How to select requirements for fuses of distribution transformers

For distribution transformers with a capacity of 100kVA and below, the high-voltage side fuse should be selected as 2-3 times the rated current of the transformer. For those with a capacity above 100kVA, the high-voltage side fuse should be selected as 1.5-2 times the rated current of the transformer. The low-voltage side of the transformer should be melted The wire (sheet) is selected according to the rated current on the low-voltage side.


Some users’ high-voltage drop fuse is directly connected with aluminum wire or copper wire. On the low-voltage side, some thick copper wires are used to directly connect with the load switch (the copper wire is placed in the switch), which has no insurance function and no automatic air switch. In this way, when a short circuit or other fault occurs in the subscriber line or the transformer itself, the insurance will not work, the transformer will burn out, and the external power supply will be interrupted, even affecting the safe operation of the power supply department’s substation.



Therefore, here we again emphasize that high voltage must use drop insurance, and low voltage must use porcelain plug insurance or spiral insurance. Its capacity can be calculated according to the following empirical formula (applicable to 10 kV/0.4 kV Distribution change). That is, high-voltage insurance: its capacity divided by 10 is the capacity of its fuse.


For example, for a 100 kVA transformer, 100/10=10 (A) fuse should be selected. Low-voltage insurance: multiply its capacity by 2.


For example, a 100 kVA transformer should choose a 100×2=200 (A) fuse.

Post time: Nov-24-2021