By Dave Karpenske, CEO
There has been much discussion over the last few years regarding life-extension strategies for wind turbines approaching the end of their 20-year design life. Many ideas involve auditing and restoring gearboxes, or replacing and upgrading turbine components.
These are important concepts, but what’s typically missing from these discussions is attention to the modernization of the systems’ control and communication networks between turbines and their related infrastructure. Most likely this is because of time and costs constraints. It is a daunting task to rip, replace, and re-install new cabling (structured or fiber) typically needed to achieve the necessary bandwidth performance. Never mind dealing with the impact these upgrades would have on the communication slip rings.
Slip rings are commonly used in turbines to transmit electrical signals from a stationary nacelle to the rotating hub. Chances are they will also need upgrading at some point to effectively support broadband IP protocols.
The cost of retrofitting a standing turbine with new wiring can prohibit upgrade strategies until the network goes down. Moreover, many older systems were simply not designed to mitigate the electromagnetic or radio-frequency noise in a turbine that can have a performance impact on Ethernet signaling.
These factors lend to barriers that have up until now, made upgrading a turbine’s network to support new sensors, along with control and automation systems, a difficult proposition for many turbine owners and operators. However, there is reason for the wind industry to find ways to take advantage of proactive maintenance as condition monitoring and data collection systems become increasingly more common.
At the control and communication network level, there have been attempts to implement new communication technologies into wind turbines over the last few years to facilitate the repurposing of UTP or unshielded twisted-pair wiring into broadband channels (such as VDSL, or very-high-bit-rate digital subscriber lines). Unfortunately, these communication technologies have not done well in the noise environment present in turbine applications, especially when attempting to communicate across rotating serial slip rings.
Another approach considered for use in turbine networks is wireless communication. But once again, the noise issues within the nacelle and non-deterministic latencies or delays inherent with wireless technologies, has made it a poor choice for turbine use to date.
A new method now available promises to cost-effectively address network issues at wind farms and provide an upgrade path to improve turbine performance and cost of operation. This technology is already getting deployed throughout the industrial process and control automation markets, and has recently been introduced to wind-turbine applications.
The new “InterMax” technology supports communication and control system upgrades to Ethernet protocols by using original serial wiring and slip rings in the turbine design. InterMax products from PCN Technology provides turbine operators the capability of repurposing existing wiring to facilitate deployment of ethernet networks by reusing all of the existing cabling currently in operation.
Here are four application use cases for use in wind turbines.
1. Full repurposing of legacy serial wiring to transport Ethernet protocols (including Ethernet, Profinet, Modbus TCP IP, and others) At some point in its lifetime, there is a need to upgrade a wind turbine’s control and communications networks from older serial (RS-485) technology to operate IP or Internet protocols such as Ethernet, Profinet, and Ethernet I/P. Typically, this would require the time-consuming job of ripping out and replacing the legacy or older wiring with new structured cabling. Now it is possible to repurpose the legacy two-wire twisted pair wiring to carry a new desired IP protocol when using InterMax products.
This option works well for field upgrades, and supports multi-drop topologies and 100BASE-T (a common Ethernet standard that supports data transfer rates up to 100 megabits per second). It also saves time, costs, and the complexity of planning and implementing a full wiring upgrade. The repurposed wire can also inherently work in extreme noise environments and operate broadband signaling over unshielded two-wire networks, making it ideal for use in wind turbines.
2. Maintain legacy serial communications while adding Ethernet (new features) onto the same wiring. Several upgrade scenarios make it necessary to continue operating the legacy serial communications and control applications in a turbine, while adding select IP sensors and functions. Ultimately, both protocols (serial and Ethernet) must operate simultaneously during the process.
Until now, it has not been possible to operate both protocols on the same wiring at the same time. This issue is compounded by a need to communicate the serial and Ethernet protocols over a legacy serial-communications slip ring. However, with a new “dual protocol” communication capability, it is now possible to repurpose the two-wire network to communicate IP (Ethernet) and simultaneously and asynchronously communicate the legacy serial traffic over the same two-wire network — while communicating through serial slip-ring channels.
This means an older wind turbine can add IP functions and not disrupt its serial technology operating at the same time. Therefore, it is possible to add new networking capabilities that improve performance and reliability in a turbine while maintaining its old system. This extends the life of older turbine systems. Such an upgrade supports up to 128k baud serial (the speed of communication), and simultaneously and asynchronously supports 100BASE-T packet protocols.
3. Install wiring in series with any slip ring (except optical), and measure brush wear and material deposition on the pads. With advanced InterMax signaling technology, it is possible to measure and store signal-to-noise (s/n) ratios. The measurement of noise values is fundamental to how PCN Technology establishes encoding FFTs (Fast Fourier Transforms) and decoding IFFTs (Inverse FFTs) to maximize the bit rates per carrier (OFDM scheme), or orthogonal frequency-division multiplexing, being a method of encoding digital data on multiple carrier frequencies. FFTs are DSP algorithms that convert signal data from the time domain to a more useful frequency domain. The IFFT does the opposite.
Unlike conventional DSL (Digital Subscriber Line) used for high data bandwidths, this approach re-measures the signal-to-noise ratio and re-establishes encoding and decoding values every few milliseconds. This is why it is possible to receive such high bandwidth speeds through old, noisy two-wire networks and operate smoothly through the spurious noise of slip rings.
Where DSL makes an initial measurement for encoding and decoding at power-up, InterMax technology makes continuous measurements every few milliseconds, and modifies the FFT and IFFTs to adjust each carrier for intermittent and sporadic noise changes.
Perhaps most importantly, these signal-to-noise values are captured and stored. This provides an opportunity for analysis and review of how well a slip ring is performing over its serial or IP communications path. Analysis of these signal-to-noise values also means it is possible to determine the condition of the brushes and material deposition on the pads.
By developing signal-to-noise system profiles (templates), an operator can determine when communications will begin to fail and use data as a predictive tool for servicing slip rings.
4. Implementing new cabling to a system with IP infrastructure. There is value in using InterMax technology for turbine control and communications even when an IP slip ring and structured cabling is already in use. This scenario applies to new factory builds and field upgrades because the problems of brush wear and material deposition still occur in IP slip rings.
Benefit of upgrading an existing Ethernet path through a slip ring include in-situ slip ring condition measurement and frequency modulation signaling with constant adjustments. This means communication can continue to operate even when a slip ring’s brush or pad connection has degraded to the point of becoming capacitive coupled. It is then possible to communicate across a degraded slip ring well after normal Ethernet devices stop working or reach failure mode.
This ability extends the usable time between service calls, saving a technician’s travel and repair time, and other related costs. Additionally, a new IP technology turbine with InterMax wiring could use a lower cost serial slip ring for communications. By retrofitting wiring in wind turbines, it is possible to enhance communication and improve turbine performance.
Filed Under: News, O&M