Electric fence system for protecting a site with a defined perimeter against intrusion, comprising: - an electric generator, - a first electric fence wire section, which is arranged along at least one portion of said perimeter and which is connected electrically to said electric generator, - a first bar of which a first half is capable of being fixed to a support arranged along said perimeter, - a first guide, which supports said first electric fence wire section and which is coupled mechanically to said first bar, and wherein - said first guide comprises a first hollow isolator, which supports said first electric fence wire section, - said first guide comprises a first support, which is fixed to a second half of said first bar, - said first guide comprises an elastic element, which is electrically conductive, which is placed at least partially inside said first isolator and which is coupled mechanically both to said first isolator and to said first support, - said first guide comprises a conductive element, which is in electrical contact with said first electric fence wire section, characterised in that - said conductive element comprises a first portion, which at least partially surrounds said elastic element, - the electric fence system is designed such that said conductive element is at a different electric potential to said elastic element, - the electric fence system is designed such that said elastic element is capable of bending when a determined force is exerted on said first electric fence wire section, so as to cause an electrical contact between said elastic element and said first portion of said conductive element, - the electric fence system comprises a detection device designed to detect an electrical contact between said conductive element and said elastic element. - an electric generator, - a first electric fence wire section, which is arranged along at least one portion of said perimeter and which is connected electrically to said electric generator, - a first bar of which a first half is capable of being fixed to a support arranged along said perimeter, - a first guide, which supports said first electric fence wire section and which is coupled mechanically to said first bar, - said first guide comprises a first hollow isolator, which supports said first electric fence wire section, - said first guide comprises a first support, which is fixed to a second half of said first bar, - said first guide comprises an elastic element, which is electrically conductive, which is placed at least partially inside said first isolator and which is coupled mechanically both to said first isolator and to said first support, - said first guide comprises a conductive element, which is in electrical contact with said first electric fence wire section, - said conductive element comprises a first portion, which at least partially surrounds said elastic element, - the electric fence system is designed such that said conductive element is at a different electric potential to said elastic element, - the electric fence system is designed such that said elastic element is capable of bending when a determined force is exerted on said first electric fence wire section, so as to cause an electrical contact between said elastic element and said first portion of said conductive element, - the electric fence system comprises a detection device designed to detect an electrical contact between said conductive element and said elastic element.