Earthing transformers are used in electric power grids and their purpose is to create an artificial neutral point the to which an arc suppressing coil or a resistor can be connected. Transformers are manufactured as three-phase devises and if there is no earth fault in the system, they feed the substation with auxiliary power. During fault of power grid the transformer is fed with line phase voltage in neutral point. During operation of the transformer the upper winding terminals are connected to power grid, and the neutral point 1N is connected with the 1A terminal of arc suppressing coil or with the resistor. The transformers can be permanently loaded with auxiliary power demand. The upper voltage winding can be loaded with earth-fault compensating current while the secondary winding is loaded with continuous rated power. The windings of earthing transformers are connected to form the Znyn11 vector group, therefore in case of earth fault allows to distribute short-circuit current over all phases, thus reducing the value of earth fault current in the damaged line.
Three-legged cores made of cold-rolled transformer plates covered with inorganic insulating material.
The windings of transformers are made of electrolytic copper or, on special request, of aluminium. The windings are wound from a wire or strip.
Upper voltage winding is equipped with taps for voltage regulation. Voltage regulation can be effected within the range of ±5%. The transformer ratio can be changed by selecting of desired taps after de-energizing of the transformer.
Capacity: 100-2700 kVAr
Voltage levels: 1-24 kV