clarke had scored another first: the first woman to have her work appear in the journal.

In the 1930s, Clarke designed the turbine system for the Hoover Dam, a hydroelectric power plant on the Colorado River between Nevada and Arizona. The electricity it produced was stored in massive GE generators. Clarke’s pioneering system later was installed in similar power plants throughout the western United States.

Clarke retired in 1945 and bought a farm in Maryland. She came out of retirement two years later and became the first female electrical engineering professor in the United States when she joined the University of Texas, Austin. She retired for good in 1956 and returned to Maryland, where she died in 1959.

First female IEEE Fellow

Clarke’s pioneering work earned her several recognitions never before bestowed on a woman. She was the first woman to become a full voting member of the AIEE and its first female Fellow, in 1948.

She received the 1954 Society of Women Engineers Achievement Award “in recognition of her many original contributions to stability theory and circuit analysis.” She was posthumously elected in 2015 to the National Inventors Hall of Fame.