Electrical engineer Eldo C. Koenig operating an AC network analyzer¹ analog computer² he designed at the Electrical Department of the Allis-Chalmers Manufacturing Company 1951.
From 1929 to the late 1960s, large alternating current power systems³ were modelled and studied on AC network analyzers or transient network analyzers. They were also called alternating current network calculators or AC calculating boards. These special-purpose analog computers were an outgrowth of the DC calculating boards used in the very earliest power system analysis. Using resistors and capacitors, AC network analyzers were much used for power-flow studies, short circuit calculations, and system stability studies, but were ultimately replaced by numerical solutions⁴ running on digital computers.
Eventually powerful digital computers replaced analog network analyzers for practical calculations, but analog physical models for studying electrical transients⁵ are still in use.
https://en.wikipedia.org/wiki/Network_analyzer_(AC_power)
https://en.wikipedia.org/wiki/Analog_computer
https://en.wikipedia.org/wiki/Electric_power_system
https://en.wikipedia.org/wiki/Numerical_analysis
https://en.wikipedia.org/wiki/Voltage_spike