Industrial Automation

Underground Substation Design Delivers High Reliability


Transformer substations are used to convert the high voltage levels of electrical distribution systems to lower voltage levels for use by homes and businesses. Locating substations can be difficult however, as many people believe they are unsightly and that they reduce property value.

This challenge is even greater in urban environments where the demand for power is high, but the space available for the construction of a transformer substation is limited. This was the situation that faced the German power company, Mainova AG (Mainova), a large regional energy supplier, servicing about one million people in the Frankfurt area.


The company wanted to meet the rising energy demand of its customers in the densely populated center of the city. After weighing several options, Mainova decided to go forward with a pioneering solution, that is, an underground electrical substation. 


This innovative approach was able to fulfill all the functions of a traditional transformer substation and limit the space required above ground to a small access building. Let’s take a look at how the communications infrastructure of this state-of-the-art facility was designed to reliably deliver the power needed.



The innovative Mainova underground substation is located only a few hundred meters from the Old Opera House, shown above, in Frankfurt, Germany.


The Key Parameters of This Electrical Substation Project

The driver for this project was an increase in demand for power in the Frankfurt metropolis as more and more companies located in the city center. The key customers in this area include many financial services companies, making reliable power delivery very important.


The location of the substation is in a central area that is densely populated and close to the beautifully restored Old Opera House. Safety was therefore another primary concern. Other requirements for the substation were:

  • Three transformers had to convert the electricity from 110,000 volts to 10,000 volts for the local distribution network
  • The transformer substation had to be operated remotely from a separate control center, including monitoring, control and management
  • The location of the substation, between a main road and a river, increased the risk of ground water contamination
  • To create a standardized network topology for Mainova substations that was compliant with IEC 60870-5-104 and that would also apply to future IEC 61850 substations
  • Given the pioneering nature of the project, Mainova wanted to work with partners with proven expertise

A Ruggedized, Robust, Reliable Substation Solution

Staff from Belden’s European Competence Center (a service center offering consulting, training and support) and a system integrator (Kapsch Carrier Solutions) worked with a team from Mainova to plan the network design. A ring topology was chosen for the communications infrastructure of the underground transformer substation.


Within the plant, compact managed Ethernet switches were installed. These switches have a high level of resistance to shock, vibration and electro-magnetic interference and can be used for an extended temperature range of -40°C to +70°C (-40°F to 158°F). They are also IEC 61850 compliant. The field-level switches are connected to backbone ruggedized rack-mount switches for Fast Ethernet.


Additional network products were used to allow for balancing during peak periods. Redundant communication for the complete network is guaranteed by using switches that support the Media Redundancy Protocol (MRP). The benefit of this protocol is the optimization of reconfiguration time in the case of network outage.


For control and monitoring of the transformer substation, the local network was designed to connect all control and safety devices. A SCADA system assembles the reports and measurement values from the individual field control devices and transfers them to the control center via the external backbone network. Commands from the control center are distributed via the local network to the appropriate field control devices.


The final network provides the highest level of reliability, availability and security. Downtime is further minimized with a five-year warranty and complete customer service package. The whole project not only met all the original criteria, it was also completed on schedule and within the budget framework.


An Urban Power Substation with Community Approval

“Underground substations are the future of electricity in urban areas, and this project was a win for everyone. Our customers have the reliable energy they need, the community is happy that we minimized our footprint and maintained green space in the park by building a garden on top of the installment. Plus we have a secure system that will meet the electricity needs of this area for at least another 40 years.”

– Andreas Hallwirth NRM Netzdienste Rhein-Main GmbH, a subsidiary of Mainova


For a complete write-up of this project, including a network diagram and photos, download the Mainova Case Study.