The sense of time in Open Metering System

Nowadays, the energy management is a critical task for suppliers and network operators. A wide use of smart meters may improve the quality of service provided by suppliers thanks to the distributed measuring and controlling capabilities. Recently, the smart metering covers not only electrical distribution, but also other commodities such as gas, water and heat. The German standard OMS (Open Metering System) aims to connect in the infrastructure all the different meters belonging to the same system. In the paper, the advantages of the smart meters are examined and the architecture of OMS network is briefly described. The time requirements of typical meter applications are not strict. However, the estimation of the quality of local power network in a building would require a more accurate acquisition system, in which the time of the meters is synchronized below the millisecond. A characterization of the drift between the clocks of two M-bus meters is required to identify the main limits of the native OMS synchronization mechanism. The relative drift is 8 ppm, which means after 24 hours their time references could differ of 0.7 s.