The protection of a three phase distribution transformer has a dielectric insulation in a liquid comprising a switch disconnector phase

摘要

P the protection system of a three-phase distribution transformer immersed in a dielectric liquid contained in a tank (6) comprises, on two (3, 4) of the three phases of the high voltage side of the transformer, a current-limiting fuse (19, 20) and a micro - fuse (21, 22) of protective fuse arranged in series with the current limiter. The micro - fuse is faster than the current-limiting fuse, and is associated with a striker pin (23, 24). It further comprises at least one means (32, 33) of the detection of a fault on at least one of the following points: the pressure in the tank and the level of the dielectric, a short - circuiter of the three-phase (29, 30, 31) located on the high voltage between said fuses current limiter and the high tension windings (1). The short - circuiter is controlled by said detection means of a fault and by the firing pin associated with each microphone - fuse. The third phase is equipped with the high voltage side of the transformer and upstream of the short - circuiter of a switch disconnector (39) which is normally closed in the absence of defects and the opening of which is triggered by the short - circuiter in the case of a defect, but with a certain delay so as to isolate the third phase only after the fuses by the short - circuiter. / p