• Quality Power Electrical Equipments Private Limited

Earthing Transformers

Quality Power Electrical Equipments Pvt. Ltd. offers Earthing Transformers. Earthing transformers are used to create a neutral point in a three-phase system, which provides possibility for neutral earthing. The earthing can be through an arc-suppression reactor, a neutral earthing reactor or resistor or directly.

The design can be a transformer with just one winding, which is zigzag connected. The zero sequence impedance of such a winding is normally quite low, but it can be increased if the purpose is to limit the current through the transformer in case of an earth fault somewhere in the system. Figure shows the connection diagram.

During undisturbed system operation with balanced (symmetrical) voltages the current through the earthing transformer is small & of the same size as the magnetizing current. Unbalanced voltages will cause some higher currents flowing through the earthing transformer, which it must be capable to carry.

An alternative connection to the zigzag is star/delta connection where the delta connected winding will compensate the zero sequence magnetic fields so it will be confined to a leakage field between the star and the delta winding and make the zero sequence impedance of the transformer relatively small. However, if it is desired to increase the zero sequence impedance, this can be achieved by opening the delta connection and insert a reactor or resistor