We were there

The rapid growth of Electric Vehicles, rooftop solar, and heat pumps is reshaping the power distribution grid of Germanys oldest city, Trier. To keep up with these changes, the local utility had to upgrade its metering systems. The requirements were clear, but not easy to meet. The solution ultimately met every requirement.

Trier’s distribution grid is typical of many German cities: a dense urban core with transformer stations integrated into buildings, alongside commercial areas and expanding suburban neighborhoods with growing numbers of PV systems, heat pumps, and EV charging infrastructure.

As in many regions, the electrical infrastructure was not originally designed to handle the increasing loads from these new consumers and distributed generation. Utilities also lack a clear view of where surpluses or bottlenecks occur within the grid, and what actions to take.

New regulations are creating additional pressure. Since early 2024 a new German energy law (Energy Industry Act (EnWG), section 14a) requires utilities to connect new loads such as heat pumps and private EV chargers without delays. In return, utilities may temporarily limit power consumption, for example at charging stations, if the grid is at risk of overload. However, this kind of control requires up-to-date load flow data.

Given these challenges, Stadtwerke Trier, the city‘s municipal utility, began upgrading its transformer stations with modern digital metering systems. The existing devices no longer met regulatory requirements and had to be replaced. The utility defined clear technical criteria, evaluated several vendors, and ultimately selected a solution from Janitza. “The devices had to work for both new installations and retrofit projects. Especially in existing infrastructure, limited space is a major issue,” says Tobias Reinhard, esponsible for system planning and retrofit projects in transformer stations.

Stadtwerke Trier primarily relies on Janitza’s modular UMG 801 power analyzer, which can be expanded with additional modules. “For retrofit projects, the 800-CT8-LP current measurement module is particularly well suited,” explains Janitza Sales Manager Ludwig Resch.

The module requires minimal space, offers eight current measurement channels, and can be installed flexibly within the station, even in confined or complex installation environments.

Andreas Faber, Head of Operations and Electricity at SWT, was pleased with the initial installations: “The ability to retrofit safely while the stations remain in operation is crucial for us, since shutting them down is not an option. With around 450 stations, time is also a critical factor. If we can save two hours per station thanks to easier installation, that’s a significant advantage.”

Digitizing the transformer stations also included integrating measurement data into the utility’s control system. The operators wanted to continue using their own systems—and Janitza’s open interfaces made that possible. “We have full access to our data at all times. There are no system-level restrictions, and we don’t need special software to access the data. With other systems, that often involves licensing fees. Not with Janitza,” Reinhard explains.

In addition, the UMG 801 analyzers provide comprehensive power quality monitoring. Operators can detect anomalies such as harmonics and assess whether they may become critical. “This is becoming increasingly important, especially when it comes to supplying our commercial customers,” Reinhard adds.