Random Separation - Development and Experience

The joint burial of primary power and telephone distribution cables with no deliberate separation is known as random separation. After extensive tests, the Joint Edison Electric Institute- Bell System Subcommittee to Study Buried Distribution Systems recommended random separation between telephone cables and certain types of primary power cables having bare neutrals in direct contact with the earth and protected by devices capable of clearing faults within prescribed time-current limitations. There has been favorable experience with over 18 million trench feet of random construction serving more than 200 000 dwelling units. The National Electrical Safety Code and state regulations have been revised to permit random separation.