Submerged transformers up to 40MVA require according to IEC 61936-1 (§ 8.6.2.) and NF C13-200, a watertight retention representing 100% of the volume of oil contained and under certain conditions of a natural extinguishing device type ERT®, EXTICOV™ or LHD®.

Beyond 40 MVA, the transformer must be equipped with a pit or recovery tank with a minimum capacity of 20% of the quantity of dielectric contained in the transformer (1), usually equipped with an extinguishing cover of the EXTICOV™ or LHD® type(2) in order to guarantee a rapid and natural extinction of the liquid dielectric if the oils were to remain trapped there.

This recovery tank must be connected to a separate recovery tank (remote pit), with a capacity at least equal to that of the highest capacity transformer, when it is common to several transformers (3).

Moreover, when the equipment is placed outside, rainwater or fire-fighting deluge systems fill this secondary retention tank. To evacuate this water and thus avoid any risk of overflow, the tank must be equipped with a system capable of filtering and continuously evacuating the drainage water while retaining the hydrocarbons inside the secondary containment. The water discharged must not be contaminated with more than 5 ppm of hydrocarbons according to the EN 858-1 standard ("light liquid separation installations").

The DEPOSIT® range of pits meet this need for rapid construction and passive treatment of drainage water.