Operation of the Niederhausen hydroelectric power plant also includes monitoring the level of the adjoining reservoir. The values recorded as well as the operating states of the flood and ground water drainage pumps are transmitted via the Trusted Wireless system to a master wireless module installed in one of the towers.
From there, the data is forwarded to a central controller in the power station building via SHDSL modems.
The Niederhausen municipality in Rhineland-Palatinate is not only famous for its idyllic location in Weinbergen. The area also has a reservoir with a volume of 800,000 cubic meters - a popular attraction for many amateur athletes and people looking for rest and relaxation.
As well as being a place of recreation for locals, the reservoir is also an important part of the power supply to the Nahe-Hunsrück region. This is because a hydroelectric power plant and a transformer station belonging to the RWE Group in Essen are located on its banks. The plants are operated by RWE Deutschland AG and RWE Power AG.
The difference in height determines how much power is generated
In 1926/1927 the former Rheinisch-Westfälische-Elektrizitätswerk Aktiengesellschaft built a 110/20 kV transformer station and laid a 110 kV dual line from Koblenz to Niederhausen. The municipality became an important region, as a hydroelectric power plant that could be combined with the substation was constructed at the same time. As a result, in 1928 the energy producer was able to feed the power accumulated from Niederhausen's water into the mains system for the first time.
The Niederhausen hydroelectric power plant is still one of the largest plants in the Rhein-Nahe-Hunsrück region. It currently supplies around 1400 customers with power. The reservoir plays an important role in the generation of energy. Its water is fed through a 760 meter long headrace channel to two vertical Kaplan turbines, which are installed in the power station building. The rotary movement of the wave drives a generator, which is connected to the turbines via vertical shafts. The water is then fed back into the region via the lower-lying tailrace channel.
The amount of power generated depends on the difference in height between the headrace and tailrace channels. This means that less energy is generated when the level in the tailrace channel increases in the event of a flood and the difference in height in relation to the headrace channel decreases. The optimum flow rate in the channel is around 45 cubic meters per second. At this rate, both turbines generate the maximum amount of power.
Monitoring stations forward signals to the master wireless module
The reservoir has a weir system that controls the supply of water into the headrace channel. In order to guarantee the reliable operation of the power station, the level of the reservoir needs to be monitored. As such, the water level needs to be measured and the flood and ground water pumps need to be monitored. A wireless system was installed around the reservoir to enable the operating states of the pumps and the water level to be continuously monitored. A cable solution would have been too complex and too expensive in this case. One of the towers is used as the central point of the Trusted Wireless system from Phoenix Contact. The building houses a control box containing the master wireless module that is connected to a PROFIBUS gateway.
A level control house and three small pumping stations are used as additional monitoring stations. Wireless modules combined with analog or digital input and output devices are installed in the four plants. The wireless components transmit the signals to the master wireless module in the tower. In the level control house, the current water level in the reservoir is continuously recorded, which enables employees to react quickly to any changes. In the past, they had to read the data manually from a flood marker, which was extremely time-consuming. Fault messages from the pumps are recorded in the small pumping stations and forwarded wirelessly to the master module in the tower.
The PROFIBUS SHDSL modem from Phoenix Contact is a cost-effective solution here. A modem is installed in the tower, where it is connected to the PROFIBUS gateway. The second device is located next to the Vipa controller in the control cabinet in the power station building. The Vipa controller, which acts as the PROFIBUS DP master, records all signals generated in the plant. It is connected to a PROFIBUS gateway (PROFIBUS slave) via the SHDSL modem. The PROFIBUS gateway installed in the control box in the tower uses its RS-232 interface to communicate with the master wireless module from the RAD-Line Serial product range.
The master wireless module establishes the connection to the four remote repeater/slave wireless devices, whereby the system can be extended up to a maximum of ten wireless modules. With a clear line of sight, the Trusted Wireless technology can cover typical distances of two kilometers between two devices. Every repeater/slave wireless module can record signals via the alignable I/O extension components and at the same time transmit data to other wireless devices. The repeater function enables longer distances to be covered and obstacles to be bypassed.
SHDSL modems guarantee reliable wired communication
Since the control technology in the Niederhausen hydroelectric power plant is set to be upgraded, the wireless system has already been configured to record additional signals according to Bernhard Beicher from RWE Power AG in Bernkastel-Kues. This includes transmitting motor currents to the pumps. As mentioned above, the signals are recorded in the tower and converted directly into the PROFIBUS protocol via the PROFIBUS gateway. The controller, however, is installed in the power station buildings around 800 meters away. To connect the central controller and the PROFIBUS gateway, those responsible have used an existing cable connection in order to save money. As this is just a copper cable, however, it cannot simply be used as is to transmit the PROFIBUS signal. This is due to the fact that, depending on the transmission speed, the segment length is limited to up to 100 meters.
Transmission speed is set automatically
The RAD-Line Serial-IO wireless solution works in the license-free 2.4 GHz frequency band. The wireless modules are configured with a free of charge piece of software. A wizard guides the user through the necessary steps. The gateway can also be easily integrated into the controller's PROFIBUS DP network as a slave device via its GSD device description file. As such, predefined wireless stations in the field, which have been extended to include alignable analog or digital input and output modules, can be easily incorporated into the wireless system. The PROFIBUS transmission speed of up to 12 Mbps is set automatically, i.e., without the need for configuration. The PROFIBUS address of the gateway is selected via a DIP switch.
“The RAD-Line wireless modules, the PROFIBUS gateway, and the SHDSL modems were extremely easy to configure and start up”, explains Bernhard Beicher, responsible for startup. “Wireless communication will continue to be a practical alternative to wired solutions for us in other areas of the waterworks”, adds Bernd Gumm, Director in Niederhausen.
Reliable wireless system for I/O and serial data
The robust and reliable Trusted Wireless technology from Phoenix Contact is ideal for use in industrial systems for the transmission of small amounts of data cyclically over long distances of up to three kilometers. Digital switching signals and analog sensor signals are recorded and forwarded by the RAD-Line I/O modules. The product line is available as a unidirectional and bidirectional system. In addition to point-to-point and point-to-multipoint connections, repeaters enable obstacles to be bypassed and longer distances to be covered.
The RAD-Line Serial product range enables serial data to be transmitted via an RS-232, RS-422 or RS-485 interface and analog and digital signals to be transmitted in a meshed network. In a wireless network, which consists of a master and up to 254 slaves, every slave module can also work as a repeater. The easy-to-use system components are certified according to the 94/9/EC (ATEX) and IECEx directives, which means that they can be used both nationally and internationally in potentially explosive areas (zone 2).