If data is not available or accessible for protective devices such as relays, circuit breakers and fuses, but reasonable assumptions can be made as to the device type or characteristics, these assumptions may be used. Care should be taken to ensure that the assumptions do not lead to under-reporting of available incident energy at downstream equipment. An alternate to this is to use the next over-current device upstream to define the clearing time where the data is known. It is assumed that devices are installed and maintained per their manufacturers' recommendations, are in good working order, and will trip according to their published time-current characteristic curves. The devices should not be considered in the arc flash study until they are in proper working order.
If actual utility available fault current cannot be obtained from the utility company, then alternate scenarios should be modeled considering minimum and maximum values of utility fault current. These scenarios will provide a range of utility fault contributions that the study can be based on to account for potential changes in the utility system, and allowing for calculation of worst case arc flash levels inside the facility. Actual equipment data of bus gaps should be used if available to provide accurate results of the expected incident energy. Utilize default values provided in IEEE Standard 1584 only if actual values are not available. Document that the study is based on default values because actual bus gaps were not available.
If manufacturer data is not available for transformers, motors, generators or cables, then reference data may be used.
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