What is COSEM?
COSEM stands for COmpanion Specification for Energy Metering. It is an interface model of communicating energy metering equipment, providing a view of the functionality available through the communication interfaces. The modelling uses an object-oriented approach.
COSEM models physical metering equipment as a set of logical devices. Each and every logical device has a world-wide unique identifier called the logical device name. Information contained in each logical device is modelled by interface objects. Access to the interface objects within a logical device is modelled by association objects. An association object provides information about the resources available in the logical device in a given context, depending on the access rights.
The interface objects are specific to the metering domain, using well known concepts like register, demand register, profile, clock, schedule etc. There are also special objects controlling access (the association objects) and configurings the communication channels.
The information that is held by an interface object is organised in attributes. Attributesrepresent the characteristics of an object by means of attribute values. An object may also offer a number of methods to either examine or modify the values of the attributes. Object that share common characteristics (same attributes and methods) make up an interface class identified by the class_id and version. On the other hand, interface objects are instances of interface classes.
The first attribute of any object is the logical name, which is one part of the identification of the object. The logical name, together with the class_id and the version unambiguously identifies the meaning of the information presented by any interface object, in a manufacturer independent way.
The COSEM model allows identifying, retrieving and interpreting the information held in any meter in a manufacturer independent, controlled and secure way.
The attributes and methods of COSEM interface objects can be accessed using xDLMS application layer protocol services, turning the information into series of bytes and transporting these over the protocol layers between peer applications.
The DLMS UA has also specified a protocol stack, based on the Open Systems Inter-connection (OSI) model, for transporting the model over serial interfaces, like optical ports, electrical current loop interfaces, PSTN and GSM modems.