Environmentally friendly, low cost HV/MV distribution substations using new compact HV and MV equipment

The paper presents a new standardized design for environmentally friendly, low cost HV/MV distribution substations. The new design, adopted by ENEL Distribuzione in Italy, is based on the following concepts, which are discussed in the paper: (i) use of a simplified single-line diagram and lay-out, (ii) use of new equipment types, (iii) very simple and compact design, and (iv) almost complete prefabrication. The paper firstly describes the new model applied by ENEL Distribuzione for the development of the MV networks, which enables use-and takes advantage of-the new type of compact HV/MV substations. Typical applicable simplified substation single-line diagrams are reviewed and justification is given of the selected diagram. The relevant implementation is presented for: (i) the air-SF/sub 6/ (hybrid) insulated 170 kV switchgear; (ii) the new 24 kV metal enclosed air insulated switchgear, which is housed in a container and is very compact due to the use of circuit breakers withdrawable with vertical movement. The authors believe that the new largely prefabricated HV/MV substation will contribute much to improve the MV network topology, uprate the power capability and facilitate the extension of distribution networks, improve quality of service to consumers and substantially reduce the operation costs.