98-1 Companion Specification
Companion Specification for Electricitiy Metering; DLMS and HDLC via Telephone Networks
Interest has considerably grown in metering models and objects. The DLMS User Association is about to release object definitions to its members. The objects are a part of the COmpanion Specification for Electricity Metering COSEM. It is a complete set of specifications defining
- a library of metering objects,
- how the objects are mapped to DLMS data units,
- how the DLMS data units are transported over a specific channel
COSEM does not define new standards, it defines which standards are used and how they are used. COSEM conforms to the OSI model for open systems.
The application model is an object oriented approach to model the behaviour and the data of a meter as seen from the client (Master Station, HHU). It is a systematic approach to split the complex functionality of a meter into generic building blocks (objects). Examples of objects are: Register, Clock, Profile, Demand Register, ... The customised meter is built by choosing the appropriate building blocks from the object library.
The first ongoing realisations will use telephone lines as a physical channel, and HDLC for the data link layer. This approach is similar to UCA2 and its 3-layer connection oriented stack. COSEM is DLMS based, and it uses ISO/IEC 13239 and its 6 Amendments (asynchronous HDLC with enhanced addressing, error protection and segmentation). Care is taken to be open for interoperability, also with 7 layer OSI stacks.