Phase shifter at Allgäuer Überlandwerke completely modernized
Picturesquely situated - the phase shifter at Allgäuer Überlandwerk GmbH (AÜW) completely mod-ernized using MR products and expertise.
For over 90 years, Allgäuer Überlandwerk GmbH (AÜW) has been reliably supplying electricity to more than 87,000 customers in the Allgäu region. The coverage area of AÜW is bordered in the west by the coverage area of Vorarlberger Kraftwerke (VKW), an Austrian energy provider that also supplies across borders to many areas in Westallgäu. In order to obtain or supply electric energy between the two networks, a phase shifter transformer with an output of 80 MVA was commis-sioned at the end of the 1990s. After over 15 years, comprehensive retrofit measurements have now been implemented using Maschinenfabrik Reinhausen (MR) products and expertise.
The cooperation with Maschinenfabrik Reinhausen, which has existed for decades, again made it possible for the necessary measures to be carried out by MR. Priority was placed on replacing the two on-load tap-changer inserts for longitudinal und diagonal regulation. The previously used MR on-load tap-changers with oil technology were replaced by modern VACUTAP® on-load tap-changer inserts with vacuum switch technology.
"By observing the general maintenance intervals for the tap changers, we were able to carry out operation for over 15 years without noteworthy faults," said Engelbert Sommer, team leader of maintenance at AÜW. "The diagonal regulator in particular was greatly stressed due to the constantly changing phase angles of both networks (AÜW/VKW). It reliably carried out over 800,000 tap-change operations. Thanks to the vacuum technology which has now been introduced, we will be able to achieve a significantly higher num-ber of tap-change operations at extended maintenance intervals – thereby reducing operating costs and increasing transformer availability. This made the decision easy."
The decision to perform a complete restoration was based on the high number of operations of the on-load tap-changer. Furthermore, after 15 years the control electronics had reached the end of their service lives and were not able to meet the new requirements for a stand-alone operation of the transformer. The TAPCON® with ISM® technology which was newly installed in the control room is now taking over all control and regulation tasks. This includes regulation of effective and reactive power, voltage regulation in standalone operation and the synchronization of the two net-works with configurable voltage bandwidth and phase-angle tolerance. Three TAPMOTION® ED motor-drive units, which have also been newly installed, ensure the safe and reliable drive of the tap changer and de-energized tap-changer.
In order to simulate the complex control and regulation tasks in the most realistic conditions, the entire system – consisting of drives and a voltage regulator – was validated at MR in a special testing facility. After completion of the internal validation, the FAT (Factory Acceptance Test) was carried out at MR together with AÜW. During the on-site commissioning, the regulation and the interaction of the entire system was accepted together with the customer and approved on-site by the MR specialists. "The cooperation with MR has existed for decades and a very trusting relationship has developed over the years. Also in this comprehensive modernization, we were very satisfied with the profes-sional consultation and implementation," said Sommer.