Since the inception of the COMTRADE standard in 1991 (C37.111), only a small number of users were successful in using the playback of digital fault recorder data to analyze relay response to power system disturbances. The use of COMTRADE files for protection testing is still limited due to the users lack of familiarity with the standard. A good understanding of the COMTRADE standard allows the user to easily create a new file, or modify an existing file, to test the protection-Since the inception of the COMTRADE standard in 1991 (C37.111), only a small number of users were successful in using the playback of digital fault recorder data to analyze relay response to power system disturbances. The use of COMTRADE files for protection testing is still limited due to the users　lack of familiarity with the standard. A good understanding of the COMTRADE standard allows the user to easily create a new file, or modify an existing file, to test the protection