The standard 3-phase 4-wire distribution voltage level is 230/400 V. Many countries are currently converting their LV systems to the latest IEC standard of 230/400 V nominal (IEC 60038). Medium to large-sized towns and cities have underground cable distribution systems.
The output from a transformer is connected to the LV busbars via a load-break switch, or simply through isolating links.
In densely-loaded areas, a standard size of distributor is laid to form a network, with (generally) one cable along each pavement and 4-way link boxes located in manholes at street corners, where two cables cross.
Recent trends are towards weather-proof cabinets above ground level, either against a wall, or where possible, flush-mounted in the wall.
Links are inserted in such a way that distributors form radial circuits from the substation with open-ended branches (see Fig. C3). Where a link box unites a distributor from one substation with that from a neighbouring substation, the phase links are omitted or replaced by fuses, but the neutral link remains in place. we are doing Installation & Distribution System.