Medium-voltage substations

A medium-voltage substation is a structure located at a network node, housing a range of equipment designed to protect the network and facilitate operation. The majority of medium-voltage networks are now built using underground cables, which means that the only possible operating interventions can only be carried out from the substations, hence the growing importance of these structures. Increasingly, medium-voltage substations are home to equipment that provides the new functions needed for better-controlled, even automated, operation.

This article deals only with three-phase alternating current installations. In the text, the terms high voltage and medium voltage, used in everyday language, are employed. On the other hand, the abbreviations are those defined in the technical decree of April 2, 1991, namely HTB for voltages above 50 kV (high voltage) and HTA for voltages between 1 and 50 kV (medium voltage).

The article is aimed at :

• designers, installers and operators of public or private substations;

• Electrical engineering technicians and engineers.

It describes the functionalities of substations encountered on HVA networks, terminology and standards, economic aspects, requirements and constraints formalized in specifications, structures and diagrams of public distribution substations, structures and diagrams of private substations and the technique and construction of HVA substations.