Patent ID: 6839207

Claim:
A protection system for protecting a distribution transformer having N phases, the transformer being immersed in a liquid dielectric contained in a tank, in which at least N-1 phases are equipped on the high-voltage side of the transformer with respective current-limiting fuses capable of blowing in the event of a dead short circuit between the phases, the system comprising: at least one fault detector for detecting faults on the basis of at least one of the following indicators: pressure in the tank, level of the dielectric, or temperature of the transformer; a short-circuiter acting on all the phases situated upstream from the high-voltage windings, said short-circuiter being capable of being triggered by said fault detector to establish a dead short circuit between the phases; and on at least N-1 phases, a detector for detecting an abnormal current upstream from the transformer, said detector being associated with control means for controlling the triggering of said short-circuiter, wherein at least the phase that is not equipped with a limiting fuse is equipped with a disconnector switch which is normally closed in the absence of any fault, said disconnector switch being disposed on the high-voltage side of the transformer upstream from the short-circuiter, and opening thereof being triggered by the short-circuiter in the event of a fault, but with a certain delay relative to the triggering of the short-circuiter itself.