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 . <EOS>