![]() However, some calculation methods state the incident energy in units of Joules/cm 2. Incident energy is usually expressed in units of calories per cm2 (cal/cm 2) and is defined as heat energy that passes through every 1 cm 2. The amount of heat energy released immediately by an arc flash is called incident energy or incident energy. To determine the magnitude of the arc flash and its associated hazards, some basic definitions were made. The greater the current, voltage and time, the greater the calorie produced. ![]() We can see that calories are directly related to current (amperes), voltage (volts), and time. Heat energy is measured in units such as BTU, joules, or calories.Ĭalorie is the amount of heat energy needed to raise the temperature of one gram of water by one degree Celsius.Įnergy is equivalent to power multiplication with time, and power (watts) is equal to volts x Amperes. Arc flash produces high heat at the point of occurrence of the arc. To determine the potential effects of arc flash, we need to understand a few basic terms. The NFPA 70E is most popular standard as reference to conduct arc flash hazard or risk assessment. ![]() This article will discuss what the definition, hazard category and risk level of arc flash and arc blast is according to or based on NFPA 70E. Arc blast is an advanced phenomenon of arc flash events. The air and gas around the arc rapidly heats up and the conductor becomes steam which causes waves called arc blasts. It is four times the surface temperature of the sun. Temperature at the arc point can reach or even more than 35000 Fahrenheit. Arc flash is also a phenomenon that is usually caused by accidental connection between live conductors, or between live conductors and the ground. Arc flash definition according to NFPA 70E is the sudden release of unexpected heat and light energy produced by electricity passing through the air like a lightning.
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