Features of the new 138 kV self-contained oil filled cable system for Detroit Edison

The necessity for 200 mva underground cable circuits to supply two new 120/13.2 kV compact (SF6) mini-subs in Detroit was resolved in an innovative way by Edison. The duct and manhole system was designed for self-contained oll filled cables. The cable system incorporated sheath insulation and crossbonding to minimize sheath losses,and an oil pressurized supply system required cable sheaths capable of 35-40 psi nominal operating pressure. The first circuit featured lower cost, reduced size jointing manholes with a new cable clamping and restraint system. During the installation, a completely new MIG welded connector had to be developed for 2500 kcmil (1250 mm²) Aluminum conductor designed for this cable and this manhole system. Operating experience to date attests to the effectiveness and integrity of these new and economical advantages complementing the self-contained oil filled cable system.