This document provides rules for structuring of systems in the domain of power supply systems, being supplementary to the general principles for the structuring of systems including structuring of information about systems specified in IEC 81346-1. Based on these principles, rules and guidance are given for the formulation of unambiguous reference designations for objects in any system. The reference designation identifies objects for the purpose of creation and retrieval of information about an object and, where realized, about its corresponding component. A reference designation labelled at a component is the key to finding information about that object among different kinds of documents. The principles are general and are applicable to all technical areas (e.g. mechanical engineering, electrical engineering, construction engineering, process engineering). They can be used for systems based on different technologies or for systems combining several technologies. This document also defines classes for systems and spaces in the field of power supply systems.