By 2020 wind turbines could produce 15% of Europe's energy, which makes electromagnetic interference a major priority for manufacturers and developers alike – both to meet legal requirements and to protect the sector's reputation.
Wind turbines are now sprouting faster than oil derricks did in Texas 100 years ago. Across Europe, so many are being erected that by 2020 they could produce as much as 15% of the region's energy.
The global picture is similar. The world's installed wind power capacity was projected to have reached close to 200 GW by the end of 2010. The Global Wind Energy Council forecasts that wind power could meet 12% of world energy demand by 2020.
But this precipitous growth also brings challenges. The increasing number, rated power and complexity of wind turbines is exacerbating problems with electromagnetic compatibility, creating unwanted interaction between electrical devices. Electromagnetic (EM) emissions can disturb electrical devices and radio services, with highly damaging consequences. Studies show that EM disturbances can even cause electricity meters to measure incorrectly, with obvious financial consequences.
Electromagnetic compatibility (EMC) ensures that all electrical devices in one electrical environment work properly and safely together. Under these circumstances no electrical device should disturb any other electrical device or be disturbed by any other electrical devices.
For green energy providers, the need to convince the wider public of the efficacy of wind power is paramount. Interference effects could damage wind power's reputation for reliability, jeopardizing the wider acceptance of carbon-neutral technologies. EMC management has therefore emerged as a critical means of improving the reliability and operating life of electronic equipment associated with electricity generation by wind turbines.
There are legal drivers too. EMC approval is required by law. For safety reasons, directives worldwide insist on EMC approval, even for fixed installations. In the European Union, for example, both emission and immunity tests have to be approved.
USA FCC pt.15
Japan VCCI
Canada ICES
Europe Directive 2004/108/EC
To this end, the European EMC Directive requires that equipment 'Shall be so designed and manufactured, having regard to the state of the art, as to ensure that: (a) the electromagnetic disturbance generated does not exceed the level above which radio and telecommunications equipment or other equipment cannot operate as intended; (b) it has a level of immunity to the electromagnetic disturbance to be expected in its intended use which allows it to operate without unacceptable degradation of its intended use.'
This Directive refers to the 'state of the art'. For large wind turbines, this means the standard IEC 61400-1 from the International Electrotechnical Commission (IEC). Chapter 10.11 (electromagnetic compatibility) of this IEC 61400-1 document contains a link to the related standards IEC 61000-6-4 and IEC 61000-6-2. These two EMC standards contain all test levels and refer to the 'how to measure' standards.
Wind power is not alone in having to meet such EMC safety requirements. The aviation industry must also make great efforts to comply with safety regulations on EMC. For instance, EMC is why electronic devices must be switched off during take-off and landing in aircraft, as mobile phones can disturb the electrical circuits of aeroplanes through their emitted field. The same applies to the automotive industry and the armed forces. Even consumer products need an EMC approval, such as a declaration of conformity or other requirements depending on the country of use.
The Benefits
The benefits of achieving EMC extend far beyond satisfying the relevant legal requirements. The reputational advantages of EMC are equally important; maintaining the perception of wind power as a clean and effective energy is critical to its continued political and public support, and to the steady flow of investment into the renewable energy sector.
Reliability is another key benefit of EMC, notably in stemming the potential losses associated with wind turbines' downtime – this is particularly crucial for offshore turbines, which are not only difficult to access and maintain but will also account for the vast majority of new generating capacity, according to most current market assessments.
Figure 1 shows the distribution of possible errors on different wind turbine components, from data sets collected since 1989. By combining the electrical subassemblies (electrical system, sensors, control system and generator), the proportion of electrical faults to total faults is revealed to be around 50%.
