This International Standard provides requirements for some type tests which are significant only when made on the entire group. It provides also a basic relationship between compatible ratings of traction transformer and converter(s), in order to provide minimum requirements for the choice of their ratings. Moreover it gives the minimum values to be considered in order to choose switching devices with characteristics suitable for the converter group(s) involved. Annexes provide useful information as a guide for the group designer. Table 1 indicates the components of a converter group and the relevant applicable standards.