The Technical Cooperation Agreement between ISO and CEN (Vienna Convention) is a technical cooperation agreement between ISO and the European Standards Committee (CEN). After being formally approved by ISO`s Executive Board at its meeting on 16-17 May 1991 in Geneva on 27 June 1991 by the NEB Board of Directors, it replaced the technical information exchange agreement between ISO and CEN concluded in 1989 (Lisbon Agreement). Vienn`s „codified“ agreement was approved in 2001 by the ISO Board and the NEEC Board of Directors. Nevertheless, the Vienna agreement allows the CEN or ISO to carry out standardisation activities on the same subject if deemed necessary. The Joint ISO-CEN Coordinating Group of the Technical Boards plays an important strategic role in monitoring the implementation of the Viennese Agreement and consulting with the CEN`s Senior Technical Committee and the ISO Technical Technical Committee on all matters related to the Viennese Agreement, including the need for revisions. In September 2001, a revised version (version 3.3) of the „Vienna“ agreement was published, which reduced the agreement itself to the essential principles of cooperation between ISO and the NEC. Overall, the current version of international standardization gives priority and gives more importance to ISO leadership than previous versions. For example, ISO standards can only be revised under ISO`s direction, regardless of their origin. In 1996, CENELEC and the CIS signed the Dresden Agreement to create the framework for an intensive consensus process between the development of European and international standards in the electricity sector. In October 2016, the IEC, which publishes the vast majority of international standards for electrical and electronic equipment and systems, and CENELEC, their European equivalent, signed the Frankfurt Agreement, which will strengthen harmonisation between international and European standards. In order to avoid duplication between de-derisation at international and European level, to the benefit of contributors and users of standards, as well as to improve the effectiveness of standardisation at European and international level, CEN and CENELEC have signed agreements with their respective international partners, the International Standards Organisation (ISO) and the International Electrotechnical Commission (IEC) on the rules of cooperation.