This part of IEC62271 specifies the service conditions, rated characteristics, general structural requirements and test methods of the assemblies of the main electrical functional units of a high-voltage/low-voltage distribution substation, duly interconnected, for alternating current of rated operating voltages above 1kV and up to and including 52kV on the high-voltage side, service frequency 50Hz or 60Hz. This assembly is to be cable-connected to the network, and intended for installation within an indoor or outdoor closed electrical operating area. A Compact Equipment Assembly for Distribution Substation (CEADS) as defined in this document is designed and tested to be a single product with a single serial number and one set of documentation. The functions of a CEADS are: switching and control for the operation of the high-voltage circuit(s); protection of the high-voltage/low-voltage transformer functional unit; high-voltage/low-voltage transformation; switching and control for the operation and protection of the low-voltage feeders. However relevant provisions of this document are also applicable to designs where not all of these functions exist (e.g. equipment comprising only high-voltage/low-voltage transformation and switching and control for the operation and protection of the low-voltage feeder functions or equipment without switching and control for the operation of the high-voltage circuit(s)). NOTE For the purpose of this document a self-protected transformer is considered not as a CEADS, but as a functional unit, designed and type tested to its own product standard IEC60076‑13:2006 .