2. Transformer protection

2.1 Relais Buchholz

This mechanical relay is located in the oil line (figure 11 ) which connects the transformer tank to the oil receiver. It is sensitive to any gas or oil movement. If this movement is slight, it closes a Buchholz alarm contact. In addition, a tripping command is given by another contact which closes in the event of significant movement. This relay is the only device that can detect ignitions between transformer windings that produce a gas release. All transformers and chokes in oil are equipped with this type of relay.