Cables and connectors in wind turbines must withstand harsh environments and EMI.
Wind power is the leading form of renewable energy in the United States. In 2016, wind supplied 5.5% of the U.S. electricity supply, according to the American Wind Energy Association, which expects that number to climb to 10% by 2020.
At the heart of wind energy, wind activates sophisticated turbines to facilitate power transmission across a large energy distribution network. This process starts inside a turbine’s nacelle, a covered housing that contains the power-generating components of the machine. Power is generated by one or more turbines and extends from the field to the substation for the grid. This transmission journey creates significant reliability expectations for the cables and connectors.
Several conditions get measured at wind turbine sites, including: wind speed, wind direction, the tension of the rotating blades, temperature and vibration conditions inside the installation, and the power output of the turbine. To disseminate a turbine’s diagnostics to a control center, wind turbines also require an effective communications network.
Reliable components are critical to the successful transmission of this information. These communications networks ensure optimal energy flow from the turbine to the rest of the grid. By evaluating data from the turbine, it’s possible to continually make corrections and optimize system performance. So, it’s important to consider several reliability issues before selecting cables and connectors for the monitoring and control networking systems of wind turbine applications.
Industrial Ethernet vs. Fiber Optics
The choice between an Industrial Ethernet or fiber optic system for wind turbine monitoring and control applications involves weighing different advantages. Industrial Ethernet is well-established, and designers can choose from many suppliers and options to help keep applied costs in line. It also has a reputation for reliability and ruggedness. However, Industrial Ethernet does present some concerns. For instance, copper deployed over long distances can incur some signal loss. Industrial Ethernet is also susceptible to EMI, so cables and connectors must both be fully shielded. Also, the plastic clip on the RJ45 jack is not known for its durability.
Fiber optics are especially suitable for distances beyond 100 meters, and are thus well suited to the remote monitoring essential to wind turbine installations. However, fiber optic cable assemblies are less rugged and, due to their smaller size, are more susceptible to being accidentally cut during installation.
Wind turbines are typically located in remote areas where wind speeds are higher, such as offshore and desert sites. These environments present harsh conditions that can affect the lifetime of a turbine’s components or cause costly downtime for maintenance.
Turbines take a beating from the wind and also have moving parts that cause vibrations. So, components employed in these systems must be vibration-proof. They must also withstand several types of ingress, including dust in the desert, which often finds its way into the nacelle; water from precipitation or sea spray, which can introduce corrosion; and other liquids and oils. Extreme temperatures, such as the ambient temperatures in hot or cold climates, as well as heat that typically builds up inside a turbine’s gearbox or near a generator, are another reliability concern. It’s important to check the manufacturer’s temperature ratings on each component in these systems. Consult the International Electro Technical Commission’s (IEC) IP ratings to see which companies offer components that provide ingress protection from solids and liquids, as required by your application.
Signal Integrity of Ethernet
Electromagnetic interference (EMI) is always a concern in wind turbines. Moving parts inside of wind turbines not only cause vibrations, but are also a good source of EMI. The high-voltage electricity generated by these turbines is another major EMI source. Both conditions can easily affect the sensors and control systems, as well as other sensitive electronics. For example, EMI could affect the signal from the wind vane to the programmable logic controller (PLC), causing the nacelle to point in the wrong direction, decreasing the power generation and efficiency of the turbine.
Everything in the system must be shielded, including wires running to the device and the control cabinet, mating connectors, and interconnections of the connector shields.
Signal integrity is one area where cable and connector vendors can be very helpful to designers. Will Stewart, industry segment manager for energy and wind energy for HARTING, says that some vendors can provide entire systems that are pre-tested and pre-assembled with EMC (electromagnetic compatible) connectors, cables, and cable glands. “You want to reduce the transfer impedance in all parts of the connection,” he said.
Vendors Offer the Best of Both Worlds
The wind turbine industry has expanded quickly and is continuously improving its efficiency. In just a few years, industry-standard sub-megawatt outputs have become multi-megawatt outputs. Partnering with cable and connector vendors can help provide solutions to the reliability issues presented here and help system designers navigate the trade-offs between Industrial Ethernet and fiber optics. Some companies, like HARTING, with its versatile push-pull connectors, can accommodate both options. “Or, you can do signals from an anemometer all through one connector,” said Stewart. “It is connected or disconnected with one hand.”
As always, components ultimately ensure the success of the system. When selecting cables and connectors for a wind turbine’s monitoring and control systems, make sure they can meet your data handling needs, withstand extreme operating environments, and maintain signal integrity. Be sure to check with cable and connector vendors to see if they can provide custom or even all-in-one solutions for your particular reliability requirements as well. Your engineering staff or outside consultants can make sure your choices adhere to best practices for your particular situation. Reliable cables and connectors can help maximize wind turbine uptime. Choose well and they could even outlive the installation.
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