At the Offenbach an der Queich II wind farm, six onshore wind turbines with a hub height of 139 meters and a rotor diameter of 120 meters generate 15.8 megawatts. They supply more than 40 million kilowatt hours of power a year. It became evident as early as the wind farm planning phase that measures would be needed to manage the harmonics to ensure reliable operation. This is because the modern wind energy systems deployed at Offenbach use IGBT-based inverter technology, which generates disruptive harmonic currents in a frequency range of up to 9 kHz. This leads to stipulated limit values being exceeded at the connection point to the grid operator by several hundred percent at certain frequencies. To avoid the resulting impairment of grid quality and in order to avoid the potential loss of the operating permit, it was necessary to limit the harmonics. "We were aware from the start that limit values would be infringed," says Thomas Schlegel from Power Quality. "Legislation, however, allows a time period for remedying such infringements. Therefore, our high-frequency filter system was retrofitted at a later date."

As a solution, Power Quality developed the first filter concept that lowers the harmonic level in the frequency range up to 9 kHz over a broad spectrum and significantly reduces individual harmonic frequencies. This was a comprehensive solution, from measurement and simulation up to installation and turnkey handover. During the course of the work, Power Quality broke new ground, not only with respect to the inductances and capacitances of the HF filter circuits themselves but also for other primary components such as circuit breakers, fuses, and special current and voltage transformers. All components of the filter circuit system were qualified for use at frequencies up to 9 kHz in coordination with the suppliers.

The filter circuit system is the first of its kind and was put into operation at the start of 2017. Since then, three filter circuits, installed in a concrete station, with tuning frequencies of 189/3,800/5,600 Hz and a total power of 2,800 kvar, ensure the performance promised at the outset. Michael Link, team leader of grid construction, planning & realization at juwi Energieprojekte GmbH, is completely satisfied. He says, "For us, it was very important to receive everything from a single source. Power Quality completed this very complex turnkey project with expertise as well as transparency for everyone involved." Thanks to this solution, unlimited operation of the wind farm is assured. "We have therefore already commissioned MR to also work on our next project."

MR solutions for onshore wind farms

Power Quality: Clean grids for reliable system operation

Johann Hofmann developed the ValueFacturing assistance system for MR. While still bearing the product name MR-CM, it was first subjected to comprehensive testing and examination at Reinhausen itself and found to be of good quality. The system has been in continuous use since then, but now under the name "ValueFacturing" since the update to version 3.0. Hofmann now heads the MR business area named after his software, which has successfully marketed the manufacturing assistance system to other companies in the machining industry. During his factory visit to Stangl & Co. in Roding, the managing partner Hans Stangl and the project manager Florian Dürr reported on the progress they have achieved since the assistance system was introduced to NC manufacturing.

The conclusions of both were overwhelmingly positive. Thanks to ValueFacturing, their company has made enormous strides toward implementing a digital factory. Non-productive downtimes have been eliminated to a large extent, set-up times have been reduced dramatically, and there is now far less need for replacement tools. All this has led to an increase in productivity and efficiency of around 70 percent. As Hans Stangl explains: "In 2009 we reached a point where our manual manufacturing control system could no longer keep pace with our continuing growth and the numerous parts that had to be machined as a result. For this reason, we decided to invest in the assistance system from Maschinenfabrik Reinhausen." Florian Dürr, who implemented ValueFacturing at Stangl & Co. and is responsible for maintaining the system, adds: "A great advantage is that MR works with this manufacturing management solution itself. The benefits are tangible in the highly practical nature of the system and in the continual development and adjustment of the system to meet user requirements."

The integration of the assistance system at Stangl & Co. has led to a complete re-organization of production. In the five years since NC manufacturing was made completely subject to management by the software solution, over 170,000 setup orders have been processed, of which 70,000 were SFP and around 45,000 were NC programs. "In order to handle this huge volume of orders, under our old system we undoubtedly would have needed 20 additional qualified employees – and those are hard to find these days," adds Hans Stangl. Since the start of the project in 2009, the company's sales revenue has almost tripled. During this time, the number of employees also grew by 110 to 253, and the number of CNC machines was increased from 25 to 60. "However, having well-trained and motivated people involved in your company continues to be important," concludes Hans Stangl. "Without them, having the best software counts for nothing."

