IEC 62271-109:2008 is applicable to a.c. series capacitor by-pass switches designed for outdoor installation and for operation at frequencies of 50 Hz and 60 Hz on systems having voltages above 52 kV. It is only applicable to by-pass switches for use in three-phase systems. This standard is also applicable to the operating devices of by-pass switches and to their auxiliary equipment. This second edition cancels and replaces the first edition, published in 2006, and constitutes a technical revision. This standard is to be read in conjunction with IEC 62271-100 and IEC 62271-1 (2007), to which it refers and which is applicable, unless otherwise specified in this standard. The main changes with respect to the previous edition are listed below: - By-passing test duty has been split. - Equivalence regarding applicability of test parameters were reviewed. - Recovery voltage waveshape during insertion test duty has been recalculated and optimized. An explanatory note on the calculation of the recovery voltage is given in Annex F. - Withdrawal of the electrical endurance class BP2. Such devices are now covered in informative Annex E. - Addition of Annex D which gives examples of typical by-pass switch ratings.