5c Arc Flash Study Reports Interpretation.pdf

Arc Flash Hazard Reports

Arc Flash Hazard Reports Page 1

The following is provides to aid in reading and understanding the information provided in the Arc Flash Hazard Reports.

Arc Fault Bus Name: This is the ID Name of the buses faulted. MCC and panels scheduled are presented as buses. This bus represents the main bus within the MCC or panel.

Arc Fault Bus kV: The voltage of the bus being faulted (kilo-volts).

Upstream Trip Device Name: The ID Name for the upstream bus. When a bus is faulted, the software checks every protective device for the current contribution to the fault and selects the protective device that should be used in the calculation. This is a selectable option. If selected, the corresponding trip time of that upstream device is used and listed in the spreadsheet.

Upstream Trip Device Function: If the trip device is a relay, then the device function name is provided in this column. Examples of device functions are: 51/50, 51N, 50G, 49, etc.

Equipment Type: Describes the type of enclosure specified in the Bus Data. The available types are Switchgear, MCC/Panel, Open Air and Conductor. Anything else will be represented as “Other”

Gnd: The “X” mark in this column indicates if the IEEE equation used the coefficient for solidly grounded systems.

Arc Gap: Gap between the phase conductors. The gap can be specified according to enclosure type and voltage.

Bus Bolted Fault (kA): This is current passing through the trip device for a 3-phase bolted fault at the faulted bus. If there is only one branch then the fault current is equal to the current through the protective device. Otherwise, the current through the protective device is a smaller value. If the protective device is across the other side of a transformer, then the current flowing is scaled by the transformation ratio.

Bus Arc Fault (kA): This is the estimated current flowing through the trip device, which contributes to the total arc current. This value is used by the program to estimate the trip time. For calculating the incident energy, the total fault current at the faulted bus is used.

Trip Time (sec): Trip time for the protective device at the estimated arc current. Use of IEEE 1584 2 second rule is indicated by the whole number 2 without decimal component.

Opening Time (sec): Breaker opening time for HV breakers. After the relay trips, the HV breaker takes this amount of time to clear the fault. Fuses and LV breakers do not have opening time.

Arc Time (sec): Total duration of arc fault. This is the sum of Trip Time and Opening Time.

Estimated Arc Flash Boundary: The flash protection boundary distance in specified units. This value corresponds to the trip device.

Working Distance: Approximate working distance in specified units.

Arc Flash Hazard Reports Page 2

Incident Energy (cal/cm2): This is the incident energy from arc flash corresponding to the trip device.

The trip time associated with the trip device is used in the calculation. However, the arc current or fault current used is the total fault current on the faulted bus and not the current seen by the trip device. The rating of personal protective equipment (PPE) worn by workers should be based on this value.

Comments: This column provides additional explanatory information. Example when arc flash incident energy exceeds acceptable PPE protection limits the message “Do not work on energized equipment” will be displayed. Another example may be “No Viable Trip Device Found Upstream or in Bus Dialog” for conditions where arc flash incident energy cannot be determined.