Exclusive Wind Energy Update interview with Peter Dalhoff, managing director at GL Renewables Consulting & Engineering
 
How can developers best use SCADA data to get a better understanding of how to optimise the performance of each component of the turbine?
 
Dalhoff: We would recommend to combine SCADA data with power performance measurements. This applies for the bigger wind farms and the bigger turbines. It offers to diagnose whether the power curves of the turbine are as predicted and as agreed in the contract. If not, it is possible to find the root cause and then solutions.
 
We also use SCADA to see if there are any availability problems with the turbine. Taking a simple example: Sometimes the blade pitch angle has not been adjusted properly. It would lead to losses in energy yield as well as an aerodynamic imbalance, creating higher fatigue loads. This has two disadvantages, one is on the energy yield side and another is lowering the design life. If you are able to detect it, you can simply repair the problem by adjusting the blade pitch angle.
 
First you need a SCADA system and then smart people and smart tools to evaluate the huge amount of data. I think today that’s more key than the SCADA system itself.

What are condition monitoring systems (CMS) likely to offer in the future?
 
Dalhoff: Before we go to the future let’s take a look at how CMS work today. I would like to differentiate between the offline systems and the online systems.
 
The offline condition monitoring system is a mobile device that our inspectors use when they do regular inspections, so it’s a very short term measurement. If we combine CMS with oil analysis and video endoscopy, then we can see upcoming failures. This can lead to preventive maintenance, rather than waiting until the gear box, for example, is completely destroyed.
 
The same applies for the online CMS data, with the advantage for the online system that you can see the trends, because you are monitoring continuously. You can see trends and from that you can see if anything in the vibration signals changes. That gives a more solid data base.
 
I think the key for the future is not the system installed in the turbine; it is more the methods and tools, to evaluate all these data. It’s somehow comparable to the SCADA. On the system side there are also improvements which we will see in the future like rotor blade CMS, which might become a standard feature.

What are the pros and cons of oil and vibration analysis? In what circumstances is the technique best applied?
 
Dalhoff: Oil and vibration analysis are complimentary systems and they should be combined. Independent of whether we are speaking of offline condition monitoring or online, if we do our regular inspections, then we usually do an offline vibration measurement, and it is standard to take an oil analysis.
 
The oil analysis indicates the number of particles in the oil, it gives us the characteristics like the viscosity and other properties. If the oil analysis is taken in regular intervals during regular maintenance, you will also see trends, whether there are any changes in the number of particles or other properties.
 
In combination with CMS, it gives a clearer picture of any potential failure. The current challenge with the CMS is on the planetary stage in the gear box. It is difficult to detect failure on the planetary wheels, whether it is the bearings or the toothing. This is quite tricky, and there it makes sense to look with a video endoscopy after the planetary stage.
 
In offshore, oil and vibration analysis will be standard, each wind turbine offshore will have it. This is due to the size of the turbine: the bigger the site of the turbine the lower the percentage cost of the condition monitoring system. And the benefit offshore is much bigger compared to onshore. If you have a failure outside on sea, it might be very difficult to go there to repair. If you have a system which gives you a very early warning, it will allow you to make preventive maintenance, it will allow you to better schedule the repair actions. Monitoring systems will be absolutely standard in offshore wind turbines and this is why our GL colleagues from the certification side have set CMS as a certification requirement for offshore wind turbines.
 
Installation of asset management systems might not only depend on the technical site conditions, it might also depend on the feed-in tariffs. For example, if the feed-in tariff is set so you benefit from a high energy yield, then of course you would do everything to optimise the performance of your wind farm.

Which individual component presents the biggest monitoring and analysis challenge? What’s the best way to go about monitoring this component?
 
Dalhoff: I think it’s the gearbox and also the generator bearings. The gearbox is one of the components that has higher failure rates compared to other components, and at the same time many of the potential failures in gear box toothing or bearings could be early detected with a CMS system.

When will we see credible integrated management systems on the market for the O&M phase? What will they offer and how will they change turbine monitoring and analysis?
 
Dalhoff: What’s on the market today are single solutions: there are SCADA systems provided by the manufacturers, there are CMS systems provided by the manufacturers or by individual CMS providers and there are some SCADA systems which allow integration of different SCADA data from different turbines, like the GH SCADA. What we’ll need in the future is a combination of CMS, SCADA and asset integrity management (AIM).
 
It will analyse CMS and SCADA data, but it will also look for inspection schedules and lead to preventive maintenance. GL experts in oil and gas have AIM systems, which are about putting performance data into the system, and about smart scheduling of maintenance and repair actions, preventive maintenance, and also about scheduling independent inspections. Finally, the perfect AIM system will automatically generate regular financial and technical management reports.
 
Bigger wind farms, especially offshore, are reaching a size which is comparable to conventional power plants. If we look at UK Round 3 offshore wind farms, or the German far distant offshore wind farms, they will have 80 times 5 MW turbines. And that means that management and management systems for these wind farms also need to be as professional as for conventional power plants. That is why I would like to come back to asset integrity management systems. We need an integrated system which absorbs all the SCADA and the CMS data into one system, which allows, with smart people sitting in front of these systems, to make the right diagnostics, and make the right decisions on preventive maintenance, and a smart maintenance scheduling, combined with regular independent inspections.
 
With the new Germanischer Lloyd (GL) and Garrad Hassan (GH) group competence we will be looking at putting together GH SCADA with CMS and integrating it into an asset integrity management system and also providing services to help clients make the most of such systems.
 
Who do you expect to use the integrated system? Do you expect immediate interest?

Dalhoff: Offshore operators will be the first because the need to do it is the biggest. If you look at the history of wind energy, for example in Germany, it all started with one or two turbines in the backyard of a farmer. They didn’t know about asset integrity management and were very surprised when somebody told them that they had to change oil and do maintenance. A little bit of this thinking might still be there.
 
So it began with small size business and small single turbines and not with the thinking of building a power plant. If you speak with utility companies about this, then there is no doubt that they need an integrated system and will have it in the future.