The Mount Coffee Dam in Liberia utilizes intelligent IO-Link technology, connecting dozens of sensors and actuators over a considerable distance. Its ease of operation, coupled with time and cost savings, has allowed power plant operators to experience the significant advantages of IO-Link in diagnostics and maintenance. The integrated wiring solution, developed by Balluff and its project partner Andritz Hydro, is scalable and can be used in future power plant projects.
The Balluff IO-Link master station with an M12 interface is used to connect sensors and actuators.
In December 2016, the moment finally arrived: after more than 20 years of interruption, the first turbine was restarted, and now all four turbines can each provide 22 megawatts of electricity to the grid. The Mount Coffee Dam, stretching 30 kilometers northeast of Monrovia, the capital of Liberia, dates back to 1966, the year its predecessor was completed. However, it was almost completely destroyed during the Liberian War between 1989 and 2003. The extension of the power plant was not truly started until June 2014, when the Liberian Electricity Corporation (LEC) signed a contract with an international conglomerate to rebuild the dam.
Since the end of 2016, the Mount Coffee Dam in Liberia has been generating electricity for the capital of Monrovia again.
Andritz Hydro, an Australian company, along with several other contractors, rebuilt a hydroelectric power plant on the São Paulo River.
Andritz Hydro is a global supplier providing complete electromechanical equipment and services to hydropower plants. The group is one of the largest companies in the hydropower market, with more than 170 years of experience and more than 7,300 employees worldwide.
Andritz Hydroelectric Company was responsible for the complete hydraulic steel structure, including all electronic components, drive technology, and control systems. They refurbished 10 arc gates on the dam and 4 intake gates on the turbines. The arc gates control the water level on the upstream face of the reservoir and are driven by cable winches. The intake gates introduce water into the turbines and block the flow (flow interruption valve) when the water level exceeds the pressure line and an error occurs. The system is hydraulically driven and includes both electric and hydraulic drive units, as well as various auxiliary systems.
At the Mount Coffee Dam in Liberia, Smart IO-Link connects several sensors and actuators over a long distance.
Although the Mount Coffee Dam stretches for 160 meters and has 10 arched gates every 15 meters, it is not the largest dam to date. However, it requires the collection and transmission of numerous analog and digital signals over its long length to the control layer.
Bernd Schneider, Balluff's Energy Industry Manager, emphasized, "In terms of complexity, dam areas require multiple tasks and network connectivity; in fact, a dam is like a widely distributed industrial system." Balluff, specializing in industrial and factory automation, offers a product range from sensors to linear measurement systems to smart RFID solutions. Ten years ago, the company recognized that IO-Link could solve communication problems between the bus and process layers, as well as the mess of wiring.
No separate wiring is required; simply connect a standard cable.
As a highly standardized point-to-point connection, this universal interface is indispensable for Balluff and its customers because the most needed features are simple wiring, diagnostics, and configuration functions, which are almost universal requirements in today's highly automated systems.
Although Andritz Hydropower has a long-standing partnership with Balluff in the field of marine engineering, they have not yet utilized IO-Link. The pressure of tight deadlines and rising costs are also core issues in power plant construction. It is generally believed that system integrators thoroughly test each component during pre-commissioning, then install them quickly at a remote location, ensuring the components function smoothly and without errors throughout the system.
Berthold Wiesinger, an electrical engineer at Andritz Hydro, said: “Indeed, in many industrial sectors, multi-core cables and electrical control cabinets are still used from the bottom up to the control layer, which is a huge investment in materials and time.”
Balluff's presentation on IO-Link led to the deal: engineers from Andritz Hydropower, together with Balluff's Austrian subsidiary, developed a coherent electrical concept that enables easy wiring, standardization, and modularity.
The Balluff IO-Link master station collects signals within the hydraulic station.
Each of the 10 arc gates and 4 intake gates has two Balluff IO-Link master stations installed in its switch cabinet, capable of collecting up to 20 different signals within the area. These signals, from inductive or electromechanical limit switches and sensors, are used to determine the rotation direction of the arc gates and to control, regulate, and close the valve islands, indicator lights, and illuminated switches. The two IO-Link master stations are each installed in the hydraulic station to connect to relevant sensors and actuators.
Without exception, all components on site use the same standard three-core cable and a uniform M12 connector. When analog signals from specific sensors cannot be processed, compact Balluff adapters can be used to convert the analog signals into noise-resistant digital signals. The Balluff IO-Link master station transmits data to the control layer via ProfibusDB. Due to the system's redundancy, the dam is divided into two sections, requiring a maximum cable length of 75m.
Berthold Wiesinger emphasized, “The advantages quickly became apparent: because we use standard cables and plugs instead of individual wiring, wiring time is halved compared to usual. With IO-Link, you can simply plug in modules and pre-test each one in the factory, which significantly reduces costs.” The IO-Link concept eliminates wiring errors while saving space and providing clear information about the equipment. Multinational corporations particularly value IO-Link's ability to be used with any bus system: the overall structure below the bus layer remains unchanged; only the bus nodes need to be adjusted according to specific countries.
The two-way communication standard also offers significant advantages in other ways: IO-Link's diagnostic information can quickly pinpoint and correct errors, reducing unnecessary downtime. Berthold Wiesinger stated, "For some reason, our sensor junction box malfunctioned during startup, but a colleague easily replaced and reinstalled it. The junction box, with the relevant parameter values, then retrieved data from the IO-Link master. After this brief hiccup, the system was running again." This advantage is particularly evident when the system is not nearby and no qualified personnel are available: IO-Link enables remote maintenance down to the process level. The predictive maintenance concept, with its clear diagnostics and well-defined procedures and guidelines for handling problems, also makes it easier to implement.
Berthold Wiesinger further added: "Smart sensors will improve system availability in the future. Sensors that measure oil temperature and moisture, monitor the temperature of high-pressure motors and the condition of bearings, and can autonomously determine maintenance cycles will also be essential for us in the future."
The number of products that widely adopt IO-Link will increase. For users, this will further optimize wiring, diagnostics, and configuration. "For example, Balluff's analog junction boxes can also connect thermally coupled and similar devices to the module. Using the new safety concept of 'safety superimposed on IO-Link,' Profisafe can now also be used to directly connect safety auxiliary devices. Its advantage is that in the future, this standard wiring concept will only require a single basic device for automation and safety technologies." Mario Ober, who is in charge of related business at Balluff Austria, also emphasized that "this concept achieves the highest PLe/SIL3 safety level."
Since the end of 2016, the Mount Coffee Dam in Liberia has once again been generating electricity for Monrovia, the capital of the country. Berthold Wiesinger believes that IO-Link will be increasingly used in new construction and renovation projects, especially when equipment is aging and there is a need for modern control and electrical concepts.
