The Common Electric Power Transmission System Model (CTM) is an intuitive, extensible, language-agnostic, and range-validating specification of electric power network components’ parameter names and units, and the relation between components, intended for use by the research community developing new computational methods for power systems operations and simulation. This repository specifies CTM as a JSON Schema, provides documentation, derivates (code-generated) implementations of CTM, and example data and usage of the schema for important use cases.