BS EN 13757-1:2021 pdf free download – Communication systems for meters Part 1: Data exchange.
The IC “Register” is formed by combining the features necessary to model the behaviour of a generic register (containing measured or static information) as seen from the client (data collection system, hand-held terminal). The contents of the register are identified by the attribute “logical_name”. The logical_name contains an OBIS identifier. The actual (dynamic) content of the register is carried by its “value” attribute.
Defining a specific meter means defining several specific objects. In the example of Figure 6, the meter contains two registers; i.e. two specific instances of the IC “Register” are instantiated. Through the instantiation, one COSEM object becomes a “total, positive, active energy register” whereas the other becomes a “total, positive, reactive energy register”.
NOTE The COSEM interface objects (instances of COSEM ICs) represent the behaviour of the meter as seen always initiated from the outside. Internally initiated changes of the attributes for example updating the value of a register — are not described in this model.
6.5 Management of a COSEM Device
One physical unit can contain or represent multiple metering units or logical devices. Such a physical unit will have one physical communications interface but multiple metering applications. This calls for a management application inside the unit that performs communications management. This is handled by COSEM as well.
The COSEM Logical Device is a set of COSEM objects. Each Physical Device shall contain a Management Logical Device. The mandatory contents of each Logical Device are:
— COSEM Logical Device Name;
— Current Association (LN or SN) object.
if the “SAP Assignment” object is present then the COSEM logical device name object does not have to be present.
The Management Logical Device shall support an Application Association with lowest security level to a Public Client. The Management Logical Device shall support at least one further Application Association with security appropriate to the network structure and risk.
The addressing of the COSEM Logical Devices shall be provided by the addressing scheme of the lower layers of the protocols used.
6.6 Lower layers
The Lower layers shall include the Physical Layer and the Link Layer. U the seven layer (JSI Model is used, the lower layers shall include network and transport layers. If the IP Model is used, the lower layers are managed by the IP system. The need for multiple communications methods causes the need for multiple different lower layers. All of the lower layers consist of a Physical Layer and a Link Layer. The requirements for the Link Layer are very often closely related to a specific Physical Layer.
In order to specify full protocol stacks, which are needed for meter interchangeability, the lower layers shall be specified/selected as well. Some lower layers have been selected/adopted, and new lower layers will be added as amendments in the future when new technologies mature.
An overall diagram with all of the elements needed and their relationships is shown in Table 6.