From the information provided, it would seem that the transformer is question can be considered as an exemption from the regulation, on the basis of the provision in Article 1.2, as it is connected to a rectifier and provides a DC supply. A hydroelectric power plant is certainly an industrial application.
Disclaimer: Please note that the European Commission cannot provide a legally binding interpretation of the EU legislation, as this is the sole competence of the European Court of Justice. Any remarks from the European Commission services are without prejudice to the position the Commission might take should related cases arise in a procedure before the Court of Justice.