Grounding transformer, abbreviated as grounding transformer, can be divided into oil type and dry type according to the filling medium; According to the number of phases, grounding transformers can be divided into three-phase grounding transformers and single-phase grounding transformers. Three-phase grounding transformer: The function of a grounding transformer is to introduce the neutral point for adding arc suppression coils or resistors when the system is connected in a delta or Y-type connection, which is not possible. This type of transformer adopts a Z-type connection (also known as a zigzag connection). The difference from ordinary transformers is that each phase coil is divided into two groups and wound in reverse on the magnetic column of that phase. The advantage of this connection is that the zero sequence magnetic flux can flow along the magnetic column, The zero sequence magnetic flux of ordinary transformers flows along the leakage magnetic circuit, so the zero sequence impedance of Z-type grounding transformers is very small (about 10 Ω), while ordinary transformers are much larger. According to regulations, when using ordinary transformers with arc suppression coils, their capacity shall not exceed 20% of the transformer capacity. The Z-type transformer can be equipped with arc suppression coils of 90% to 100% capacity. In addition to arc suppression coils, the grounding transformer can also carry secondary loads, which can replace the used transformer, thereby saving investment costs. Single-phase grounding transformer: Single-phase grounding transformer is mainly used for neutral grounding resistance cabinets of generators and transformers with neutral points to reduce the cost and volume of resistance cabinets