This European Standard applies to the cathodic protection of complex structures. It is applicable to structures, which are to be cathodically protected, but cannot be electrically isolated, whether for technical or safety reasons, from foreign metallic structures situated in the same electrolyte as the structure to be protected. Such a structure is referred to as a "complex structure". This European Standard is not applicable to structures that can be protected in accordance with EN 12954. When contacts with foreign structures or defective isolation from foreign structures exist, but can be corrected, EN 12954 is applicable instead of this document. As an example pipeline network distribution systems are not considered to be complex structures It is assumed in this document that the design, installation, commissioning, inspection and maintenance are entrusted to adequately trained, experienced, competent and reliable personnel in order to achieve effective and efficient cathodic protection. Annexes A and B show the principle scheme of a complex structure with examples.