Home Page Frequently Asked Questions Like Share 928 Procedure for IEEE 1584 based arc flash calculations. SHORT CIRCUIT: SCA Software Label Maker Reference Data ARC FLASH: AFA Software Online Calc Comparison Video Tutorials SERVICES: Label Printing Info / FAQ Examples Newsletters Contact Us Testimonials Terms of Use News & Links Site Map Arc Flash Label Printing Services Normalized incident energy can be found using the equation below: lg En = K1 + K2 + 1.081 * lgIa + 0.0011 * G (1) En incident energy J/cm2 normalized for time and distance. The equation above is based on data normalized for a distance from the possible arc point to the person of 610 mm. and an arcing time of 0.2 sec. K1 = 0.792 for open configurations, and is 0.555 for box configurations / enclosed equipment. K2 = 0 for ungrounded and high resistance grounded systems, and equals 0.113 for grounded systems. G gap between conductors in millimeters. Ia predicted three phase arcing current in kA. It is found by using formula 2 a) or b) so the operating time for protective devices can be determined. For 1000V and lower systems: lgIa = K + 0.662 * lg Ibf + 0.0966 * V + 0.000526 * G + 0.5588 * V * lgIbf 0.00304 * G * lgIbf (2a) Arc Flash Software lg is logarithm base 10 (log10). Ia arcing current in kA. En normalized incident energy in J/cm2 as calculated by (1). K equals 0.153 for open configurations. and 0.097 for box configurations. Ibf bolted fault current for three phase faults in kA symmetrical rms. V system voltage in kV. G gap between condactors in millimeters. Solve lgIa = 0.00402 + 0.983 * lg Ibf (2b) for applications with a system voltage ranging from 1 up to 15kV. Incident energy can be found using the equation below: E = 4.184 * Cf * En * (t / 0.2) * (610x/Dx) (3) E incident energy exposure in J/cm2. Cf calculation factor equal to 1.0 for voltages above 1 kV, and Make $$$ and 1. the theoretically derived Lee method can be applied.2 cal/cm2 ) for bare skin. and incident energy can be determined using the equation below: E = 2. Cf calculation factor equal to 1. x distance exponent. Incident energy is measured in joules per centimeter squared .5 for voltages below 1 kV. t arcing time in seconds.142 * 106 * V * Ibf * (t / EB)]1/2 (6) DB distance of the boundary from the arc point in millimeters. Arc Flash Terminology Incident Energy Exposure This is the amount of thermal incident energy to which the worker's face and chest could be exposed at working distance during an electrical arc event. or at the rating of proposed personal protection equipment. Ibf is bolted fault current For the IEEE Std 15842002 empirically derived model.2) * (610x/EB)]1/x (5) For the Lee method: DB = [2. En normalized incident energy in J/cm2 as calculated by (1).0 for voltages above 1 kV. Ibf bolted fault current for three phase faults in kA symmetrical rms. D distance from possible arcing point to the person in millimeters. For cases where voltage is over 15 kV. or gap is outside the range of the model.184 * Cf * En * (t / 0. En normalized incident energy in J/cm2 as calculated by (1) above. Ibf bolted fault current EB is usualy set at 5 J/cm2 (1. arc flash boundary is calculated using the equation below: DB = [4.5 for voltages below 1 kV. EB incident energy in J/cm2 at the boundary distance.Join A Free Webinar 1. x distance exponent. t arcing time in seconds.142 * 106 * V * Ibf * (t / D2) (4) E is incident energy in J/cm2 V is system voltage in kV t is a arcing time in seconds D is distance from possible arc point to person in mm. 5 oz/yd^2. The arc flash boundary is required to be calculated by NFPA 70E. The Incident Energy at Arc Flash Boundary value should be equal or above incident energy to second degree burn for bare skin exposure. safety glasses. Energy. the Guide equation for arc flash boundary can be solved with other incident energy levels as well such as the rating of proposed personal protective equipment (PPE).2 cal/cm^2 for bare skin is used in solving equation for arc flash boundary in IEEE 1584 Guide for Performing Arc Flash Hazard Calculations. cal/cm^2 cal/cm^2 cal/cm^2 0 Eb 0 Eb + 0. Arc Flash Boundary The arc flash boundary is an approach limit at a distance from exposed live parts or enclosed live parts if operation. as evaluated in IEEE Standard 1584.001 and above Consult Not Available Recommended Personal Protective Equipment ( PPE ) Hazard Level Personal Protective Equipment ( PPE ) 0 Untreated natural fiber long sleeve shirt & pants with a fabric weight of at least 4. Hazard Level Rating of PPE. Minimum reported incident energy is 0. ear canal inserts. manipulation. .001 25 3 25 25.001 40 4 40 40. with the intent to protect the worker from the thermal effects of the arc flash at working distance from the source of the arc. heavy duty leather gloves. Incident Energy at Arc Flash Boundary A value in cal/cm^2 to determine arc flash boundary (AFB) distance at that Incident Energy. However.001 4 1 4 4.001 8 2 8 8. Hazard Level This is the minimum level of Personal Protective Equipment in calories per centimeter squared. The Incident Energy of 1. or testing of equipment creates a potential flash hazard. Min Incident Max Incident Required Min Energy.