New Monitoring Technology at the Förmitztal Dam

To operate the Förmitztal dam, the Hof water authority measures a variety of water levels, including groundwater, seepage, inflows and outflows. The hydrostatic pressure that loads the dam is also monitored at various points to guarantee the safety of the structure. With help from WAGO, the water authority automated some of the monitoring levels as part of the modernization measures taken in 2013.
The Förmitztal dam, commissioned in 1978 and located in northeastern Bavaria, is one of 24 state-owned water reservoirs built starting in the 1950s to ensure sustainable water management. It consists of an auxiliary dam and a main dam, which have a total capacity of approximately 10.5 million cubic meters. The core structure is the earth-filled embankment dam – around 800 meters long, 30 meters high, and 8 meters wide at the dam crest – which includes a partly accessible inspection tunnel.

The Förmitztal dam primarily functions to prevent low water levels on the Saale river, whose source lies only a few kilometers southwest of the dam near Zell at the foot of the Waldstein mountains. The river flows north towards the city of Hof, located around 18 kilometers from the dam. The Förmitz reservoir is supplied by a bypass from the Saale, the Förmitz watershed, and a tributary of the neighboring Lamitz river. The key control level for the Förmitztal dam is located in Hof. During periods of low precipitation, normally between July and September, discharge of at least one cubic meter per second must be ensured to control water pollution and ensure that the water level is high enough at the discharge point for the Hof wastewater treatment plant. Therefore, the water authority discharges approximately four million cubic meters of water annually.

In addition to preventing low water levels on the Saale, the dam also contributes to flood prevention. Since 1991, the water discharge has also been used for energy production following the installation of a turbine. On average, the dam generates around 400,000 kWh annually, which is equivalent to the annual consumption of 125 households. In addition, the water reservoir is also used for recreation – swimmers, boaters and divers enjoy the facility. Significant modifications were made to the measuring equipment in the main dam in 2014. “Up to this point, we measured the levels manually once a week. However, the measuring points were sometimes not accessible in winter, because they were either snowed in or frozen,” explains Matthias Sudholt, who monitors the technology at the dam with his colleagues. A fiber optic cable ring was installed alongside the dam in 2014. Since then, the WAGO-I/O-SYSTEM 750 has recorded the levels and transmitted them to the control center in the operating building of the dam. Here the data is administered and visualized on a panel. An additional expansion of the network is planned for the future.

A total of 40 measuring points for controlling groundwater levels are located on the water and/or air side of the dam. Measurement values, which were previously recorded manually, are now routed through the fiber optic network to various nodes. Data collected at the nodes are supplied to the WAGO-I/O-SYSTEM 750 via an ETHERNET switch and transmitted to the control center, where they are recorded and visualized. The dam also includes 30 measuring points for monitoring the water pressure. This data is still collected on site at this time. The long-term goal of the water authority, however, is the automated transmission of all measured data through the network to the control center. At the center, as well as at various stations, it can be visualized and controlled at a panel on site.

The data from even more remote measuring points is currently transmitted by radio to the control center and supplied to the I/O System 750. It includes the water levels of the Saale in Weißdorf and Hof, the flows from the Förmitz and Lamitz tributaries into the reservoir, the water level in the reservoir itself and the residual water volume in the Lamitz river. The data keeps the Hof water authority informed at all times about the operating condition of the dam and the status of the Saxon Saale. Mobile measurement boxes are occasionally used to record data at measuring points in and around the dam that do not require continuous monitoring. The data recorded by the box is stored locally on the controller and transmitted via Bluetooth^® to the nearest control cabinet. In addition to the Bluetooth^® antenna, a WLAN gateway is installed at the box. This gateway connects to the WebVisu for access to the measured data on site.

To control the smooth data flow, the water authority relies almost exclusively on WAGO control technology using the PFC200. The outside distributor and the Förbau level are exceptions: not WAGO’s standard I/O System, but rather the XTR variant, is used here. The XTR was selected because hazardous increases in potential occur during storms due to the large water surface in the reservoir. This can have a negative effect on the instrumentation and the downstream automation system. “In addition to the 750 Series, WAGO also offers the new WAGO-I/O-SYSTEM 750 XTR as a tailored solution, even for such extreme applications!” says Sudholt with satisfaction. The 787-840 Power Supply, which is protected by an EPSITRON® UPS Management Module (787-870) against unplanned power drops, supplies the power to the I/O SYSTEM for all eight stations.

“The modular design of the WAGO system is the biggest benefit. The system that is currently in use can be expanded without limit by installing the appropriate terminals and boards. The additional components only have to be parameterized and connected; no complicated programming is required”, says Sudholt, describing future expansion options for the automatic monitoring of the Förmitztal dam. “In addition, WAGO offers very fast, reliable customer service thanks to its dense distribution network.”

Text: Kay Miller | WAGO