Arc Flash Hazard Analysis & Incident Energy
Incident energy measurement, factors affecting arc flash energy, DC arc flash, clearing time, fault current, and the 1.2 cal/cm^2 threshold.
- Define incident energy and its unit of measurement
- Identify factors that increase arc flash energy
- Explain the purpose and process of an incident energy analysis
- Describe how arc flash labels are maintained and updated
- Apply DC arc flash concepts and calculations
Lección 1
Incident Energy Fundamentals
What Is Incident Energy?
Incident energy is the amount of thermal energy per unit area at a specific working distance from an arc flash event. It is measured in cal/cm^2 (calories per square centimeter). This measurement determines the severity of potential burn injuries and drives PPE selection.
The significance of 1.2 cal/cm^2 cannot be overstated - this is the onset of second-degree burn threshold used to establish the arc flash boundary. At this energy level, unprotected skin will sustain a curable second-degree burn. Above this level, injuries become progressively more severe.
The Purpose of Incident Energy Analysis
An incident energy analysis calculates the cal/cm^2 at working distance to determine PPE selection. This analysis uses system parameters - voltage, available fault current, protective device clearing time, and working distance - to calculate the specific incident energy at each piece of equipment.
The results of an incident energy analysis are used to:
- Determine the required arc rating of PPE
- Establish the arc flash boundary distance
- Create equipment labels with hazard information
- Select between the incident energy analysis method or the PPE category (table) method
Exam Tip
The function of an incident energy analysis is to calculate cal/cm^2 at working distance for PPE selection. It does not calculate voltage drop, conductor size, or torque.
Incident energy is measured in cal/cm^2 and determines the severity of arc flash exposure. The threshold of 1.2 cal/cm^2 marks the onset of second-degree burns and defines the arc flash boundary.