One kind of transformer is specially used to distribute power to some large transformers. Large transformers generally need more power to drive their work, so some distribution transformers are often installed around this kind of transformer. This distribution transformer is different from the distribution device of the transformer, and the transformer distribution device is only used to transmit power, The distribution transformer can transmit both power and voltage.
High and low voltage sides of distribution transformer shall be equipped with fuses. The vertical distance from the bottom of the fuse on the high voltage side to the ground shall not be less than 4.5m, and the horizontal distance of each phase fuse shall not be less than 0.5m. In order to facilitate operation and the fuse tube can fall down smoothly after fuse fusing, the axis of the drop fuse shall form an angle of 15% ~ 30% with the vertical line. The vertical distance from the bottom of the fuse at the low voltage side to the ground shall not be less than 3.5m, and the horizontal distance of each phase fuse shall not be less than 0.2m.
The fuse of drop fuse switch shall be selected according to the principle of “rapid fusing in case of short circuit in distribution transformer or high and low voltage outlet pipes”, and the fusing time of fuse must be less than or equal to 0.1s. The capacity of distribution transformer is below 100kVA, and the rated current of fuse at high voltage side is selected according to 2 ~ 3 times of the rated current of transformer capacity; The capacity is above 100kVA, and the rated current of high-voltage fuse is selected according to 1.5 ~ 2 times of the rated current of transformer capacity.
The fuse at the low-voltage side of the transformer shall be selected according to the rated current at the low-voltage side. Most of the external factors affecting the operation of distribution transformer come from lightning accidents. Therefore, when installing lightning protection device for transformer, metal oxide surge arrester with gapless synthetic insulation jacket shall be selected, which has strong power frequency voltage withstand capacity, good sealing and stable protection characteristics. In phase I rural power network, it is found that many lightning arresters are installed on the transformer (at the porcelain bushing on the high-voltage side), and the lightning arresters are connected with iron plates. This practice is wrong.