Underground distribution vaults with environmental control

Hydro-Quebec's underground distribution system in urban areas accounts for a total of nearly 2000 transformer vaults. Although all the utility's electrical equipment installed in them is submersible, these vaults are the scene of major operating and maintenance problems. Premature aging of the electrical equipment is also a source of concern, since the vaults do not provide any control over water infiltration and elimination. The ambient conditions are insanitary and conducive to accelerated corrosion. Hydro-Quebec therefore set up a multidisciplinary task force which, from 1993 to 1996, worked on a new and original concept of vaults with environmental control in an aim to reduce problem situations. So far, about thirty of these new vaults have been installed on the distribution system. However, a further development step has recently been taken in an aim to optimize the civil construction cost, which would improve availability and simplify the water control and drainage system, designed to meet stringent environmental regulations.