Impact resistant compact cable

A cable for use in a predetermined voltage class, comprising:

• a conductor;
• an insulating layer surrounding said conductor;
• and
• a protective element around said insulating layer having a thickness and mechanical properties selected to provide a predetermined impact resistance capability, said protective element comprising at least one expanded polymeric layer,
• said insulating layer thickness being such as to provide a voltage gradient on the outer surface of the cable insulating layer not smaller than 1.0 kV/mm, and
• said protective element thickness being sufficient to prevent a detectable insulating layer damage upon impact of at least 25 J energy.

A cable for use in a predetermined voltage class, comprising:

• a conductor;
• an insulating layer surrounding said conductor;
• and
• a protective element around said insulating layer comprising at least one expanded polymeric layer, the protective element thickness having a value smaller than 7.5 mm for a conductor cross-sectional area greater than 50 mm2 and a value greater than 8.5 mm for a conductor cross-sectional area smaller than or equal to 50 mm2.

A group of cables selected for a predetermined voltage class and having different conductor cross-sectional areas, each cable comprising:

• a conductor;
• an insulating layer surrounding said conductor;
• and
• a protective element around said insulating layer comprising at least one expanded polymeric layer, wherein the thickness of said protective element is in inverse relationship with the conductor cross-sectional area.

A method for designing a cable comprising a conductor, an insulating layer surrounding said conductor and a protective element surrounding said conductor, said protective element including at least one polymeric expanded layer, comprising the steps of:

• selecting a conductor cross-sectional area;
• determining the thickness for said insulating layer compatible with safe operation in a predetermined voltage class on said selected conductor cross-sectional area in correspondence of one of a number of predetermined electrical limit conditions;
• selecting the maximum insulating layer thickness among those determined in said number of predetermined electrical limit conditions;
• determining a thickness of said protective element so that said insulating layer is not detectably damaged upon an impact on the cable by an energy of at least 50 J;
• and
• using said selected insulating layer and said determined protective element thickness in the design of a cable for said predetermined voltage class and selected conductor cross-sectional area.