Elektrizitätswerke Schönau Netze GmbH (EWS) - Case Study

The electricity utility Elektrizitätswerke Schönau Netze GmbH (EWS), based in Germany, near Stuttgart, together with Energieversorgung Titisee-Neustadt GmbH (EVTN) and Kraftwerk Köhlgartenwiese GmbH ensure gas and electricity supply to their customers in the region.

The adjacent energy supply areas together cover an area of around 70km in diameter with elevation changes of up to 1000m.

Elektrizitätswerke Schönau eG was founded after concerned citizens engaged with local government following the Chernobyl disaster in 1986. EWS’ main purpose is the supply of electricity and gas to their own customers, but they also engage in nationwide distribution of electricity generated from renewable sources.

 

To establish an integrated and secure data and voice communication network for their critical operating processes, all three utilities agreed to implement the Smart-Radio-Net network from Smart Radio Net GmbH (SRN) together with radio network components and subscriber units from KENWOOD.

Ensuring reliable and stable radio communication services for gas and electricity suppliers, a reliable and stable communication system is critical. Clear communications during supply switching events are vital, and field personnel must be reached reliably during a power outage or while carrying out maintenance.

Data communication has grown in importance in Smart Networks and is used in the control, measurement and adjustment events in these communication networks, and this was a significant factor in the decision taken by EWS to build a digital voice and data communication network.

Managing Director of EWS, Mr Martin Halm elaborates on the main criteria for their decision: “One of my concerns was that all three utilities should be able to communicate with each other using one system infrastructure and the same type of communications device. Another aspect was to build a radio network with as few physical sites as possible“.

Main consideration: Network Planning

The planning of the radio network proved to be one of the most challenging aspects faced by SRN in delivering its solution. The topology of the area, which is situated close to the highest mountain in the region and the proximity to both Switzerland and France presented major challenges: “The key was to actually secure the frequencies needed. It would have been very difficult to be granted frequencies for a TETRA or Digital Mobile Radio (DMR) system”, explains Stefan Lichy, Director of Engineering and Marketing at SRN.

Thanks to the close working relationship and cooperation with the German Bundesnetzagentur, very narrowband frequencies were found, which were coordinated with the Swiss and French licensing authorities. “Voice and data communication is a speciality of the Smart-Radio-Network, which links these systems. The supplier we selected for the voice communications function is KENWOOD with the technology based on their NEXEDGE NXDN system”, explains Lichy.

From planning to installation

Thanks to the main Smart Radio Net advantage, just three strategically placed repeater stations were required to provide coverage of the service area.

The repeater stations are equipped with NEXEDGE NXR-710E repeaters interlinked by KTI-3M IP network interfaces.

One of the main reasons that installation costs could be reduced was a function of the existing EWS infrastructure, for example, use of its HV pylons. Other reasons include the low power consumption of the NEXEDGE NXDN radio devices which provides the station blackout resilient energy buffering that ensures safe and continued operation for up to seven days.

PMR and telephone functions in one device

With the incorporation of a telephone interface, it is possible to patch the telephone system into the radio system and vice versa. This allows field personnel to directly dial telephone users or extensions and to make and receive telephone calls from their NEXEDGE radios.

Lichy explains the partnership with KENWOOD: “We specified KENWOOD radios due to their excellent performance and robust construction. The radios are perfectly matched to our system”. As remote controlling and switching are becoming more important in the operation of an energy distribution system, the radio system was linked directly with the main EWS utility dispatch centre.

Increase effectiveness, integration and usefulness for the user

A special feature noted by Mr Martin Halm of EWS was the automatic frequency and network selection when moving from one network area to the next. As the topology of the area cannot be changed by the radio, we had a requirement for the radios to change frequencies automatically to handle site roaming events. Thanks to the capabilities of NEXEDGE technology, this requirement was met easily.

Vehicles are equipped with NX-700E mobile radios complete with a GPS dongle. As the location of each radio is known, the radios are programmed with data on where network coverage ends and new network coverage starts, allowing frequencies and networks to be switched automatically based on GPS coordinates rather than RSSI or signal strength.

Another advantage highlighted by Mr Halm is that the mobile radio in the vehicle can be used to communicate with the field personnel’s handheld portable. “It is very convenient as you can use this feature to communicate directly out of a transformer station, for example, which is important in the case of supply switching or similar events”.

Advantages of Smart Radio Net at a glance

Optimised for Data - The modulation algorithm and protocols used in the system are optimised for narrowband data transmission systems and allow for a high utilisation of the available frequency spectrum (optimum bits/hertz).

Integrated Voice - Smart Radio Net offers integrated voice communication together with telemetry over a single radio network infrastructure

Station Blackout Resilience - The radio network solution devised by SRN works with very low TX power requirements (<6W, usually < 1W). This results in very low overall power consumption. In conjunction with a cost-effective uninterruptible power supply (UPS) power cuts of up to one week can be bridged and operation maintained during that period.

List of technical equipment:

• 3 x repeater stations
• 12 x mobile radios, plus one portable for each mobile
• 6 x data and telemetry stations for remote control
• 1 x desktop dispatcher
• 1 x main dispatcher station
• 1 x telephone interface