Dropout Fuse

Fuse selection

     The selection of the fuse should ensure that the distribution transformer internal or the high and low voltage outlet pipe can be quickly fused when there is a short circuit. In practice, the following principles are often used for selection; if the capacity of the distribution transformer is below 160KV, the fuse should be 2-2% of the rated current of the transformer. 3 times to choose, distribution transformer capacity of 160KV and above, according to 1.5 to 2 times to choose.

     The selection of the fuse must also consider whether the fuse breaking characteristics can match the protection time of the first level. This is the key issue to determine whether the fuse protection can be effective. The quick-break protection action time of the distribution line is very short, about 0.1S About. According to the characteristic curve of the fuse, the current that breaks the fuse within 0.1S should not be less than 20 times the rated current. This data is a necessary condition to ensure the cooperation between the fuse and the head-end circuit breaker.

     In actual operation, for a substation with a short-circuit capacity above 50MVA, the 50-150mm2 aluminum wire is the main line, the distribution transformer below 1250KV within 1km from the substation, or the transformer below 800KVA within 2km, and the 10KM The short-circuit current at the outlet of the 400KVA transformer within 400KVA can reach more than 20 times the rated current of the fuse (the fuse is selected as 1.5 times). For the overcurrent protection of the distribution line, it is easier to cooperate due to the time when it operates. It can be seen from this , For most distribution transformers, fuses can be used for protection