A substation is used to adjust voltage and distribute electrical energy. The transformer (1) converts the electrical voltage between high, medium, or low voltage. The energy is fed to busbars (2), which serve as central distributors. Disconnectors (3) enable visible, voltage-free separation of system components, while circuit breakers (4) safely switch load and short-circuit currents on and off. Instrument transformers (5) measure current and voltage for protection and control technology. Surge arresters (7) are installed to protect against overvoltages, and earthing switches (8) ensure that de-energized parts of the system are safely earthed during maintenance work. The transition from the substation to the transmission grid is usually defined by the portal mast.
 Source: https://www.swissgrid.ch/de/home/operation/power-grid/technologies.html
A substation can be modeled completely as follows:
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