Protection system for protecting a poly-phase distribution transformer insulated in a liquid dielectric, the system including at least one phase disconnector switch

摘要

The distribution transformer is installed in a station having N phases, at least N-1 phases being 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 protection system includes: 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 a controller for controlling said short-circuiter. In the system, 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.