(J/cm2) or calories per centimeter squared (cal/cm2). within which a person could receive a second degree burn if an electrical arc flash were to occur.25 cal/cm2 which is the accuracy limit of the test equipment. A worker entering the arc flash boundary must be qualified and must be wearing appropriate PPE. Equipment Class Classes of equipment included in IEEE 1584 and typical bus gaps are shown in table below: Classes of equipment Open Air Lowvoltage switchgear 15kV switchgear 5kV switchgear Lowvoltage MCCs and panelboards Cable Typical bus gaps. AR jacket. hard hat. safety glasses. AR gloves.1 2 3 4 Arc rated (AR) shirt and AR pants or AR coverall. highresistance grounding and lowresistance grounding. mm 10 40 32 152 104 25 13 Gap between Conductors Equipment bus gap in mm. hard hat. hard hat. Grounding Type Two grounding classes are applied in the IEEE 1584 procedure. ear canal inserts. AR hood. hard hat. AR gloves. Gaps 13. safety glasses. 104 and 152 mm. leather footwear. the theoretically derived Lee method can be applied and it is now included in ARCAD's arc flash assessment software. Arc rated (AR) shirt and AR pants or AR coverall. leather footwear. leather footwear. AR jacket. . ear canal inserts. Arc rated (AR) coverall over AR shirt and AR pants. AR flash suit hood. AR flash suit. b) Solidly grounded. as follows: a) Ungrounded. were used in 5 and 15kV equipment testings. For cases where gap is outside the range of the Empirical model. safety glasses. heavy duty leather gloves. Working Distance Typical working distance is the sum of the distance between the worker standing in front of the equipment. which included ungrounded. and from the front of the equipment to the potential arc source inside the equipment. safety glasses. ear canal inserts. AR face shield. ear canal inserts. heavy duty leather gloves. leather work shoes. Gaps of 3 to 40 mm were used for low voltage testing to simulate gaps between conductors in low voltage equipment and cables. Multilayer arc rated (AR) flash suit over AR coverall over AR shirt and AR pants. AR flash suit hood. If so. enter 42. add to that time 15%. the manufacturer's timecurrent curves may include both melting and clearing time.01 seconds).35 into this box. For relays operating in their instantaneous region. Predicted 3 Phase Arcing Current The arcing current depends on the available 3 phase bolted fault current for the range of 700A to 106kA at the point where work is to be performed. use 0.350 amps are available. The head and body are a large percentage of total skin surface area and injury to these areas is much more life threatening than burns on the extremities. which can be found in manufacturer's data. mm 610 910 455 455 Arc Duration / Total Clearing Time Use protective device characteristics. the relay curves show only the relay operating time in the timedelay region. the program calculates the value based on the system parameters. Leave the field blank. Typical working distances are shown in table below: Classes of equipment Lowvoltage switchgear 15kV / 5kV switchgear Lowvoltage MCCs and panelboards Cable Typical working distance. allow 16 milliseconds on 60 Hz systems for operation. system voltage and gap between conductors. . Available 3 Phase Bolted Fault Current Available 3 phase bolted fault current for the range of 700A to 106kA at the point where work is to be performed is entered into this box in kA. not the incident energy on the hands or arms.01 seconds for the time. Please consider ARCAD's short circuit calculation software to determine the available fault currents in your power distribution system. configuration. If the arcing fault current is above the total clearing time at the bottom of the curve (0.03 seconds. If 16. Opening times for particular circuit breakers can be verifed by consulting the manufacturer's literature. The arc duration should be determined based on the predicted arcing current. If they show only the average melt time. the manufacturer's time current curves include both tripping time and clearing time. For relay operated circuit breakers.03 seconds to determine total clearing time. The circuit breaker opening time must be added. up to 0. For circuit breakers with integral trip units. use the clearing time.Arcfash protection is always based on the incident energy level on the person's face and body at the working distance. and 10% above 0. The degree of injury in a burn depends on the percentage of a person's skin that is burned. For fuses. Example: if 42.000 amps are available. enter 16 into this box. Incident energy is linear with time. the theoretically derived Lee method can be applied and it is now included in ARCAD's arc flash assessment software. ARCAD's arc flash assessment software makes possible both calculations for each case considered. This solution was developed by comparing the results of arc current calculations using the best available arc current equation with actual measured arc current in the test database. The solution is to make two arc current and energy calculations; one using the calculated expected arc current and one using a reduced arc current that is 15% lower. so arc current variation may have a big effect on incident energy. It requires that an operating time be determined for both the expected arc current and the reduced arc current. Effect of arc current variation on determination of clearing time For protective devices operating in the steep portion of their timecurrent curves. Write us at: . For cases where voltage is over 15kV. System Voltage System Line to Line Voltage for the range of 208V to 15000V is entered into the box in Volts. Incident energy is calculated for both sets of arc currents and operating times and the larger incident energy is taken as the model result. a small change in current causes a big change in operating time.