ValueFacturing is so far the only completely web-based software solution for manufacturing management which connects all systems and roles in a manufacturing process into a network and enables bi-directional, online communication in real time. At the same time, the system can enhance collected information in an intelligent way. Unlike with conventional data-management systems for manufacturing, this creates a consistent, electronic workflow which makes manual data input and forwarding unnecessary.

The two are in luck this time. At the Henderson primary substation close to the city of Auckland in New Zealand, the duo are given four days to service the multiple diverter switch inserts of a 100 MVA transformer and to replace its MA7 motor-drive unit manufactured in 1973 with a state-of-the-art TAPMOTION® ED motor-drive unit. Regular and careful maintenance could keep the tap changers installed here in operation for many years to come.

It's a balmy 25 °C autumn day without a cloud in the sky. Alan and Grant are working in an airy workshop at the primary substation. "A luxury," says Grant while he patiently removes the diverter switch insert from an OILTAP®. "I prefer it when it's cool." Grant neatly arranges the switch components and the diverter switch housing on his workbench, then carefully replaces the copper contacts and replaces the braided leads with new ones. Everything is done carefully and cautiously, which is just as well since Alan simultaneously oversees the winching out of another diverter switch insert that needs complete refurbishment. Altogether, the transformer has three on-load tap-changers and they all need servicing. Alan watches as the device is lifted out of the top of the oil compartment by a cable winch. He then carefully inspects the diverter switch insert once it has been lowered to the concrete floor.

"We have quite a bit of responsibility here," says Alan Brown. "When the restored transformer is put back into commission, we know that we have done our job well and correctly." Alan has been working as a service technician for MR for 18 years. "In a lot of companies, you are just a number but at MR you feel like you're part of the family," he says while summing up his experience.

His son Grant has just recently returned to Australia from a four-week training session in Regensburg for his Premium Service Provider certification. Grant has been with the company for five years since joining MR straight out of school. "I prefer working as a service technician over sitting in front of a computer," he explains. "Sometimes I just see Alan as a work colleague, not a dad. Someone you would like to get a beer with when the job is done."

The enormous Hatebur and Hasenclever hot-forging presses used at Hay Speed Umformtechnik GmbH in Lüchow exert a force in excess of 20,000 N on the red-hot bar stock in order to split it and shape one truck or car component after another in a matter of seconds. Eight ring-rolling mils roll many forged parts to even larger diameters. Each of these systems is switched on and off again several times a day, requiring huge amounts of reactive power when powering up and during operation. When Hay Speed last expanded its fleet of machines, it encountered a problem.

The shift to renewables in the district of Dannenberg, most of which is rural, is gathering pace: Hundreds of photovoltaic systems are feeding environmentally-friendly electricity into the grid of the region's largest electricity provider. When everything is running smoothly, the provider can ensure the grid quality needed for the many connected localities. But expanded production capacity at Hay Speed jeopardized this. Of late, each time the company's systems were started up they caused peaks in voltage in the superordinate grid which couldn't be compensated for. Several times, this had forced the electricity provider to switch off all photovoltaic systems. The owners of these systems and the electricity provider itself rightly demanded that Hay Speed resolve the problem and do it quickly.

A project team from MR designed two reactive power compensation systems for Hay Speed to quickly and reliably compensate for the voltage peaks produced by the switching operations of the large inductive loads. The individually constructed MR hybrid solutions each comprise a pure medium-voltage section for the base load and a low-voltage system of thyristor-controlled stages to compensate for dynamic voltage fluctuations; in each case a step-up transformer raises the voltage from 690 V to 20,000 V.

