1 Rated voltage kV 550 
           2 Rated current A 4000
           3 Rated short-time withstand current kA    63/3s
           4 Rated peak withstand current kA 160
           5 Rated lightning impulse withstand voltage kV Across open breaks 1675+450
           To earth 1675 
           6 Rated 1min power frequency
           withstand voltage kV Across open breaks 740+315    To earth 740
           7 Rated switching impulse
           withstand voltage kV Across open breaks 1175+450
           To earth 1300