Case Labkotec-Functional safety in ice formation monitoring systems

The formation of ice on wind turbine blades can be a significant risk factor. When this starts to happen, it needs to be immediately reported to the turbine’s monitoring system. Ice can put a strain on the turbine’s machinery. In addition, when it falls off in pieces, it can be dangerous for staff and outsiders and can be hurled up to hundreds of meters.

The formation of ice on wind turbine blades can be a significant risk factor. When this starts to happen, it needs to be immediately reported to the turbine’s monitoring system. Ice can put a strain on the turbine’s machinery. In addition, when it falls off in pieces, it can be dangerous for staff and outsiders and can be hurled up to hundreds of meters.

The ice formation on wind turbine blades can be prevented by heating the blades when weather conditions form a risk. In principle, the heating could be on all the time, but that wouldn't be financially sensible. So data on local weather conditions and ice formation is needed in order to know when to turn on the heating. This can then be done remotely, locally, or automatically.

Labkotec has provided wind power companies with an ice formation monitoring system for a long time already. Labkotec’s system consists of an outdoor sensor and indoor electronics and monitoring software.

The principle is very simple. The sensor is on top of the housing containing the machinery, the so-called nacelle, where it detects conditions that cause ice formation. It doesn’t have to be on the blades because the conditions there can be assumed to be the same as on the nacelle.

A single sensor may be enough for an entire wind farm because the weather conditions around each of the area’s turbines can be assumed to be about the same.

The ice monitoring system’s newest version was developed in accordance with the ISO 13849 standard. Its architecture is based on a main safety channel, which carries out the measurement data processing, and a diagnostic channel, which monitors the safety channel’s operation and activates an alarm if there is a problem.

The new architecture ensures that a system malfunction is reported. The internal diagnostics notices problems and reports them. In practice this means, for example, that an error signal is immediately activated in the control room if the correctness of the data cannot be verified.

The principles of functional safety were already established in the 1980s, but only in recent years have manufacturers of control and measuring systems begun to develop these in accordance with standards. This was demanded by wind turbine manufacturers that want to make products that are as safe as possible.

Functional safety often requires the duplication of measurement and safety functions, but in this case a single measurement channel provides enough safety. This is achieved by reducing the chance of faults in the electronics through good component choices and high-quality design, as well as by improving the device diagnostic coverage (DC) with both electronics and software. In addition, it is important to precisely follow established procedures regarding working methods, reviews, verification and validation.

Labkotec has worked together with Espotel, now part of Etteplan, for a long time already. Etteplan has already carried out other design projects for Labkotec in addition to the ice detectors for wind turbines.

The ice detector project began a couple of years ago, when the importance of functional safety became a discussion topic. Labkotec’s customers began to ask about it, and some countries passed regulations requiring that all wind turbines have to receive a performance level (PL) classification.

“The performance level classification of our ice detection system is an important part of the classification of the whole wind turbine.”

“Our customers had already asked whether we could provide a product with a higher performance level classification than the current one. At the same time, we heard that the availability of the processor used in the current product would end. So it was an easy decision to start designing a new product that where the functional safety aspect would be considered.”

Performance level classifications range from PL a to PL e, where PL e is the highest level. “The current product is PL b classified, and our clients hope to get a PL c or PL d classified product from us. We’ve told them that a product like that is on its way. The operators will then decide whether they want the device with the better rating or whether they want to continue with the old one. The choice depends on what the classification of the rest of the wind turbines are.”

According to Aaltonen, Labkotec has basic know-how in functional safety, but this is Labkotec’s first project where it was really applied. According to Aaltonen, choosing Etteplan was easy. “The most important reason for choosing Etteplan as our partner was that they have a lot of expertise in designing functional safety. We’d already had one joint project, and that experience was very positive.” Aaltonen feels it’s easy to work with Etteplan’s experts. “Fortunately we were able to work with the same people as before, and we’ve all become used to how we do things.” He feels the best thing has been how the entire project has been carried out.'

“The daily work following to the required design process and the management of the whole project from Etteplan's side has clearly reduced our work load.” Not everything has gone according to plan, however. “Product development projects of course never go as planned. There are always problems waiting at each turn, but everything was solved along the way in one way or another.”Labkotec’s ice detector is an important product for the company. “It’s perhaps even Labkotec’s most important product.” The same kinds of sensors and systems are used at airports and weather stations. The new ice detector version is now in the final testing phase and will be available next year.

“Etteplan is a significant strategic partner for us. You can say that the collaboration has improved with each joint project. We’ve gotten used to each other’s way of doing things.” Aaltonen thinks that Espotel’s acquisition by Etteplan is good for Labkotec. “It has provided more resources. Collaboration gets even more easy when we can continue projects with the same people but with the support of a bigger organization. “This ice detector project with Etteplan has been a very positive experience in every possible way,” Aaltonen concludes.