The systems are installed outside the HAY Speed factory in protective concrete stations. Since they were commissioned, the voltage fluctuation problems have been a thing of the past. Another benefit is paying dividends too. Reactive power doesn't cost the company anything any more because it takes up no more than a third of the free allocation provided by the grid operator.

POWER QUALITY BY MR Wherever rapid changes in load dynamically affect the voltage at the connection point or wherever very sensitive voltage regulation is needed, dynamic compensation systems from MR provide an effective remedy.

In the past, airplanes waiting at the boarding bridges at the Munich airport had to provide air-conditioning themselves. They operated their own auxiliary power units to supply this air. These units burn kerosene, expel large amounts of carbon dioxide and are very noisy. Now, the airport operators are changing course. By mid-year, 64 stationary, environmentally compatible systems are going into operation to supply heat and cooling to docked aircraft, eliminating the need to run the auxiliary power units. The new pre-conditioned air systems can filter and condense outside air directly at the parked position near the building, heating or cooling it depending on what is needed. The processed air then travels into the aircraft cabin through an insulated hose.

A significant component of the PCA systems are the air handling units (AHU), each of which has three drives.  Six-pulse frequency converters regulate their speed. These converters cause current harmonics, which, left unfiltered, would jeopardize the safety of other electronic components. GRIDCON® ACF active filters from MR solve the problem. Modularly designed filters have been adapted to the respective AHU power rating classes and are mostly kept in outdoor air-conditioned housing units designed specifically for this purpose. The MR active filters maintain the voltage quality throughout the airport power grid and ensure an error-free power supply at all points of consumption.

With this solution, the MR experts in the area of Power Quality beat out well-known competitors in a complex bidding process. Their precisely calculated, cost-effective filter design and their impressive service concept were very well received. Regular operation of the first PCA system began in 2014, only a few days after the contract was granted. After a one-week test run, the German Technical Inspection Association (TÜV) confirmed that compliance with all rigorous limit values had been consistently achieved.

GRIDCON® ACF MR active filters take the strain off the power grid, extend the service life of equipment, and improve the safety of industrial facilities. Where current harmonics develop, complex control methods generate current which counteracts the distorted load current and supplements the grid power to become a pure sinusoidal curve. The interfering current harmonics are eliminated and the voltage quality is improved considerably.

Download flyer for industrial version of the Gridcon® ACF

In 1925, when Dr. Bernhard Jansen patented the mechanism he had invented for continuously controlling electric voltage under load, this was the start of a new era – in energy technology and the history of MR.

Since then, MR has been setting standards in the development and maintenance of measurement and control technology. This is demonstrated by the fact that 80 percent of the 250,000 on-load tap-changers sold over the decades are still in use today.

MR recently obtained some impressive examples of the extreme longevity of its products in a customer survey. Around 10,000 customers the world over were asked to help find the oldest MR tap changers still working today. Responses and evidence in the form of photos, certificates, and name plates flooded in from Africa, Asia, Australia, North and South America, and Europe. Some highlights:

  • OILTAP® DIII, constructed 1950, used in the Uniper oil-fired power plant in Ingolstadt
    Our champion – no MR tap changer still in operation today can rival its age. The Uniper power plant is hugely important as a standby plant for Germany's power supply: It helps to maintain voltage and generate reactive power. In times of extreme cold or if major power plants fail, it acts as an "emergency service in the transmission grid" to close the supply gaps. The two generating units each have an output of 386 MW and the plant's five large transformers are checked on a regular basis.
  • OILTAP® DIII, constructed 1954, used by the Jansen group of power plants in Pfreimd
    The Jansen group of power plants in Upper Palatinate was constructed and started up following plans produced by MR's founder Dr. Bernhard Jansen between 1951 and 1961. It is one of the most important pump storage power plants in Germany, supplying valuable control energy. The MR on-load tap-changer is installed in one of the two grid transformers of the pump storage plant. In September 2015 the tap changer was analyzed by MR using the TAPSCAN® VAM procedure: After 61 years, it is still working as reliably as on day one.

Made for generations: Tap changers from MR