Unbundled Smart Meter Design Solutions and Lessons Learned

By Mihai Sanduleac

In April 2015 the Horizon 2020 project Nobel Grid announced the unbundled smart meter, an architectural systematization in which smart meter functionalities are adequately grouped in two separate (unbundled) parts, making the ensemble both metrology-proof and highly flexible. Lessons learned during the period of design, as well as technologies applied for preparing the project rollout scheduled for 2017 are now presented. Moreover, two new European projects – WiseGRID and SUCCESS will use and extend the functionalities, allowing a more flexible, complex and secure meter, with the aim to increase the security of critical energy infrastructures based on smart metering.

In April 2015 the Horizon 2020 project Nobel Grid, which is developing within a consortium led by ETRA I+D from Spain an unbundled smart meter (USM), was announced.

This is an architectural systematization in which smart meter functionalities are adequately grouped in two separate (unbundled) components. One is for metrological and hard real-time functions, called the smart metrology meter (SMM), which is intelligent but has fixed (freeze) functionality and high security of recorded data (black box-like standard). The other is smart meter eXtension (SMX) that comes with the high flexibility needed for new functionalities, to be deployed during the meter’s lifespan and to support the future evolution of the smart grid and energy services.

After introducing some early pre-deployments of USM prototypes, the project schedule for 2017 is to deploy two variants of the USM concept in the five demonstrators: Alginet, Spain; Terni, Italy; Manchester, United Kingdom; Flanders, Belgium; and Meltemi, Greece.

One variant is a USM solution using meters that currently exist as SMM and a separate physical SMX with the entire functionality and high flexibility using public Internet Protocol networks and concurrent connections of remote actors.

The other is a USM designed from scratch, named SLAM (smart low cost advanced meter) which has advanced functionalities in the SMM part and the same SMX as a meter gateway toward the energy ecosystem. The latter is referenced below as the commercial name of the USM concept.

Many lessons were learned with the USM during the design phase of the new SLAM.

As the repository of both billing data and of privacy-sensitive data, vulnerable over the Internet, SLAM needed careful design to balance flexible interconnections and controlled access to facilitate multiple-channel simultaneous communication. For this, a database-centric architecture with enhanced role-based access control (RBAC) was chosen. This gives specific rights for each separate actor, using a superposition of country-specific and user-defined rules.

Internet exposure required cyber security be treated at the highest level, because SLAM is practically a bank of energy data. Billing data, which supports the smart grid ecosystem, is an essential component. Each participant is entitled to communicate with SMX only through its own virtual private network, with its own credentials and in a segregated environment controlled by a trusted zone of the SMX part of SLAM. With this strategy, external interaction can only occur within a controlled environment; access to the database is made through connections using JSON messages interpreted and controlled by the powerful RBAC system.

For the solution of using existing meters as the SMM, the consortium spent much time in integrating these meters with the SMX. The five demonstrators faced a diversity of meter designs with a multitude of protocols, some non-standard. Some used standards but with custom modifications or deviations in implementation. Others still presented data security issues related to main functionality granted by the distribution system operator.

With this design, SLAM acts as a complex smart meter serving a multitude of areas and bringing real-time support for:

• Smart grid – by delivering RTU-similar real-time data in a traditional or Synchro-SCADA mode,
• Power quality – by allowing essential PQ assessment on continuity of supply and on voltage level;
• Energy services – by supporting energy records load profiles down to one minute resolution combined with appropriate recorded events, in order to properly record services such as demand response;
• Dynamic energy markets – by allowing real-time interaction between the market and the prosumer;
• Local production and storage control – by allowing to host specialized software agents which can control and optimize use of these local resources;
• Security and privacy – through means already mentioned.

It brings even support for yet-unknown functionalities at the time of a smart meter rollout, as new software modules can be developed and deployed during the lifespan. One situation that could be handled without conceptual changes is the representation of smart appliances of the prosumer through the new Smart Appliances REFerence (SAREF) ontology, introduced by ETSI at the end of 2015, as a DLMS/COSEM to SAREF mapping agent which can be deployed remotely during the lifetime of SLAM.

With all this functionality onboard, SLAM is proposing a third generation smart meter, having multiple simultaneous interaction with different participants, based on different protocols, such as IEC61850, DLMS/COSEM, OpenADR and MQTT Publish-subscribe – each in its own OpenVPN secure connection.

It is also one of the first Linux-based smart meters as well as a powerful Internet of Things (IoT) meter, able to connect securely over the ubiquitous internet, to support the European Union Digital Economy and Society policy.

The unbundled architecture has been recently chosen to be used also in H2020 project WiseGRID led by ETRA I+D and the concept is to be extended in another European H2020 project named SUCCESS. The latest will occur within a consortium led by ERICSSON from Germany, where the meter gateway is communicating also with a low-cost Phase Measurement Unit (PMU). In the SUCCESS project the ensemble is called NORM -- the Next generation Open Real-time Meter and will help to ensure the security of critical energy infrastructures based on smart metering.

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