This document supersedes IEEE Std 28-1972 (ANSI C62.1-1971) and revises many portions of the previous edition. Three new significant design tests have been added to determine: (1) The highest 1.2 x 50 standard impulse which the surge arrester will allow without sparkover (2) The effect of external contamination on sparkover (3) Surge arrester disconnector characteristics Additional substantive changes include: (1) New definition of prorated section (2) Revision of Table 1 to include a 25 kV distribution surge arrester and special ratings for rotating machine protection (3) Increase in maximum rate-of-rise for front-of-wave sparkover test (4) Expanded range of currents in the discharge voltage test (5) Reduced high current test for station surge arresters to 65 kA (6) Expanded Table 4 to include test values for 550 kV and 800 kV system surge arresters (7) General revision of pressure-relief test