The descriptions of the standard transient recovery voltage (TRV) envelopes and ratings are changed in this amendment. This is applicable for ac high-voltage circuit breakers rated above 1000 V and on a symmetrical current basis. The capability limits of these circuitbreakers are 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 inthis amendment to IEEE Std C37.09-1999 are described in amendment IEEE Std C37.04b-2008.