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This standard is revised to change the descriptions of the standard transient recoveryvoltage (TRV) envelope and ratings. This is applicable for ac high-voltage circuit breakers ratedabove 1000 V and on a symmetrical current basis. The capability limits of these circuit breakersare determined to a major degree by the TRV. The revised descriptions of TRV bring the TRV requirements in IEEE standards into harmony with the TRV requirements in IEC standards that apply to the same type and class of equipment. The TRV revisions addressed in this amendment to C37.09 are described in amendment C37.04b-2008.