Fibre-optic: first choice for reliable data in wind turbines

Building reliable control and data acquisition in wind turbines requires careful consideration to guarantee insulation from high-voltage glitches and unwanted signals.

However, in order to create reliable wind farm, that can be built over large areas and with adequate protection against high-voltage glitches and unwanted signals, the supporting network and medium must be built with strict design considerations.

For example, in order to transmit utility-grade AC power over long distances, a transformer is typically installed at the bottom of a given tower. This provides voltage conversion from the low voltage generated by the wind turbine, to medium/high voltage for transmission. A rectifier converts noisy AC power to DC power, and an inverter then converts DC power back into clean and reliable AC power.

The switching of these devices is usually controlled by a DSP embedded controller via a link with high galvanic isolation capability. Building reliable control and data acquisition therefore requires careful consideration to guarantee insulation from high-voltage glitches and unwanted signals.

 

 

Condition monitoring

Most modern wind turbines have intelligent features to monitor and control the system under varying wind conditions. Atmospheric sensors detect wind speed and direction. Other sensors monitor the condition and strength of the turbine’s parts to avoid run-to-failure.

Since wind turbines can be exposed to extreme weather conditions, such as storms and lightning, this monitoring system needs to provide both high-voltage and high-current isolation. In these types of conditions, Fibreoptics have become the preferred choice of medium in various applications.

Fibre-optics can offer much higher voltage and current isolation properties than copper cables and other isolation components. Besides good isolation properties, the right fibre-optic product can also provide excellent signal integrity due to inherent immunity from Electro-Magnetic Interference (EMI). Fibreoptics, using Ethernet protocol in this case, therefore offer the potential to enable monitoring over long distances with reliable data transmission.

 

 

In the nacelle of the wind turbine (Figure 2), short link distances can be easily and effectively designed using a combination of fibre-optics and Avago’s HFBR-0500Z plastic fibre-optic cables. Connectors with snap-in, latching and screw-in designs are available which allow for field repairs, maintenance and installation. For greater ESD and EMI protection, Avago’s HFBR-x506AMZ series of transmitters and receivers features a metallised packaging that provides excellent shielding. The SMA-styled connector also works well in areas with vibration and mechanical shocks.

 

 

Wind-farm networking

Data collected from individual condition-monitoring systems needs to be fed back to the control centre. Longer link distances require HCS and multi-mode fibre. If wind turbine towers are greater than 100 meters in height, these types of cable are also worth considering for links within individual wind turbines as fibre cables are lightweight and offer resistance to harsh environmental conditions.

Avago Technologies has developed a series of fibre-optic transmitters, receivers and transceivers that perfectly suits wind turbine monitoring systems and networking applications. The range includes parts from 650nm, 820nm or 1300nm, with data rates up to 160MBd to suit different link distances.

Industrial fibre-optic components, also from Avago Technologies, provide high reliability for data acquisition, as well as control and isolation. Featuring outstanding performance in high insulation voltage and high immunity to EMI, these products are able to be installed and operate in close proximity to power-carrying conduits which emit disruptive electrical interference.

As the demand for renewable energy grows globally, wind turbine designs are continuing to grow in size. For the many applications in this power generation market, the breadth of Avago’s industrial fibre product range can provide the optimum data-rate and link length.

 

 

Development boards HFBR-0538 - 2MBd Interbus, HFBR-0539 - 12MBd Profibus and HFBR-0540 - 10MBd Sercos are available to members of the Future Board Club. To apply for the development board, and membership of the Board Club, go to www.my-boardclub.com/manf-offers.htm This offer is free and subject to qualification.

 

Avago Fibre Optic in Wind Turbines Design Note